Author Topic: Amstrad 6128 plus CPC 6128 plus does not start  (Read 3795 times)

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Offline flufduff

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Amstrad 6128 plus CPC 6128 plus does not start
« on: 01:45, 30 October 14 »
Hi folks.

I'm new to this forum - and have been quite happy to see all the information on this site. A CPC464 was my first computer about ... 30?! years ago.
I have considered for some time to get a 6128 plus now, for I wanted one with a built in disk, and also sprites support etc. Now, I finally found one that I could collect in person :-)

Bad news: It doesn't boot from its ROM. And I was wondering, whether anyone here could tell from its behaviour, whether the problem might be in the ROM cartridge (i.e.: easily curable), or in the large onboard ASIC (i.e.: non curable), or something in between (i.e.: curable, with some work).

Details:

Well, it didn't look too clean from outside. After wiping a layer of dirt off, I thought I'd better look inside - and found the leftovers of numerous bugs (think: hundreds). All these parts wouldn't stick to the printed circuit boards so much, but to the bottom plastic, to the horizontal metal layers of the disk drive etc. (Somewhat disgusting, sorry.) I didn't make a notice in the machine logbook, but gave the machine some emergency cleaning. The floppy belt is also unusable, but I expected that and I don't mind.

The machine came with the burning rubber / locomotive basic ROM.

I've made a CPC 6128 Plus to SCART cable and connected it to an Amiga monitor. Signal injection from Multimeter to the Audio L and Audio R pins on the CPC end makes the monitor emit the beep, and Signal injection from Multimeter to the R, G, B pins makes coloured stuff appear on the monitor - and switching the computer on (supplied with 5 Volts from a laboratory power supply that does *not* reach its current limitation) makes the black monitor image change into a black image with a very light regular scanline/retrace pattern, and also a very high pitched just audible beep comes from the monitor (most of the time, i.e. when the machine appears to start in some way).

Ah, and the power light is on, of course.

Also, when this change in black screen and audible audio occurs, the multimeter shows some 100 kHz up to 4 MHz at the Pins of several ICs, including the CPU, and the ROM socket. So I'm relatively sure, that the CPU runs (in some way), but the machine either fails to initialize the video IC (or program some other internal registers) completely, or the ROM has a problem, or ... something in between.

Now my actual question: Has anybody seen the same behaviour already?

May I just get another ROM cartridge, and hope it would start then?

Or is this a typical behaviour after the internal big Amstrad-ASIC has been killed, which I probably can't replace (it's large, custom, SMD...).

I can do further diagnostics to quite some level, I can also find defective 74xx ICs etc. - but before I start out doing that work, I thought I'd rather ask. (And it may be months or years before I find the time to do it).

Another question (the scanned user manual available somewhere was not too detailed here due to missing images): I read somewhere that the built in floppy drive might live w/o an extra 12 V power supply. I also found in the service manual what looks like a weird construction, where some second 7405 relative is put on top of the 5V line of another one, to derive some 10 V distance in total. Well, I've not looked there in detail and might shake my head in wonders when I do (about the BWLers vs. engineers thing) - but until then: could you tell me if it's really true that the machine needs only one 5 V input?

Ok. I say thank you to all of you for reading this, and thanks in advance for any response.

Kindest regards - flufduff :-)
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Offline flufduff

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Re: Amstrad 6128 plus CPC 6128 plus does not start
« Reply #1 on: 02:19, 30 October 14 »
 :) :) :)


Hello all again :-)

Given I'm still curious, I thought I'd try it again - after all the machine had two days or so to dry, just in case there should be some water left.

It produced the same results. And I forgot to mention: Same dark screen image with or without ROM cartridge inserted.

So... I opened the cartridge, found it basically good looking (no bugs there), but just possibly a bit of damp on two leads. i cleaned all the leads quickly/coarsely with a screwdriver, inserted the ROM PCB, gave it a new cup of tea - no, I mean, switched it on, and - flups - really...? - as I've been used to so often, the very faint sound of a CPC booting, now from the monitor, blue and yellow, and while I was still looking in astonishment and happiness - the cartridge game, sound and colours nice and bright & sharp :-)

All perfect now. And yes, it was the ROM cartridge - or the contacts in the ROM slot, maybe.

One more Amstrad CPC 6128 plus revived. :-) :-) :-) :-)  :-) :-) :-) :-)  :-) :-) :-) :-)  :-) :-) :-) :-)  :-) :-) :-) :-)  :-) :-) :-) :-)

Still thanks for looking and kind regards! flufduff. (& Good Night :-)  )



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Offline CraigsBar

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Re: Amstrad 6128 plus CPC 6128 plus does not start
« Reply #2 on: 02:23, 30 October 14 »
So glad you got it working. Now that's one more person for the we need new carts camp.

Welcome.
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Offline Morri

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Re: Amstrad 6128 plus CPC 6128 plus does not start
« Reply #3 on: 02:56, 30 October 14 »
Hi Flufduff and welcome to the forum. I hope using your new plus brings you the same joy as it did 30 years ago. There is alot to catch up on.  ;D
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Keeping it Kiwi since 1977

Offline Bryce

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Re: Amstrad 6128 plus CPC 6128 plus does not start
« Reply #4 on: 11:04, 30 October 14 »
Hi Flufduff,
     congrats on getting it working. It was most likely dirt on the cartridge edge connector. Just to answer your other question. Yes, the CPC+ is a pure 5V design including the floppy drive. No 12V or anything else needed. Not sure what you mean with the second 7405 (Did you mean 7805?). If you mean the schematic below (which is in the Plus Service Manual), this is just for the GX4000. The 11V input is to supply the correct switching voltage to the SCART output. The second 7805 is so that the video circuitry has a completely isolated 5V supply to avoid noise in the picture.

Bryce.



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Offline flufduff

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Re: Amstrad 6128 plus CPC 6128 plus does not start
« Reply #5 on: 00:15, 31 October 14 »
Hi Bryce, Morri and Craigsbar!

Thanks a lot for your quick and kind replies. Craigsbar, yes, that's been the schematic that I had briefly seen, and of course I meant 7805, I've just been too tired yesterday.
And your explanation has been very helpful to ease my wondering and disbelief. :-)

-

Actually, the machine boots quite reliably now. If not, a little reseating of the ROM does help. And yes, I'm quite happy.

Yesterday (after the second post) still was a bit troublesome: When I went into BASIC the first time, it would show random keystrokes, apparently also from the Joystick. So I thought I might have got the error that was mentioned in other posts on this site... but then, I decided to look between the keyboard films - because I had really had everything in the shower, with soap, due to the insect invasion. I found that water had got in between, so I opened them up, dried them, and thereafter the random keystrokes were gone. :-) :-) I had overlooked the water when first reviewing the keyboard after the cleanse.

The other thing is, it has a flaky f1 key. Apparently, asking to press f1 just after startup, took its toll. If I find it sufficiently annoying, I will try to fix this - about 2 decades ago, I had a laptop whose keyboard films went bad notoriously and got some practicing on this with a pencil and silver paint...

Finally... Hmpf, it has a French keyboard. Naturally, because I picked it up there. But whoever designed that must have been in ... a different state of mind, I guess. :-)
I know that I can reprogram the keyboard, or get another ROM, or possibly download and burn one or so. But not now.

I've typed in a few little BASIC programs already, playing around with colors and sound - just nonsense - and knowingly without a means to save later on. But merely switching the inks gave the same feelings back to me that I remember I had when doing so these many years ago. I even remembered some of the colors I had prefered back then, like 15 for orange on black in mode 2 etc. I felt it's quite astounding how exactly such ... emotions? impressions? perceptions? ... can be reproduced by a certain sight / impression (it includes the timing, the computing noise in the speaker, the screen updates, of course), after so many years. ... And even though it's so way behind anything a modern machine can do - it still makes it clear, that it is a *generic* toy, i.e. it's not completely defined or restricted so much in advance as to what it can do - and it lives on it's user's phantasy - and this can be seen from the first little programs. Or when you type cat and the floppy motor starts running - as a placeholder for any one action in the "real" mechanical world triggered merely by some program stuff.

Ok. Semiphilosophic mode off. :-)

-

Now, I will probably fix the drive, add a tape port (adding cables...), and get the old homecomputer software case here or get the new machine there some time.
It will take me a lot of time to do that, however - cause I don't come near the software soon. And if I do, I actually don't know whether I would want to take it, cause it's in a house, with people, that belong to the time where it came from (with the cpc 464 by the way, too), and I've got a strange feeling considering taking that setting apart (again). - Will see.

-

Thats as much as I can write now. - I also wish you a lot of joy with your machines - it's astounding (looking around on ebay) how currently the interest in homecomputers from back then seems to return in so many people at the same time...

Kind regards again, Fluffduff
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Offline Bryce

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Re: Amstrad 6128 plus CPC 6128 plus does not start
« Reply #6 on: 00:28, 31 October 14 »
Does the drive spin / LED go on? Or is it completely dead?

Bryce.
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Offline CraigsBar

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Re: Amstrad 6128 plus CPC 6128 plus does not start
« Reply #7 on: 00:54, 31 October 14 »
Now, I will probably fix the drive, add a tape port (adding cables...), and get the old homecomputer software case here or get the new machine there some time.
It will take me a lot of time to do that, however - cause I don't come near the software soon. And if I do, I actually don't know whether I would want to take it, cause it's in a house, with people, that belong to the time where it came from (with the cpc 464 by the way, too), and I've got a strange feeling considering taking that setting apart (again). - Will see.

Do you want a full set of the components needed to add the Tape interface? It needs a relay (for the remote) an 8 pin header and connector some wire and a couple of other bits and bobs. I fitted it to one of my 6128plus's earlier this year and it is really easy. I had to buy the parts in multiple numbers so have several of each (Up to 99 for the resistor) left over, if you want me to put you together a kit of the parts just ask and I'll put one together.


Craig

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Offline flufduff

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Re: Amstrad 6128 plus CPC 6128 plus does not start
« Reply #8 on: 01:10, 31 October 14 »
Hi Bryce

Thanks for your reply again. The drive is ok I think - one LED is continuously lit (think some sensor to find if a disk is in, or sense the sector 0 mark or so), and if I say "CAT", the motor spins.

The ... rubber... rope... ribbon... ah: belt, however, has been complete ... marmelade :-) If I have a bit of time, I'll put something else in. When my original CPC belt died (probably more than a decade ago), I found that I could use very very normal household rubber rings of a certain size and use them as a perfect replacement. They cost pennies, and worked, so later on I started to shake my head when I saw the guys on ebay selling a single belt for 6 Euros... I've seen this newer drive has a slim belt though, but I may be able to find something in a box with tape drive belts :-)

Your question can almost motivate me to check immediately - but I should rather go to sleep. And - I don't have *any* 3" media here with me, I think, so I would probably not be able to test the drive completely anyway. But the head looks fine.

I've also got a printer and a cable from ebay - so I could try printing, too - but not today. (And I need some replacement ribbon, or color refill anyway.)

As I said - I'm quite confident that everything else will work. I would have been disappointed, if the machine had been dead all over - because it cost me some Euros, some a stressful travel experience, and time to clean it and try to make it work - but right now, I'm quite happy as it is. Actually, I could sit in front of it, turn it off and on and enjoy the yellow-blue start screen every time it appears. :-)
Ok, that's probably problematic for someone who should be grown up. But it's not merely about that machine. It's about *everything*, and the machine brings one particle of the "everything" from back then to today. You probably know what I mean :-)

At least, turning it on, does neither mean immediate information overload nor being stressed to work. I often said I wished back the computers where you could understand down to the bits what they did if necessary, and that could not operate faster than I could think. Like compilers that gave you a pause of just the right size - not so short as to keep you busy and stressed all the time, and not so long to make debugging runs too lengthy...

Oh you see, the old machine keeps dragging me off topic.

I'm also considering doing some case-colour-revival I've read about once, but think I won't have the time to do that soon.

Kind regards, Fluffduff
« Last Edit: 01:21, 31 October 14 by flufduff »
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Offline flufduff

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Re: Amstrad 6128 plus CPC 6128 plus does not start
« Reply #9 on: 01:17, 31 October 14 »
Hi Craig

That's indeed very nice of you, thanks. I've already seen the schematic for the relay (I think it made me find this site the last time) before I picked up the machine.

Normally, I should have relays, transistors and connectors available. I should actually use them from my own supply - in order to make that shrink rather than grow.

Still if I should not find the parts, I might ask you again. - The other thing is, just like the disks, the tapes in question are all at home (And there should even be a tape recorder with a remote in, that hasn't been used for tens of years...). - It comes to my mind that connecting the relay to some parallel or joystick input pin on a peecee and the cpc tape to the peecee sound jack would make a nice replacement tape on hard disk. Probably somebody has already done that...

But the most important thing is time. See, I must work tomorrow from 8:00 till literally open end, and open end might be Monday morning. It's very difficult to put the machine away without switching it on, being happy about the  blue screen and playing with basic programs again... so if you guys keep suggesting new topics to me all the time, that's indeed very nice, but it won't improve my sleep deficit!!!! :-) ;-)

You know, this old stuff is a very infectious disease for my real life time management...

Kind regards, Fluffduff
« Last Edit: 01:20, 31 October 14 by flufduff »
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Offline flufduff

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Re: Amstrad 6128 plus CPC 6128 plus does not start
« Reply #10 on: 01:20, 31 October 14 »
N.B.:

I just remember that - *IF* it is needed by anyone:

A long long time ago, I've once made a PC program as a replacement for a dictaphon player. That does just that: Accept a wave file, and when you press some buttons at the printer port or the joystic port, start and stop playing (or even rewinding etc.). That would make an exact replacement for a remote controlled tape drive, at least as far as playing is concerned. It does not record (yet).

Kind regards, fluffduff
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Offline chinnyhill10

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Re: Amstrad 6128 plus CPC 6128 plus does not start
« Reply #11 on: 02:17, 31 October 14 »

Still if I should not find the parts, I might ask you again. - The other thing is, just like the disks, the tapes in question are all at home (And there should even be a tape recorder with a remote in, that hasn't been used for tens of years...). - It comes to my mind that connecting the relay to some parallel or joystick input pin on a peecee and the cpc tape to the peecee sound jack would make a nice replacement tape on hard disk. Probably somebody has already done that...



Or you could just buy a car cassette adaptor, mod it slightly and run the cable through the case and out the back. Works a treat on my 464. Cost me all of a couple of quid and 20 minutes of my time.
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Offline flufduff

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Re: Amstrad 6128 plus CPC 6128 plus does not start
« Reply #12 on: 23:55, 03 November 14 »
Hi Chinnyhill10...

Thanks for this suggestion. I don't exactly know what you mean with car cassette adaptor? The one that looks like a cassette and goes into the auto radio? Well, I need to be able to read normal tapes with the setup, because I want to use the machine to transfer my own old "works" :-) to a PC. But if a 3.5" jack is on the machine, such an adaptor can be plugged in.

Anyway, I think there should be the possibility to turn an audio file on the PC into a virtual cassette recording for a CPC emulator... But I find it more consistent to use the real thing. Even now I haven't had the time to show it to the little boy around here who usually tries out all things with keyboards on them. Will see...

After all - I'm quite happy that I have it now. Also have given it a new drive belt, and put it all back together for now, so it has got a bit more compact again. I'll tell you when I do additional stuff with it, just don't know when I'll be able to.

Once again, thanks for all your replies - it's nice to see you care - and kind regards to you all!

Joerg
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Offline CraigsBar

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Re: Amstrad 6128 plus CPC 6128 plus does not start
« Reply #13 on: 19:16, 05 November 14 »
First tape socket kit assembled for seanb. If anyone else needs one I have 3 relays left.
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