Grrr! 6128 drive still not reading disks after belt change

[MugUK]

I've taken the machine apart, taken the drive mechanism apart and replaced the drive belt. 

This seemed to be OK, even if Amstrad designed this device to be 'fat fingers non-compatible'!

I connected it all back up and I'm still getting the same problem.  It won't read the disk.  The LED comes on but no life seems to come from the drive at all.

I've taken the drive out a few more times to double-check I reconnected everything and compared notes against:

   
• this Wiki
• this guide (How to dismantle a CPC 6128 and replace the drivebelt)
• this page (Servicing the Amstrad CPC6128 Disk Drive) and
• this page (Retro-Zone.Org - Project - Change Drive Belt on an Amstrad CPC 6128). 

I've got a Z70312 model drive.  Which wasn't listed on the retro-zone website and, on my first attempt, was a real pain in the rear end to get the board lifted high enough so I could get the belt on via some tweezers.

I can't see what I've done wrong

Is that I've more than likely got a duff drive and I'm better off buying a replacement one?  Or is there something else I can check?

Or should I send it off to the repair place on eBay that will guarantee a working drive or I get my money back if it's a total duffer?

It's annoying because there's so many disks lying around that I'd like to take a look at 

[Bryce]

Is the disc turning at all? Is the drive getting 12V ?

Bryce.

[MugUK]

The LED comes on but there just doesn't seem to be any life in it. 

[Bryce]

The LED is being lit by the 5V supply that supplies all the electronics, but the motors are powered by the 12V supply. I suspect the drive isn't getting 12V.

Bryce.

[MugUK]

The LED is being lit by the 5V supply that supplies all the electronics, but the motors are powered by the 12V supply. I suspect the drive isn't getting 12V.

Bryce.

Ah right .. I'll take it with me down to the Retro Computer Museum guys next weekend and see what they can say.  Me & hardware fixing aren't very compatible

[steve]

Is your monitor a CTM 640, CTM 644 or are you using an "external" power supply?

[MacDeath]

One big issue may just be the disk who don't take the 20 years of inactivity well... faulty disk simply...

Seriously, the disks age not as well as the disk driver, being the magnetized piece of scrap they are...

[Spirantho]

I had a drive that did this too. It wasn't spinning.
Three things were wrong:
* The connection was loose to the drive. Just a dodgy wire.
* There's a two pin black oblong which looks like a kind of squared-off transistor. This is actually a fuse. If it blows (which probably won't show) then your drive gets no 12V.
* There was another similar looking transistor on the board linked to the fuse which had gone (and probably what blew the fuse). When I put the parts in from another drive, it worked perfectly.

[MugUK]

Is your monitor a CTM 640, CTM 644 or are you using an "external" power supply?

I think it's the CTM644 - whichever one that has got the 12v connector underneath the display    (it's upstairs and I'm downstairs writing this!)

One big issue may just be the disk who don't take the 20 years of inactivity well... faulty disk simply...

Seriously, the disks age not as well as the disk driver, being the magnetized piece of scrap they are...

This is a possibility.  It was sold as seen.  Just sod's law that both Amstrads I've bought are not working in one way or another.

I had a drive that did this too. It wasn't spinning.
Three things were wrong:
* The connection was loose to the drive. Just a dodgy wire.
* There's a two pin black oblong which looks like a kind of squared-off transistor. This is actually a fuse. If it blows (which probably won't show) then your drive gets no 12V.
* There was another similar looking transistor on the board linked to the fuse which had gone (and probably what blew the fuse). When I put the parts in from another drive, it worked perfectly.

That's why I'll let one of the more technical people at the Retro Computer Museum take a look at it next weekend as there's a big event on @ Snibston Discovery Centre (which I'm helping out at).  They've got a 6128 with a HXC inside it which makes it easier for visitors to select games etc.  So hopefully I can get it looked at there.

[MugUK]

An update. The good news is that the 6128 drive powers up and CATs any disk put in there which points to my monitor being the culprit re: 12v power not working.

The bad news is that no game or utility loaded from disk will run. Every RUN "xyz attempt causes it to return to the prompt.

So after the others took a look at it after all the other machines were set up, the general concensus was that there's a problem with one of the RAM chips as everything else seems to work.

Any suggestions? Or do I go looking for a third Amstrad?

[Bryce]

Definitely a RAM issue, start swapping the ICs.

Bryce.

[00WReX]

Hi Bryce,
With the RAM chips, have you had any luck or is it a worthwhile exercise when trying to find a faulty RAM chip to attempt to piggyback the chip wth a known worker prior to any removal to attempt to isolate the faulty one.

Considering there are 16 RAM chips in the 6128 and potentially only 1 is faulty.

For the average person with average or below soldering skills, removing RAM chips is not that easy.

I did read some people suggesting this on some C64 forums when chasing faulty RAM...simply get a spare RAM chip then basically wedge it ontop of and existing RAM chip so that all the pins contact the existing chips pins.

Not always going to work depending on how the chip has died, but as an initial exercise that may help track down an individual faulty chip.
What are your thoughts on the validity or effectiveness of doing this ?

I think for most people unsoldering the old and then soldering in NEW chips would be a nightmare, with the possibilty of going through all the RAM chips to find that the 16th/last one is the dead one...


Cheers,
Shane

[MugUK]

Soldering is not something I would know where to start with so it looks like I need to hunt for another 6128.

[Bryce]

Some people go through each RAM by piggy-backing each one with a good RAM, but to be honest, I'm far too lazy for all that shite, especially when RAM ICs aren't all that rare or expensive. I usually rip out all 8 or 16 of them and install sockets and new RAM. that way I know that it works again and that all RAMs are new.

Bryce.

[MugUK]

The 6128 was left with one of the locals who will get their sledgehammer tools out and have a look at it for me. I'm back there next month so I hope that someone will have the time to take a look at it.

[Gryzor]

Good luck with it mate...

[MugUK]

Just received a lovely text message from Andy who runs the Retro Computer Museum.... my 6128 has been fixed.  The duff memory chips have been replaced and the drive replaced because my handiwork wasn't good enough by the sounds of it.

I picked up a 3.5" adapter at their event over the Easter Weekend and will be picking my working 6128 at the next event in May.  Just got to get one of those 6128 TV adapters as the 12V from my monitor is duff (and a cheap slimline telly to plug it into).

I can then (finally!) have a proper play and start wading through all those disks.

[beaker]

Just got to get one of those 6128 TV adapters as the 12V from my monitor is duff (and a cheap slimline telly to plug it into).

Hey MugUK - glad you and your friend managed to resurrect the 6128.

I assume you're talking about the MP2?

Could you not use another 12 volt supply from somewhere like Maplin? Apparently the tip is negative on that lead from the 6128.


Alternatively, I also just bought an original 6128 (fortunately it was only the drive belt that needed changing on mine) without the monitor and then bought the scart and power supplies from retro computer shack which works great on my plasma, although it sounds like it may need some modification with some TV's to get RGB (I can force RGB on mine although it annoying shares the same input as HDMI - thanks Pioneer  ).

It costs 2 1/2 times what you paid for the machine but thought I should mention it as it will produce a better image than the MP2 (although I've never owned one).

power and leads

[MugUK]

Just seen pictures of it up and running on the RCM forum

The reason for the power leads + SCART etc. is that I have the one 19" TV/VGA combo that I prefer to use for my retro machines.  Means that there's only one machine unpacked and ready to use and not cluttering up space with more monitors etc.

So in less than a few weeks, I'll finally be able to play the game I did the graphics conversion for. I've been waiting 25 years but it'd be worth it

[beaker]

Ah, I see it was that same kit you ordered before I mentioned it and not an MP2 lol    Good choice! 12V power supply could be a bit longer as the box is dangling behind my desk but there's no weight to it so I am not too worried.

Hope you don't mind if I add the link to your post on this forum?
http://retrocomputermuseum.co.uk/forum/index.php?PHPSESSID=2e2coe9hq20siq18kbs7invrc1&topic=4446.msg45464#new

Looks like a nice clean machine 

I hope the 25 year wait will be worth it, good luck 

[MugUK]

I ordered the tape adapter and replacement drive belt(s) from the same eBayer so I know their stuff is good

No probs on the link .. I plug CPC Wiki forum (amongst others) on my signature on RCM

[Gryzor]

Yeah! Free advertising! A link would work better though


J/K. Really glad you got it sorted out. Too bad you'll have to wait, hope your enthusiasm doesn't fail till then!

[MugUK]

Yeah! Free advertising! A link would work better though

I'm one of the admins and RCM has just got official charity status so it's all looking up

As for the link, there's not enough room in the signature space for all the HTML links for all the forums *and* my 360 tag

J/K. Really glad you got it sorted out. Too bad you'll have to wait, hope your enthusiasm doesn't fail till then!

I've got 80+ discs to look through *and* a dual-layer DVD full of stuff inc. disk images to wade through after that

[Bryce]

If the GT65 is supplying 5V, then it should be very easy to fix the 12V supply. The 5V output is derived from the 12V supply, so there are only one or two (cheap and easy to source) parts in the monitor that could be defective. Actually it's most likely a bad/dry joint, because I doubt those parts would fail, even if someone had shorted the 12V output. It's probably worth investigating further.

Bryce.

[Bryce]

Here's the schematic for the GT65 12V output. The voltage at "A" must be there, otherwise you wouldn't have 5V either. So either there's a dry joint on one of these points starting from the connector. That's only 9 possible points you need to check. If they are ok, then the 7812 is destroyed and needs to be replaced. The 7812 cost a whole 28 Cents. The capacitor may be damaged too, but the output would still work, even if this was damaged. Either way it cost about 8 Cents and you may as well swap it too.

Bryce.