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General Category => Technical Support => Hardware related => Topic started by: Shining on 00:45, 13 January 15

Title: Fixing Floppy-Drives
Post by: Shining on 00:45, 13 January 15
As written here:

Wanted - 3" internal or external disk drive (http://www.cpcwiki.eu/forum/classifieds/wanted-3%27-internal-or-external-disk-drive/)

my two internal drives only produce read-errors. So I tried to let them be fixed without success.
My drives are back home now. The error-description was not headcrash for both but for one. They said the other has a damaged stepper-motor.
I retried both on my cpc and both stepper-motors are moving.

I would be very pleased if someone here will be able to fix one or both of them, because being completely without a working 3"-drive is a mess.

(My 3 1/2-drive and my hxc are still working so I'm not completely lost)

Title: Re: Fixing Floppy-Drives
Post by: Bryce on 10:20, 13 January 15
Send them to me. I'm Germany, so the postage shouldn't be too bad.

PM on its way to you...

Bryce.
Title: Re: Fixing Floppy-Drives
Post by: TFM on 18:35, 13 January 15
Well, if it can be done - then Bryce can do it.  :) :) :)
Title: Re: Fixing Floppy-Drives
Post by: paradroid90 on 19:12, 13 January 15
I second that TFM  :D
Title: Re: Fixing Floppy-Drives
Post by: CraigsBar on 01:35, 14 January 15
Thirded. Bryce really is the drive doctor. He fixed one of mine.
Title: Re: Fixing Floppy-Drives
Post by: Bryce on 09:59, 14 January 15
Application forms for my fan club can be downloaded at www.... :D

Thanks for all the words of approval guys.

Bryce.
Title: Re: Fixing Floppy-Drives
Post by: paradroid90 on 15:46, 14 January 15
lol  :D Do we get a free goodie bag if we join Bryce :-)
Title: Re: Fixing Floppy-Drives
Post by: CraigsBar on 15:48, 14 January 15
A free 464plus upgrade, and/or 3inch drive fix for the first 20 members LOL.
Title: Re: Fixing Floppy-Drives
Post by: Bryce on 16:30, 14 January 15
Yeah suuuuure. You get a signed photo of my soldering iron :D

Bryce.
Title: Re: Fixing Floppy-Drives
Post by: CraigsBar on 16:40, 14 January 15
Even your soldering iron can sign photos? Wow, you are clearly a genius, inventing and building a sentient soldering iron that can sign photos. I want one of those.
Title: Re: Fixing Floppy-Drives
Post by: Bryce on 17:17, 14 January 15
They will come... They will burn...

No of course not! That's the subtle difference between "of" and "by".

Bryce.
Title: Re: Fixing Floppy-Drives
Post by: CPC_Fan on 18:19, 14 January 15
I know that this is a bit cheeky, but you don't fancy a go at repairing my internal 3" drive at all do you Bryce? It currently will not read or write to discs for strange reason. The belt looks fairly new and is intact, so I don't think that is the problem.

As an alternative, I could send the whole computer and maybe you could fit an Amsdos/Parados ROM internally, that could switch between the two of them? The Amsdos ROM is in a socket by the way. The only thing with that of course, is that the cost of posting the whole computer from the UK to Germany could be too expensive  :o  Also I would need it back asap.

What do you think Bryce?
Title: Re: Fixing Floppy-Drives
Post by: CraigsBar on 19:25, 14 January 15
They will come... They will burn...

No of course not! That's the subtle difference between "of" and "by".

Bryce.

I was thinking that a signed picture is normally signed by the subject matter. But anyway it seems the humour/sarcasm was lost... Does this mean we don't get any signed soldering iron porn
Title: Re: Fixing Floppy-Drives
Post by: CraigsBar on 19:28, 14 January 15
I know that this is a bit cheeky, but you don't fancy a go at repairing my internal 3" drive at all do you Bryce? It currently will not read or write to discs for strange reason. The belt looks fairly new and is intact, so I don't think that is the problem.

As an alternative, I could send the whole computer and maybe you could fit an Amsdos/Parados ROM internally, that could switch between the two of them? The Amsdos ROM is in a socket by the way. The only thing with that of course, is that the cost of posting the whole computer from the UK to Germany could be too expensive  :o  Also I would need it back asap.

What do you think Bryce?
if the amsdos Rom is socketed then I can happily burn and post a Parados Rom to you for a direct swap upgrade.

That way you only need to post the drive to Germany. PM me if interested
Title: Re: Fixing Floppy-Drives
Post by: CPC_Fan on 19:59, 14 January 15
Hmm... food for thought... Thanks Craig. I will have a think and let you know.

Mark
Title: Re: Fixing Floppy-Drives
Post by: TFM on 20:47, 14 January 15
... I will have a think and let you know.

... I will have a drink too then  ;)
 
Title: Re: Fixing Floppy-Drives
Post by: CPC_Fan on 22:06, 14 January 15
Eh??
Title: Re: Fixing Floppy-Drives
Post by: CraigsBar on 22:23, 14 January 15
I think @TFM is in father jack mode lol. Drink!
Title: Re: Fixing Floppy-Drives
Post by: TFM on 00:35, 15 January 15
"Think" "Drink" - oh well, one can mix up some letters at this time of the day.  :laugh:
Title: Re: Fixing Floppy-Drives
Post by: CPC_Fan on 00:48, 15 January 15
Doh... Lol
Title: Re: Fixing Floppy-Drives
Post by: Bryce on 10:38, 15 January 15
I know that this is a bit cheeky, but you don't fancy a go at repairing my internal 3" drive at all do you Bryce? It currently will not read or write to discs for strange reason. The belt looks fairly new and is intact, so I don't think that is the problem.

As an alternative, I could send the whole computer and maybe you could fit an Amsdos/Parados ROM internally, that could switch between the two of them? The Amsdos ROM is in a socket by the way. The only thing with that of course, is that the cost of posting the whole computer from the UK to Germany could be too expensive  :o  Also I would need it back asap.

What do you think Bryce?

You can send the drive over of course. I'll send you a PM with my address. As far as the ROM is concerned, you can either take up Craigs offer, or (as you ROM is already socketed) it would be also possible to make a ROM/socket with switch that would plug into your PCB socket. This would give you a switchable AmsDOS/ParaDOS which I could easily just send back with the drive. You'd just have to mount the switch somewhere on the outer case (this just involves drilling a 6mm hole).

Bryce.
Title: Re: Fixing Floppy-Drives
Post by: CPC_Fan on 20:07, 15 January 15
Thank you Bryce. That would be most kind of you. I like the idea of a switchable AmsDOS/ParaDOS ROM, so if you could send one back with my drive when I send it to you, that would be very much appreciated. I take it that I would just be able to mount the switch to the case somewhere, as I don't own a soldering iron and therefore can't do any soldering?
Anyway if you could send me a PM with your address, I will send you my drive as soon as I can.
Thanks once again.
Mark
Title: Re: Fixing Floppy-Drives
Post by: Bryce on 21:55, 21 January 15
Hi Shining,
        your drives arrived today. I took the first one out and a 2 Minute visual check has already spotted the problem. Almost all the header connectors (to motors/sensors etc) have seriously bad dry joints. That guy never even looked at these! Anyone with half a clue about electronics would spot that instantly. I usually re-solder these as a matter of process, just because they cause problems so often.

Time to check the second one....

Bryce.

P.s. Thanks for the Gummibärchen. If I'm really quick I might even get one before my son (3) spots them.

Edit: Nothing obvious with the second drive. I'll power it up at the weekend to find out a bit more.

Here's what that guy supposedly didn't spot!! This is the header coming from the Index sensor, so it would definitely make the drive a non-runner.
Title: Re: Fixing Floppy-Drives
Post by: CraigsBar on 22:52, 21 January 15
Looks like Bryces "Drive Hero" status is intact.


Sheesh, looking at that picture I'm not sure how it ever worked.


Craig



Title: Re: Fixing Floppy-Drives
Post by: Shining on 23:00, 22 January 15
Whow. Thanks Bryce, why didn't I've asked here before ?

Don't know which of the two floppys this was but both are not the ones I had in my CPC when I bought my 6128 as a twelve years old boy in cologne. (That floppy died in the 80s). I'll never forget when we went to Saturn (at that time they existed only there) to buy one but they did not have one. I only spotted some games there including Batman (the first one). We went through the whole city searching another 6128 and finally found one at Quelle. Then we went back to Saturn (carrying the CPC and the GT65), bought Batman and Scooby Doo at Saturn and drove back home.

The CPC still exists and thanks to Bryce it will get a working floppy again....
Title: Re: Fixing Floppy-Drives
Post by: CPC_Fan on 19:32, 23 January 15
Bryce - I know that you are a busy person, but is there any chance that you could PM your address please, so that I can send my drive over for you to look at?
Title: Re: Fixing Floppy-Drives
Post by: Bryce on 15:44, 24 January 15
@Shining (http://www.cpcwiki.eu/forum/index.php?action=profile;u=922) : The first of the two drives is up and running now. I'll use it for a few days to make sure it stays that way. The main problem was the dry joints and a dodgy connection to the head position motor. The belt seems to be the original but it works ok still, although it has a bit a bend in it from not being used for so long. I can put a new one on if you want though?

The other drive is a bit questionable. After fixing the dry joints, it spins at the correct speed and the head is searching, but there is a lot of play in the head movement due to it being old, was used a lot and also looks like it was stored in a damp place at some time. I'll try to convince it to work again, but it may be a lost cause.

Bryce.
Title: Re: Fixing Floppy-Drives
Post by: gerald on 16:21, 24 January 15
The other drive is a bit questionable. After fixing the dry joints, it spins at the correct speed and the head is searching, but there is a lot of play in the head movement due to it being old, was used a lot and also looks like it was stored in a damp place at some time. I'll try to convince it to work again, but it may be a lost cause.
What model is this drive ?
On the EME156V, the spring that is part of the head motor can get week and fail to compensate the play of the tread mounting.
This can be fixed by disassembling the motor and slightly bending the metal bit that act as spring. You obviously need to align the head after.
You can check that play by monitoring the head signal amplitude on a selected track. When accessing it upward or backward the amplitude will be significantly different.
Title: Re: Fixing Floppy-Drives
Post by: Bryce on 16:57, 24 January 15
I managed to tighten up the spindle that moves the head and it's reading disks again :) So both are back working.
I'm not sure how reliable this drive will be, because the whole frame that holds the disk is a bit rusted and sticks quite a bit. I disassembled it, gave it a clean and re-greased it, but it's still not great. I'll use it for a few days and see how it gets on.

@Gerald : It's an EME150A, the one where the spin speed is a poti on the PCB, not in the motor. The more reliable one is an EME-155.

Bryce.
Title: Re: Fixing Floppy-Drives
Post by: gerald on 17:53, 24 January 15
I managed to tighten up the spindle that moves the head and it's reading disks again :) So both are back working.
I'm not sure how reliable this drive will be, because the whole frame that holds the disk is a bit rusted and sticks quite a bit. I disassembled it, gave it a clean and re-greased it, but it's still not great. I'll use it for a few days and see how it gets on.

@Gerald : It's an EME150A, the one where the spin speed is a poti on the PCB, not in the motor. The more reliable one is an EME-155.

Bryce.
Ok, that's a completely different mechanism.
By the way, do you have suggestion on a replacement for the woolen pad that press the disk on the head ? I have a non working drive that is missing this bit, and it took me a while to notice it  ;D
Title: Re: Fixing Floppy-Drives
Post by: Bryce on 18:11, 24 January 15
I've had to replace this once on a drive where the owner thought it was dirt and "cleaned" it off :D
I used a very fine felt sticker and that worked great, but I can't remember where I got it from, just be careful that
it's made of something very fine. Maybe the little cloth used to clean glasses ("Lunette" not "Verre" :)) with
some double-sided tape would work?

Bryce.
Title: Re: Fixing Floppy-Drives
Post by: CraigsBar on 19:04, 24 January 15
As a temporary measure, I replaced one of those with the similar pad from an audio cassette in about 1994. It's still in place, and still works perfectly.
Title: Re: Fixing Floppy-Drives
Post by: Bryce on 13:09, 25 January 15
Where are these used in audio cassette players??

Update on the floppy repair: The EME-150A is proving to still be very unreliable. I tried it this morning and it can't find the tracks any more. The EME-155 is still working fine.

Edit: Doh! Turns out I was testing it with a damaged floppy! Both still work fine :)

Bryce.
Title: Re: Fixing Floppy-Drives
Post by: CraigsBar on 14:43, 25 January 15
Where are these used in audio cassette players??

Update on the floppy repair: The EME-150A is proving to still be very unreliable. I tried it this morning and it can't find the tracks any more. The EME-155 is still working fine.

Edit: Doh! Turns out I was testing it with a damaged floppy! Both still work fine :)

Bryce.
no in the player, but in the cassette themselves, on a little leaf spring to press the tape onto the head.
Title: Re: Fixing Floppy-Drives
Post by: Bryce on 15:01, 25 January 15
Oh yeah, forgot about those. Good idea, it's exactly the right material.

Bryce.
Title: Re: Fixing Floppy-Drives
Post by: Shining on 23:30, 26 January 15
Thank you very much Bryce for fixing both drives ! After the first repair attempt failed, I was praying that at least one was fixable. Now that there are both fixed, I'm happy as hell  :-* .
Title: Re: Fixing Floppy-Drives
Post by: Bryce on 23:33, 26 January 15
No problem. I'm just happy that they were both saveable. I hate to see hardware that unrepairable.

Bryce.
Title: Re: Fixing Floppy-Drives
Post by: Shining on 22:43, 31 January 15
Again thank-you, Bryce. The drives arrived back today and now I'm re-assembling my 6128.
Title: Re: Fixing Floppy-Drives
Post by: Bryce on 11:17, 01 February 15
Cool. Despite all the modern solutions, it's still always nice to have a real floppy drive :) Glad I could help.
Let me know how long the older one lasts.

Bryce.

Gesendet von meinem Motorola DynaTEC 8000X mit Tapatalk 2.

Title: Re: Fixing Floppy-Drives
Post by: CPC_Fan on 18:28, 03 February 15
Bryce - I was just wondering if you could confirm whether or not you have received my 3" drive yet? I know that you have been away, so I wasn't expecting you to have had a look at it yet, but I was hoping that you have received it in one piece?


Mark
Title: Re: Fixing Floppy-Drives
Post by: Bryce on 22:50, 03 February 15
No not yet. What date did you send it?

Bryce.
Title: Re: Fixing Floppy-Drives
Post by: CPC_Fan on 17:54, 04 February 15
Oh that's odd. I sent it on the 26th of January. I have sent you a PM anyway.
Title: Re: Fixing Floppy-Drives
Post by: Bryce on 23:05, 04 February 15
I wouldn't worry about it yet. It usually takes up to 10 days from the UK and we are only at 7 today.

Bryce.
Title: Re: Fixing Floppy-Drives
Post by: Bryce on 11:40, 10 February 15
I'm happy to say, that after much research (from CPC_Fan) and a stroll around a few shops by myself, I finally have CPC_Fans drive :) Now to find out whether it's fixable...

Bryce.
Title: Re: Fixing Floppy-Drives
Post by: CPC_Fan on 14:10, 10 February 15
Glad to hear that you have finally got my drive Bryce. Hopefully once you have had a chance to look at it, it will be fixable.

Mark
Title: Re: Fixing Floppy-Drives
Post by: TFM on 19:35, 10 February 15
Hey guys, this is not facebook. For that kind of talk we got something here they call a PM!  :laugh:  Never mind.  :)
Title: Re: Fixing Floppy-Drives
Post by: Bryce on 22:06, 10 February 15
Hey guys, this is not facebook. For that kind of talk we got something here they call a PM!  :laugh:  Never mind.  :)

?? The thread is "Fixing Floppy-Drives" and the current conversation regards the logistical details of such a drive being sent for repair. We're not even off-topic! Where's the problem?

Bryce.
Title: Re: Fixing Floppy-Drives
Post by: TFM on 22:41, 10 February 15
It's just using up my scarce spare time if I have to read 10 times "Oh I did send you a floppy", "Oh, it must be still on the way". This is absolute off-topic. A purely private conversation, and probably getting on the nerves of others as well.  :-\
If I read the thread then I expect help in fixing floppies and not pages of private talk.  ::)


Sorry, but somebody had to say it.  :)
Title: Re: Fixing Floppy-Drives
Post by: Bryce on 23:27, 10 February 15
Nobody's forcing you to read it. If it doesn't interest you, then go read something else!?  :D

Just for you, number 11:

Hey CPC_Fan, just wanted to let you know that your drive has arrived. It looks to be in decent condition, probably just needs to be calibrated / aligned. I'll let you know later this week. Feel free to reply with a "Great let me know" message, don't bother with PM, let the whole thread know. :D

Bryce.

Title: Re: Fixing Floppy-Drives
Post by: TFM on 00:16, 11 February 15
Nobody's forcing you to read it. If it doesn't interest you, then go read something else!?  :D


I wished I *could*. But this is something the forum software is not capable of.

Title: Re: Fixing Floppy-Drives
Post by: Bryce on 19:47, 12 February 15
Hi CPC_Fan,
     how's the family... (oops, not facebook)...

Just fixed your drive. Turned out to be a few grains of dirt embedded into the head. The bad news is that it has probably destroyed any disk you've tried on it. It certainly shredded the surface of the disk I put in to try it  :( I managed to remove the dirt and polish the head and it's working fine now. On top of that, the wires from the index sensor were trapped in the loading mechanism. This didn't cause it to fail, but it wasn't helping either.

I'll try to get your drive back to the post by the weekend.

Bryce.
Title: Re: Fixing Floppy-Drives
Post by: CPC_Fan on 23:33, 12 February 15
Hi Bryce,


So glad to hear that the drive could be repaired and it was a relatively simple fix. Not sure how the dirt got embedded into the head or indeed how the wires from the index sensor got stuck in the loading mechanism? I hope that it didn't shred a disc that was of value when you tested it?


Would you still be able to make the switchable AmsDOS/ParaDOS ROM, complete with switch and socket that will go into my socket on the motherboard for me at all and send it back with the drive?


Anyway many thanks for looking at and repairing the drive for me Bryce, it is much appreciated.


Mark
Title: Re: Fixing Floppy-Drives
Post by: Bryce on 12:18, 13 February 15
Oh yeah, forgot about the ROM. Then give me another day or two to get that done then I'll send everything back together. I'd like to test the drive for another day or two anyway, because I found a disk last night that it had problems reading. It may need some minor further adjustment.

Yes, unfortunately it WAS a disk that I should have known better not to have put into a questionable drive. It was a "They Sold a Million" disk (with Jet Set Willy and Sabre Wolf). I'll just change the inards of the disk and re-copy the files over.

Bryce.
Title: Re: Fixing Floppy-Drives
Post by: CPC_Fan on 20:08, 13 February 15
That's ok Bryce. Not a problem if you need more time. I would rather that you was happy with it and sure that it was working properly, than send it back to me when it's not quite ready. Sorry that it ruined one of your discs. I obviously didn't mean for that to happen.


Mark.



Title: Re: Fixing Floppy-Drives
Post by: Bryce on 22:17, 13 February 15
Sorry that it ruined one of your discs. I obviously didn't mean for that to happen.

It's my own fault for doing something that stupid.

Bryce.
Title: Re: Fixing Floppy-Drives
Post by: TFM on 23:30, 13 February 15
No. IMHO one can't imagine that dirt destructs a disc. That's terrible. I'm sorry. to hear.
Title: Re: Fixing Floppy-Drives
Post by: pelrun on 10:51, 06 March 15
Looks like my drive just arrived at read-fail-land. Been having some PSU issues, so that may have hastened its demise. :(


Bryce, would you care to take a look at it for me please?
Title: Re: Fixing Floppy-Drives
Post by: Bryce on 11:45, 06 March 15
No problem. Have you checked what it will cost to get it to me?? Let's do some "Distant-Diagnostics" first (I'll send you a PM) to see if we can get it fixed without it leaving AU.

Bryce.
Title: Re: Fixing Floppy-Drives
Post by: pelrun on 14:05, 06 March 15
Well, looks like it was drive speed after all. My dodgy PSU must have been slowing the motor enough to have it mostly work; replacing it brought it up to 309 and stuff broke. Now it's reading 301 and even the previously marginal discs are ok again.


Cheers!
Title: Re: Fixing Floppy-Drives
Post by: Bryce on 14:52, 06 March 15
Great, fixed without a trip around the world :)

Bryce.

Edit: In case others are confused - I sent pelrun a list of stuff to check before he sent it all the way from AU to me.
Title: Re: Fixing Floppy-Drives
Post by: the KING on 21:01, 06 March 15
I really love the spirit here. Bryce, you seem to be a very kind person with all the help you provide.



Tom
Title: Re: Fixing Floppy-Drives
Post by: TFM on 21:53, 06 March 15
Interesting! How can you adjust the rpm's of a drive?

@Bryce (http://www.cpcwiki.eu/forum/index.php?action=profile;u=225): Would be nice if you can post this Drive-Check-List here too. Guess this will help a lot of people.  :)

Title: Re: Fixing Floppy-Drives
Post by: Bryce on 22:21, 06 March 15
@the KING (http://www.cpcwiki.eu/forum/index.php?action=profile;u=94) : The aim is to keep retro hardware alive, not to take peoples money. If I think something can be fixed "remotely", then that's the obvious first choice. If I suggest sending it to me, it's only because I don't think that the owner will be able to fix it with the tools / skills available.

@TFM (http://www.cpcwiki.eu/forum/index.php?action=profile;u=179) : There is an excellent page here from @gerald (http://www.cpcwiki.eu/forum/index.php?action=profile;u=250) that shows how to adjust the speed for all different types of CPC drive:  Amstrad FDD part - CPCWiki (http://www.cpcwiki.eu/index.php/Amstrad_FDD_part)
Together with the speed test software from @pacomix (http://www.cpcwiki.eu/forum/index.php?action=profile;u=855) : DskTest v0.1.47b (release?) (http://www.cpcwiki.eu/forum/applications/dsktest-v0-1b/) anyone can calibrate the drive spin speed themselves (if that's the problem).

My "Checklist" is normally just:

1 - Does it power on at all? (or cause the CPC not to boot if connected)
2 - Does the drive spin up?
3 - Does the head search (ie: move back and forth)
4 - Make strange noises?
5 - Have you checked that the belt is ok?

If I get a "No" on 1,2 or 3 or a "Yes" on 4, then I need it here - It's something more complicated. Otherwise I go through the steps of calibration and head cleaning with the user. If that doesn't solve the issue, then it still needs to be sent to me.

On Classic CPC drives, the most common problems are spin speed, head damage, worn out mechanics and electronic failure (in that order). On Plus drives there is an over-voltage diode that fails most often and after that it's the same failures as with the classic drives. The electronic failures are very often just dry solder joints and not parts that have failed. CPC drives are actually extremely robust.

Hope that has helped someone. Maybe I should do a drive repair page for the Wiki.

Bryce.
Title: Re: Fixing Floppy-Drives
Post by: Bryce on 22:01, 21 March 15
Another day, another drive. This one came from a user that was given it (for free as far as I know), but the previous owner has hacked away at it quite a bit, so I thought I'd share some pictures of some of the strangeness.
Other than being extremely dirty it supposedly could CAT a disk but doesn't load files, but I haven't connected it up yet, so I can't confirm that just yet. There were some (badly) re-soldered joints on the PCB and the LED pins were freely floating rather than soldered, but I fixed them before I thought of taking pictures. Here's the other stuff I found:

- The belt had been replaced with a tape drive (square belt), instead of the flat type needed. Not necessarily bad, but it rubs occassionally against the casing so the spin speed isn't stable.

 [ You are not allowed to view attachments ]

- Unfortunately he seems to have lost the write pin while he was at it, so it's a read-only drive at the moment too.

 [ You are not allowed to view attachments ]

- Now the best bit. If anyone can explain to me what this is meant to achieve, I'm all ears. This tiny pin (it's half of a bent sewing needle). Was heated and pushed into the plastic eject button. It also looks like it had been tried twice, or maybe there had been a second pin at one time that has since fallen out?? The eject button spring was rattling around on the top of the PCB, but that still doesn't explain the pin.

The pin:
 [ You are not allowed to view attachments ]

Where it was inserted:
 [ You are not allowed to view attachments ]

Although the drives frame is quite rusted, the drive head actually looks quite good after cleaning.
 [ You are not allowed to view attachments ]

So the drive can be saved. But it needs a new belt, a write pin, a resolder on the PCB connectors and LED, greasing on the frame and spindles and then it needs to be recalibrated. Of all the drives I've fixed lately, this is the first time I've asked myself, is it really worth it?[nb]Yes! Of course it's ALWAYS worth it :)[/NB]

Bryce.
Title: Re: Fixing Floppy-Drives
Post by: VincentGR on 22:23, 21 March 15
This is my drive  ;D

Yes, last October two friends gave me their cpcs.
One here in Pireaus and one 380km far from here where I work half of the year.
They know how wierd I am with old computers and they dig to find their chilhood machines for me.
I always buy and never sell.

The bad thing is that I forgot to bring the other cpc with me but I will send him on summer when I go back there.

Bryce, don't be surprised. Here electricians were only repair tvs, so I have seen wierd things too myself.

The best thing ever donated to me was an A500+ with ram expansion and a 1084 from my wifes friend.
She gave me the amiga the day of my marriage 4 years ago  ;D
Best present ever.
Title: Re: Fixing Floppy-Drives
Post by: Bryce on 22:29, 21 March 15
So I assume I should continue repairing this? I'm just glad he never tried to fix the 6128 you sent me, it's also a bit dirty, but at least no-one tried to fix it with "Voodoo Doll" methods :D

Bryce.
Title: Re: Fixing Floppy-Drives
Post by: VincentGR on 22:34, 21 March 15
So I assume I should continue repairing this? I'm just glad he never tried to fix the 6128 you sent me, it's also a bit dirty, but at least no-one tried to fix it with "Voodoo Doll" methods :D

Bryce.

Wait till u see the other cpc.
I saw the bottom pcb and it has custom traces...
Then u ll reconsider about the voodoo method    :D
Title: Re: Fixing Floppy-Drives
Post by: Bryce on 17:48, 22 March 15
Drive fixed except for write-pin replacement, now CATting and reading any floppy I care to try. I'll do the write-pin later in the week when I have time.

Bryce.
Title: Re: Fixing Floppy-Drives
Post by: pelrun on 16:45, 01 June 15
I finally got the 6128 out again with the goal of dumping all my disks to images for use with the Gotek I just flashed with HXC.


Can't get the gotek working; permanent disk missing error no matter what I do with the configuration or cabling. Ugh.


Disk drive starts throwing read fail errors. Ugh. At least this one I know how to fix, so I jump through all the hoops to load DskTest from my tape cable and tune the drive speed.


Drive speed doesn't change, then it changes by 60 rpm, then it doesn't change, then it goes to 500rpm permanently, then I manage to BREAK OFF THE TRIMPOT INSIDE THE DRIVE MOTOR.


AAAUUUUUUGGHHHH.


Moral of the story - make sure you use a *narrow* flat head screwdriver. This time around I used one that was way too wide; even though it fit in the adjustment hole it didn't fit in the slot in the trimpot.


I popped the top off the motor and had a look inside; apart from the free-floating trimpot and a couple of bent brush fingers everything seems ok. I'll get a replacement 10k pot tomorrow and see if I can't successfully reassemble the thing. I don't expect it to last; I just want it to run long enough to get those disks dumped...
Title: Re: Fixing Floppy-Drives
Post by: pelrun on 13:21, 03 June 15
I managed to repair the motor and get it reassembled - a somewhat tricky endeavour, as you have to remove the capstan and get the spinny thing out to safely get the commutator together without damaging the brushes. Anyway, a sharpened nail and hammer did the trick.

And now the drive makes a horrible squeaky noise, almost certainly due to the motor running backwards. Just to check - discs are meant to spin clockwise, right?

I'm going to hate pulling this motor apart again just to swap the brushes over...
Title: Re: Fixing Floppy-Drives
Post by: Bryce on 13:59, 03 June 15
How did you manage to get the motor running backwards?? Have you connected the wires the wrong way around?

Bryce.
Title: Re: Fixing Floppy-Drives
Post by: pelrun on 03:59, 04 June 15
As there's a speed controller inside the motor reversing the external wires won't work. The only thing it can possibly be is I got the brushes going the wrong way around the commutator ring, which is nuts because there's a very obvious brass contact patch on one side of each brush.


I've little choice (beyond sourcing another motor) but to open this one back up and swap the brushes over.
Title: Re: Fixing Floppy-Drives
Post by: pelrun on 05:41, 06 June 15
Opened the motor up again and swapped the brushes over, checked the motor runs the correct way, then tried again. It works!

Title: Re: Fixing Floppy-Drives
Post by: Bryce on 10:36, 20 October 16
Hi all,
   sorry for resurrecting a relatively old thread, but I thought I'd keep this information all in one thread to make it easier to find...

Last night I recieved two floppy drives for repair. Once again the owner informs me that he sent them to Dataserve for repair and they were returned as "unrepairable". I haven't tried to fix them yet, but even a simple first look tells me that the guy didn't even attempt to repair them. There are obvious dry joints on the header connectors and the motor capstan is full of gunk from the old belt. So he obviously just blindly swapped the belt and sent it back and he also obviously doesn't have the first clue about electronics. He did however charge for a supposed attempted repair.

So my message once again is DON'T SEND DRIVES TO DATASERVE FOR REPAIR. He is NOT repairing them, he's blindly swapping the belt without even cleaning the wheels and then sending them back as unrepairable if that hasn't solved the problem. And charging you good money for it.

Bryce.
Title: Re: Fixing Floppy-Drives
Post by: Gryzor on 14:53, 24 October 16
That's a shame, kind of you to let everyone know. Do we know how much it was for the "attempt"?
Title: Re: Fixing Floppy-Drives
Post by: Bryce on 15:04, 24 October 16
Just a quick update on the latest two patients: No. 1 was a relatively easy fix: Remove old belt gunk, re-solder a few dry joints, calibrate rpms and re-align head. Now fully and reliably working again.
Unfortunately No. 2 really is in a sorry state. There is serious corrosion on the PCB, most likely water damage. It looks bad, but all connections seem to be still there. There's also quite a lot of rust on the metal parts. It also seems to have had some extensive repair work done in the distant past (not done by Dataserve), the cable to the head has been replaced. I can get the rpms stable at 300, but the head mechanism is badly worn and the head has quite a bit of "wiggle", meaning that it rarely lines up to the same point twice. I have tried every tweak I can think of and will completely dis-assemble and rebuild the drive over the next few weeks, hopefully with some spare parts that I hope to get from a destroyed drive, but I don't hold up much hope for it. Looks like I may be looking at the first ever drive that I couldn't manage to fix :(

Bryce.

@Gryzor (http://www.cpcwiki.eu/forum/index.php?action=profile;u=1): The owner did get a refund for the "attempt", but he was still left with the bill for shipping two drives to the UK and back.
Title: Re: Fixing Floppy-Drives
Post by: CanonMan on 16:30, 24 October 16
No. 1 was a relatively easy fix: Remove old belt gunk, re-solder a few dry joints, calibrate rpms and re-align head. Now fully and reliably working again.


I hope you don't mind me asking, but what tools/procedure do you use to realign the head?


I had a couple of drives that had all the other bits you mention done to them, but they were still not reading reliably. Maybe I should dig them out (if I haven't already binned them!) and have another look at them.
Title: Re: Fixing Floppy-Drives
Post by: Bryce on 17:22, 24 October 16

I hope you don't mind me asking, but what tools/procedure do you use to realign the head?


I had a couple of drives that had all the other bits you mention done to them, but they were still not reading reliably. Maybe I should dig them out (if I haven't already binned them!) and have another look at them.

All drive repairs are done with an oscilloscope, a screwdriver, the DSKTest software, "tongue at the right angle" and lots of experience.

I really hope you haven't dumped good drives because of a badly aligned head!

Bryce.
Title: Re: Fixing Floppy-Drives
Post by: CanonMan on 18:42, 24 October 16
All drive repairs are done with an oscilloscope, a screwdriver, the DSKTest software, "tongue at the right angle" and lots of experience.

I really hope you haven't dumped good drives because of a badly aligned head!

Bryce.


Do you have the proper alignment disk? That's the only thing that's holding me back, I've got a scope and all the other bits!
Title: Re: Fixing Floppy-Drives
Post by: ||C|-|E|| on 19:15, 24 October 16
All drive repairs are done with an oscilloscope, a screwdriver, the DSKTest software, "tongue at the right angle" and lots of experience.

I really hope you haven't dumped good drives because of a badly aligned head!

Bryce.

In my experience, the position of the tongue is absolutely essential for most of the repair works. I employ the technique all the time, and it is the same when parking the car.
Title: Re: Fixing Floppy-Drives
Post by: Bryce on 23:18, 24 October 16

Do you have the proper alignment disk? That's the only thing that's holding me back, I've got a scope and all the other bits!

No, I just use a selection of commercial game disks. If you line it up to those you know it will work with disks from any other drive that's properly aligned.

Bryce.
Title: Re: Fixing Floppy-Drives
Post by: tjohnson on 18:46, 26 April 17
Looking for a bit of assistance.  I have replaced the belt in my drive on my new (to me) 6128, it had gone all horrible and sticky, it now spins the disc nicely but unfortunately the read head is not moving at all, it doesn't make any horrible noises at all and doesn't appear to attempt to move and I get a "bad command" returned when running CAT etc.  I wonder if this was the reason the computer was retired off some years back.  I have done some very basic checks and the monitor is delivering a fraction under 12v (11.9v) at the pcb header onto the mainboard (not the FDD).  Ive had a quick look at the service manual and it doesn't seem to give a great deal of info on the FDD other than replace it  The FDD board looks in good physical order no obvious corrosion, reading through this thread looks like I need to examine the PCB for dry solder joints.  The drive is an EME-155.  Can anyone give any hints on what to check next.
Title: Re: Fixing Floppy-Drives
Post by: Bryce on 22:11, 26 April 17
I'd definitely check for dry joints on the power connector on the drive PCB and then on the connector that goes to the drive head motor. Both of these are known for dry joints and would give the results you're observing.

Bryce.
Title: Re: Fixing Floppy-Drives
Post by: tjohnson on 03:05, 27 April 17

Thanks Bryce, had a look tonight, the solder joints look ok to me, couple maybe aren't 100%, what I did notice is a small bit of plastic by the electrolytic capacitor by the power connector right at the bottom.  In my photo you can still see a tiny bit.  I'm wondering if this has failed and could be causing the issue. 






Title: Re: Fixing Floppy-Drives
Post by: Audronic on 07:48, 27 April 17
Bottom Photo (FDD 1.jpg) Pin 1 on CN5 is suspect ?


Ray
Title: Re: Fixing Floppy-Drives
Post by: Bryce on 10:15, 27 April 17
Yup, CN4 probably isn't great either. These could be your problem.

Bryce.
Title: Re: Fixing Floppy-Drives
Post by: tjohnson on 10:45, 27 April 17
Yeah thanks both, now its morning and not the middle of the night I've taken a good look at CN3, CN4 and CN5 as you've both pointed out, they are quite shallow and have little solder on them, and all three appear to have suspect joints.  Will fire up the soldering iron later and fingers crossed, would be fantastic to get the drive working again.
Title: Re: Fixing Floppy-Drives
Post by: tjohnson on 03:07, 28 April 17
Soldering done, unfortunately no change.  Disc spins but the head stays stationary.  damn.
Title: Re: Fixing Floppy-Drives
Post by: Bryce on 10:19, 28 April 17
What equipment have you got to make further measurements?

Bryce.
Title: Re: Fixing Floppy-Drives
Post by: tjohnson on 11:56, 28 April 17
Unfortunately not a lot, i have a Multimeter but nothing more advanced.  What would be your next steps?  I have a friend who may be able to help with additional test equipment.

Sent from my E5823 using Tapatalk

Title: Re: Fixing Floppy-Drives
Post by: Bryce on 12:03, 28 April 17
The next step would be to follow the signals:

- Check if step signals are being sent from the FDC, then to the output logic, then to the STEP pin of the floppy drive and and finally what signals are going to the motor.

That way you can find out where it's going wrong.

If you don't have the equipment or knowledge to do this, you can send me the drive for repair.

Bryce.
Title: Re: Fixing Floppy-Drives
Post by: tjohnson on 02:04, 29 April 17
Hi Bryce thanks for the advice again,  I've ordered a logic probe which might help me check that is going on as you suggest.  I looked at the circuit diagram for the seek and direction pins on the fdc and can see they are going through a couple of logic gates.  I figured the price would allow me to check whether they are going high low or pulsing and whether there is anything stuck and the probe is cheap so not alot to lose.   Thanks for the offer of repair it may come to that.  If i had another drive at least it would confirm if the signal is arriving from the fdc and that the fault is on the drive.

Sent from my E5823 using Tapatalk

Title: Re: Fixing Floppy-Drives
Post by: tjohnson on 02:00, 03 May 17

Hi all,
well the latest on the drive is some progress.  I got the logic probe and I believe the signals are all ok, with the seek signal activating when running cat and have also checked the AN8250N on the floppy pcb and it appears to respond correctly on the signal pins as far as can tell from the probe.  I didn't check the voltages going to the actual motor, looking at the data sheet from the AN8250N I'm not sure I can test that with the equipment I've got other than to check the resistance between the pins.


However what I have found is that the stepper motor is showing signs that it is trying to move so now I'm suspecting that the stepper is actually jammed - I have uploaded this video to youtube to show what is happening.  https://www.youtube.com/watch?v=2QDcFbfdB6c


I can find some useful post from Bryce where he took apart a stepper motor and repaired it, what isn't clear is whether this was the same kind of failure and wether what I'm seeing is a jammed stepper or something else.
Cheers Trevor 
Title: Re: Fixing Floppy-Drives
Post by: tjohnson on 02:47, 03 May 17

Little bit more tinkering and almost there.  I rotated the shaft a few times and now its moving, hopefully just needed a bit of encouragement to get it going again.  I'm feeling a bit happier about this now!


I've now got it reading discs however it is not quite right yet, for example on the game Tomahawk it will load the loading screen but then keeps tracking to the same spot over and over.  I've had a bad read error.  I'm now hoping this is a process of calibration which I'm hoping that Bryce can tell me how to calibrate.


Right now time for bed, it is way to late to be tinkering with my childhood computer on a school night.
Title: Re: Fixing Floppy-Drives
Post by: Bryce on 12:05, 03 May 17
You may just need to give the motor some time to come back, it may still be sticking at some points and need some more lubrication. The drive where I needed to fix the stepper motor had a broken bushing. If yours had the same problem it wouldn't be reading disks at all.

Bryce.
Title: Re: Fixing Floppy-Drives
Post by: tjohnson on 13:15, 03 May 17
Cheers Bryce. I couldn't resist as further test this morning and seemed to have improved overnight and fully loaded the test disk but looked like it stuck a couple of times.   Maybe a bit of use will loosen it up.  Is there anyway lube the internals a bit as it sounds a little squeaky when moving by hand?

Sent from my E5823 using Tapatalk

Title: Re: Fixing Floppy-Drives
Post by: Bryce on 13:22, 03 May 17
Not really. The problem is, if you remove or even loosen the stepper motor the entire drive will need to be recalibrated.

Bryce.
Title: Re: Fixing Floppy-Drives
Post by: Audronic on 02:50, 04 May 17
@tjohnson (http://www.cpcwiki.eu/forum/index.php?action=profile;u=2129)

You could put a small drop of sewing machine oil at the both bearing ends (On the bearings)

Ray
Title: Re: Fixing Floppy-Drives
Post by: tjohnson on 13:50, 04 May 17
Cheers, will give that a go.  The drive doesn't seem too bad, I tried a number of disks and couple got read errors that may be the disk more than the drive.   Want to try and get some diagnostic programs on there to check rotation speed so I need to expedite my 3.5"  connection to do so.
Cheers Trevor

Sent from my E5823 using Tapatalk

Title: Re: Fixing Floppy-Drives
Post by: tjohnson on 11:11, 21 May 17
So I thought I'd update this on the latest on returning my disk drive back to working order.  I found the drive very temperamental and definitely wasn't working right seemingly have read errors on the majority of the disks I have, that just couldn't be right.  I managed to measure the rotation speed and it was pretty much spot on 300rpm so that didn't appear to be the issue.  The head was cleaned but what I noticed was the little felt pad on the spring arm was worn and out of shape, not flat.  I pulled what was left off and glued some replacement material on -a couple of small bits of cleaning glass lense cloth.  I also marked the stepper motor and released the screws so I could do some calibration and know generally where I started.  Anyway the final upshot is now that it reads disks it couldn't before and seems to be fully working again, finally.  It has taken me a lot of time messing around but I'm pleased the original drive is now working correctly again.  I think the main issue was the felt pad, I guess that helps to apply pressure to ensure the disk surface is flat to the read head but with it out of shape the pressure would have been off.
Title: Re: Fixing Floppy-Drives
Post by: llopis on 20:50, 06 January 19
I have a question about a floppy drive issue I'm having on a 6128, so I thought maybe keeping it in this topic would be a good idea:


When I do CAT, the drive spins up but it returns "Disc Missing" (I don't hear any seeking of the head).
- I replaced the belt.
- Solder joints looked just fine (it's a newer drive model, probably from 88 or 89).
- A different drive DOESN'T in that CPC and that drive works on a different CPC.
- There's connectivity in the ribbon cable from the PCB to the end of the cable.
- I took out the 16KB ROM (which I believe it's the one that holds the floppy disk controller logic) and read it back, and it seems to be correct.

This is where it gets pretty new to me since I've never had to deal with the FDC directly. What can I test to make sure the FDC is working (or not)? I looked at the output of pin 37 with a scope and I don't see any activity when I do a CAT (or press R to retry). The Ready signal is obviously never high either. Is there a better test I can do? Or is it safe to unsolder it and put a different FCD there?

Edit: I looked at the activity of pin 37 on a working 6128 and there are some pulses during a CAT operation. Also, pin 36 (Head Load) isn't used in the CPC from what I can see in the schematic, but there's plenty of activity there in a working 6128, but it's low on the one that doesn't work. So that's making me think it's the FDC.

Thanks.
Title: Re: Fixing Floppy-Drives
Post by: Audronic on 01:10, 07 January 19
@llopis (http://www.cpcwiki.eu/forum/index.php?action=profile;u=1728)


In general terms I would be looking at the Buffers IC202, IC203, IC204 First as these talk to the outside world
and are prone to Glitches.


Just a thought


Good luck


Ray
Title: Re: Fixing Floppy-Drives
Post by: Bryce on 10:33, 07 January 19
@llopis (http://www.cpcwiki.eu/forum/index.php?action=profile;u=1728)


In general terms I would be looking at the Buffers IC202, IC203, IC204 First as these talk to the outside world
and are prone to Glitches.


Just a thought


Good luck


Ray

If a different drive works on that CPC, then all the buffers are fine. I'd check what speed the disk is turning at. It maybe be on the border of being too fast or too slow and the tolerances of the other CPC (where it works) are a bit wider.

Bryce.
Title: Re: Fixing Floppy-Drives
Post by: llopis on 11:30, 07 January 19
If a different drive works on that CPC, then all the buffers are fine. I'd check what speed the disk is turning at. It maybe be on the border of being too fast or too slow and the tolerances of the other CPC (where it works) are a bit wider.
Oops, bad typo on my part, sorry. A working drive does NOT work on that CPC. And the drive that I'm having issues with WORKS on a different CPC. Yeah, I know, that changes everything.


So it's clearly not the drive, but the CPC board. Do you think the FDC is the likely culprit, or could bad buffers be shorting the signals? I suppose I could start de-soldering and socketing and swapping ICs...
Title: Re: Fixing Floppy-Drives
Post by: Bryce on 11:35, 07 January 19
Ok, if that's the case, then I'd definitely take a look at the buffer chips. However, not the IC's Audronic mentioned, the output buffer (IC206) is the most likely culprit.

Bryce.
Title: Re: Fixing Floppy-Drives
Post by: Audronic on 11:41, 07 January 19
@llopis (http://www.cpcwiki.eu/forum/index.php?action=profile;u=1728)


I was referring to this Schematic


Ray
Title: Re: Fixing Floppy-Drives
Post by: llopis on 12:05, 07 January 19
I was referring to this Schematic
What version of the schematic is that, Ray? It looks different from my schematic (and my board layout):


In any case, we're all taking about the same ICs. Any suggestions on how to test them? Pull them out and feed the gates and check results?
Title: Re: Fixing Floppy-Drives
Post by: Bryce on 12:14, 07 January 19
I haven't seen that schematic version either, I don't think? Is it from the ammendment?
You can check any of the outputs such as MOTORON or STEP and check that these are going low when they should.

Bryce.
Title: Re: Fixing Floppy-Drives
Post by: llopis on 15:12, 07 January 19
I haven't seen that schematic version either, I don't think? Is it from the ammendment?
You can check any of the outputs such as MOTORON or STEP and check that these are going low when they should.
Yeah, I just saw that schematic in the ammendment. The weird things is... my connections aren't exactly like either schematic! In mine, they're more like the original service manual, but pins 37 and 39 of the FDC are hooked directly to IC208 without first going through IC205. Anyway, I'm investigating as I type this.


Also, I went ahead and swapped the FDC (having a good desoldering gun is sooooo handy) and, as you both predicted, that wasn't it. So it has to be one of the buffers...
Title: Re: Fixing Floppy-Drives
Post by: Bryce on 16:55, 07 January 19
I could have told you that it's not the FDC, but de-soldering practise is always good :)

Bryce.
Title: Re: Fixing Floppy-Drives
Post by: llopis on 00:08, 08 January 19
I replaced IC208 (a quad NAND gate) since that's where the STEP signals were going, but it made no difference.


At this point, I think I need to gain a good understanding of the communication protocol between the FDC and the floppy drive. Does someone have a good document that goes over the protocol? The uPD765A datasheet goes over a lot of that, but it's too much detail for me right now. I'd love to see some example state diagrams for simple operations on the CPC (or in general).
Title: Re: Fixing Floppy-Drives
Post by: llopis on 12:53, 08 January 19
New development: I tried that CPC with an external USB floppy drive emulator and it works fine. Unless the emulator is much less strict about some potential signals being incorrect, I think that means that the problem lies in the cable connecting the original drive, right? I tested for continuity from one end of the cable to the other, but maybe some contacts on the PCB aren't good enough. I'll continue investigating...
Title: Re: Fixing Floppy-Drives
Post by: Bryce on 13:21, 08 January 19
The only signal not shared by the internal and external drives is drive select (NDSEL and NDSEL1), controlled by IC202 (according to Audronics schematic notation). Check that this signal (Pin 10 of the 26pin connector) is definitely going low during disk access.


Bryce.
 
Title: Re: Fixing Floppy-Drives
Post by: tjohnson on 15:41, 08 January 19
I looked at ndsel1 on a scope and generally found it was high but goes low upon accessing the drive, so even with b drive selected the signal will remain high until the computer accesses the drive. It always looked high on my cheap multimeter.
Title: Re: Fixing Floppy-Drives
Post by: Bryce on 15:43, 08 January 19
NDSEL1 is for the B drive. What's NDSEL doing?

Bryce.
Title: Re: Fixing Floppy-Drives
Post by: llopis on 17:02, 08 January 19
The only signal not shared by the internal and external drives is drive select (NDSEL and NDSEL1), controlled by IC202 (according to Audronics schematic notation). Check that this signal (Pin 10 of the 26pin connector) is definitely going low during disk access.
NDSEL is permanently high for me. But looking at the origin of the signal, it's the negative of pin 38 (which is always low for me). Pin 38 is:
Quote

38. LCT/DlR (Low Current/Direction)
In the read/write mode, the LCT output indicates that the R/W head is positioned at cylinder 42 or greater. In the seek mode, the DIR output determines the direction the head will move in when it receives a step pulse. If DIR is 0, seeks are performed in the outward direction; DIR is 1, seeks are performed in the inward direction.
Why would they use the negative of that to select the drive? I'm not understanding something.

Title: Re: Fixing Floppy-Drives
Post by: tjohnson on 23:39, 08 January 19
NDSEL is permanently high for me.



Sorry my post earlier was really to say depending on how you are measuring it, it may always appear high to you, i.e. if you measure it with multimeter, that was my experience anyway.
Title: Re: Fixing Floppy-Drives
Post by: llopis on 23:50, 08 January 19
I looked at the drive select signals and the ones that make more sense are NDSEL0 and NDSEL1 (I think NDSEL must be a mistake in the label and it should be NDDIR or something like that).


NDSEL0 and NDSEL1 make a lot of sense because they're negatives of each other, and they're generated from the FDD pin 29 (US1):
Quote

US0 US1(UnitSelect0,1)
The US0 and US1 outputs select up to 4 floppy disk drive units using an external decoder.


Surprisingly, during the idle state (the drive not even spinning), US1 is high most of the time with pulses to 0 at periodic intervals. I wonder what that's about (this is on a working CPC). When the drive is accessed with a CAT, US1 will go low for some time (see screenshot).


On the non-working CPC, US1 never changes from the high with pulses to 0 (this is measured directly at the FDD).


I changed the drive cable just for the heck of it without any real hope of change, and of course there's no change.


Summary:

So something it's preventing the FDD from working correctly (with unit A), but it's not the FDD itself. I'm pretty baffled!

Any thoughts on what else I can test?
Title: Re: Fixing Floppy-Drives
Post by: Audronic on 00:18, 09 January 19
Just some thoughts

AT Pin  29 Of the Z765APS This line should toggle as it selects the drives.

At Pin 3 (output) of the 74LS38 (IC202) this should be LOW to select Drive 1 (ONE)
And at the collector of the Q201 KTC1815 this should be LOW to select Drive 0 (ZERO)

The 74LS38 is OPEN COLLECTOR Must have a pullup somewhere

The last thing is to check the Resistors R201 and R202.

Ray
Title: Re: Fixing Floppy-Drives
Post by: tjohnson on 00:26, 09 January 19
Is this an internal 3" drive you are having issues with?  Did you say a floppy drive emulator (gotek?) works when connected to the edge connector of the computer?
Title: Re: Fixing Floppy-Drives
Post by: llopis on 09:39, 09 January 19
Thanks, Ray. I'll check those today, although my layout is definitely not like the one from the revised manual--it's much closer to the original manual, which doesn't have a transistor there and instead feeds NDSEL1 back through another NAND gate along with some fixed voltage (I assume to avoid hitting fanout requirements). But the idea is similar.

Is this an internal 3" drive you are having issues with?  Did you say a floppy drive emulator (gotek?) works when connected to the edge connector of the computer?


Correct. A stock 3" drive (which works in other computers).


The drive that I tried on the edge connector is Pyotr's USB emulator, but I believe it's very similar to a Gotek. I might try a Gotek as well just to be extra sure.
Title: Re: Fixing Floppy-Drives
Post by: Bryce on 10:03, 09 January 19

On the non-working CPC, US1 never changes from the high with pulses to 0 (this is measured directly at the FDD).

Any thoughts on what else I can test?

If US1 is never going low, then that's your problem. Either the inverter isn't working / stuck high, or the 765 isn't. You need to trace where that issue is originating.

Bryce.
Title: Re: Fixing Floppy-Drives
Post by: llopis on 10:41, 09 January 19
If US1 is never going low, then that's your problem. Either the inverter isn't working / stuck high, or the 765 isn't. You need to trace where that issue is originating.
But that's the thing: The 765 is working fine (tested on another computer) and the inverter is down the line from it (and I see it inverting the pulses correctly). So there's something else that's preventing the 765 from working correctly.
It's not a bad ROM (replaced and tested). I thought it could maybe be the data lines going to the FDD, but then I can't explain why it's working with the external drive. This is quite the mystery...
What's the role of the SED9420? It seems to be involved in the floppy disk control somehow. I think it's listed in the schematic as FDC9216, which I imagine is the same. Could that be causing this problem?
Title: Re: Fixing Floppy-Drives
Post by: Bryce on 10:44, 09 January 19
The SED is a data separator. It sort of cleans up the signals coming from the disk. If it wasn't working, the external drive wouldn't work either.

Bryce.
Title: Re: Fixing Floppy-Drives
Post by: Audronic on 13:33, 09 January 19
@llopis (http://www.cpcwiki.eu/forum/index.php?action=profile;u=1728)


I have had a look at your Schematic

And here are some thoughts

The voltages at rest should be :-

IC206    74LS38.    Is it a 74LS38 ?

Using a CRO or VoltMeter

Pins 9 and 10  + 4.1 Volts.  Pin 8  + 0.2 Volts
Pins 4 and 5    + 0.2 Volts.  Pin 6  + 4.8 Volts

Monitor Pin 6 ONLY and do a Cat it should at some stage toggle LOW to + 0.2 Volts.

If not then Monitor pin 8 and repeat the test. It should go from + 0.2 Volts to +4.8 Volts.

Any of the above don’t  change then :-  Change the IC206

Ray

Title: Re: Fixing Floppy-Drives
Post by: llopis on 13:53, 09 January 19
The voltages at rest should be :-

IC206    74LS38.    Is it a 74LS38 ?

Using a CRO or VoltMeter

Pins 9 and 10  + 4.1 Volts.  Pin 8  + 0.2 Volts
Pins 4 and 5    + 0.2 Volts.  Pin 6  + 4.8 Volts

Monitor Pin 6 ONLY and do a Cat it should at some stage toggle LOW to + 0.2 Volts.

If not then Monitor pin 8 and repeat the test. It should go from + 0.2 Volts to +4.8 Volts.

Any of the above don’t  change then :-  Change the IC206
IC206 is indeed a 7438 (quad NAND gate) and I haven't changed it yet.
But, pins 9 and 10 are tied to pin 29 in the FDD, which is US1. I put up a screenshot of that signal a few posts ago (it averages out to be around 4V since it's high with some pulses to 0).


I can confirm that pin 8 is correctly the opposite of that, and that pin 6 is similar to US1 (the negative of pin 8 again).


But when I do CAT, US1 (and any of the other pins) never change like they do on a working CPC. And because there's activity on those pins, it's also clear that they're not just shorted to 0 or 5V. That's what makes this so weird.
Title: Re: Fixing Floppy-Drives
Post by: Bryce on 14:00, 09 January 19
It could still be IC206. There's a difference between a signal going high/low on a scope and actually being able to drive a gate it's connected to. I'd change IC206 anyway before looking further.

Bryce.
Title: Re: Fixing Floppy-Drives
Post by: llopis on 14:03, 09 January 19
It could still be IC206. There's a difference between a signal going high/low on a scope and actually being able to drive a gate it's connected to. I'd change IC206 anyway before looking further.
I'll try it because there isn't much else I can think at the moment (and I have a spare one from another CPC), but remember that the FDD IC isn't even setting the signal to a stable low to start with during a CAT operation.
Title: Re: Fixing Floppy-Drives
Post by: llopis on 14:41, 09 January 19
I just learnt something new I didn't know. Putting it here to share with others. Remember how I was a bit puzzled by the high US0/US1 lines with periodic pulses to 0V? It turns out the FDD is polling to see if there are disks on the different drives every ms.


Quote
After reset has been sent to the µPD765A/µPD765, the unit select Lines US0 and US1 will automatically go into a polling mode. In between commands (and between step pulses in the seek command) the µPD765A/µPD765 polls all four FDDs looking for a change in the Ready Line from any of the drives. If the Ready line changes state (usually due to a door opening or closing) then the µPD765A/µPD765 will generate an interrupt. When Status Register 0 (ST0) is read (after Sense Interrupt Status is issued), Not Ready (NR) will be indicated. The polling of the Ready line by the µPD765A/µPD765 continues continously between commands thus notifying tthe processor which drives are on or off line. Each drive is polled every 1.024ms except during the Read/Write commands. When used with a 4MHz clock for interfacing to minifloppies, the polling rate is 2.048ms.


And this reminds me of one more thing: This CPC, unlike any others I know, when I turn it on, I hear slight noise in the floppy drive. Like it's doing one tiny step or moving the head ever so slightly. It happens every time I turn it on.
Title: Re: Fixing Floppy-Drives
Post by: llopis on 23:16, 09 January 19
OK, this gets crazier! (but it's a new data point, so I'm hopeful).


Before I had tried Pyotr's USB floppy disk emulator on the edge connector. Now I decided to try a regular Gotek. It also worked.


But... I decided to check out drive A while I had the Gotek connected and... it worked!!!


So I started eliminating things:
- The Gotek could have the disk removed and it worked
- The Gotek could be unpowered and it worked


And this is what I came up with: As long as the Gotek cable is plugged into the edge connector, it works.  :o :o


It's a ribbon cable with a couple of switches. The one on the left sets the Gotek to be drive A or B (I imagine it commutes the NSEL1 and NSEL2 signals). This only works if it's in the "B drive" setting (meaning, the Gotek is the B drive, so supposedly not changing the signals around). The switch on the right it's an "external head drive selection switch". I don't think that one matters which setting it's on.


One more piece of data: If while I have the Gotek cable connected, I remove the 3" disk, and I do a CAT, the computer hangs there forever.


It's as if the FDD isn't detecting that the disk is in, and with the Gotek cable (somehow) it's forced to think it's in (even if it's not).


Does this make any sense to anyone?
Title: Re: Fixing Floppy-Drives
Post by: llopis on 23:34, 09 January 19
I think I might have figured it out!!!


That cable has two connectors tied together: pins 1 and 2. That's the READY signal tied to GRND. Which gets flipped by an inverted and passed as ready to the FDD.


For drive A, the ready pin is 26, which is supposed to be connected to pin 1 on the edge connector and... it's not! I don't see a visual break (and I even desoldered the cable and cleaned up that area yesterday), but there's definitely no connectivity. I'm about to add a bridge and keep my fingers crossed.


To be continued...
Title: Re: Fixing Floppy-Drives
Post by: llopis on 23:42, 09 January 19
That was it!!! Wow! That was an intense repair! This is actually why repairing computers is so much fun  ;D For every 10 boring RAM-burned-out repairs, you get an challenging case like this one.