Keyboard or Mainboard problem

[arnoldemu]

Just had a thought. If a test program was designed to be run from |cpm then you could force a link on the board to boot com when cpc starts, that may make it possible to run some keyboard tests.

A better test program would run from Rom, but that needs extra hardware to start it putting it out of the reach of many.

[Bryce]

Bit 7 or D7 is stuck. All these keys are on the same bit but over multiple keyboard columns. Is there a short somewhere between keyboard and ay?

Yes, that's what I thought too, but I can't find the spot where it's happening.

Bryce.

[arnoldemu]

Yes, that's what I thought too, but I can't find the spot where it's happening.

Bryce.

I have attached a dsk I made.

If /exp is setup so disc rom is 0, the cpc will autoboot from this when started up. No idea if the plus will auto start I never tested it.


The display will show lines. Red blobs will appear when a key is pressed.

Without any keys pressed it should just be vertical lines. If keys are pressed, or held by the hardware red blobs will appear.

From left to right are the bits with a line, with the lines going down the screen.
Bit 7 on the left and bit 0 on the right.

From this it should be possible to work it out a bit more easily.

[talrek]

Ok, so we have exactly the same issue, good to know. The plus doesn't have a PIO, so that's not going to be the issue. However, I have noticed that this PCB also has problems with the floppy drive, does yours too? Also one other thing that I noticed. Mine has a French keyboard and an English ROM, what about yours?

Hopefully I can check it some more today and maybe find the solution.

Bryce.

English keyboard and ROM for me.
No problem with External Floppy drive.


With the joystick i have multiples characters before the arrows :

[Bryce]

Thanks, Talrek can try this, but unfortunately the floppy drive is dead on my PCB too, so I'd need to fix that first. I'll continue the manual search first.

Bryce.

[arnoldemu]

Thanks, Talrek can try this, but unfortunately the floppy drive is dead on my PCB too, so I'd need to fix that first. I'll continue the manual search first.

Bryce.

If I create a cart version would that help?

Eventually I could extend it to detect and pin point the problem, and add other testing to diagnose other problems.

[Bryce]

It would be excellent, but no need anymore, I've found the problem. Here's what's normally on each scan pin (coming from the ASIC in my case):

[attach=2]

And here's what's on pin 1 of CP104 (ie: pin 80 of the ASIC):

[attach=3]

As you can see, the signal is inverted (or not being inverted to be exact), which is causing the mess. On Talreks CPC I suspect IC101 (74LS145) has failed, as it is responsible for these signals on a classic CPC. In my case the ASIC seems to have dropped an inversion stage All is not lost however, I'll cut the trace and add an external inverter and see if that can solve the internal failure.

Bryce.

Edit: Hmmm, looks like this is an ex-CPC. I added an inverter and it was still causing problems. Then I connected all pins up to my Logic analyser to see what's happening. Although the signal is now correctly inverted, the pulse is about 4 times longer than it should be and also not at the correct time. This isn't something that can be easily fixed externally, so we have a dead ASIC. Time to look at the second plus that Craig sent me. It has a questionable ABBA mod that needs to be removed and it currently boots to a blue border with yellow box, so RAM is the first suspect.

[talrek]

wooooowwww 
Ok if you say so.... i will try a good one so..


I keep in touch 

[arnoldemu]

wooooowwww 
Ok if you say so.... i will try a good one so..


I keep in touch 

I would be interested to see the result from my programming because then i could detect this in code and tell somebody to try that chip first.

[Bryce]

Unfortunately my PCB wasn't in a state to read disks, but Talrek could still test it on his CPC. If not, it's relatively easy to simulate this failure, so I can test it later if Talrek doesn't.

Bryce.

[CraigsBar]

It would be excellent, but no need anymore, I've found the problem. Here's what's normally on each scan pin (coming from the ASIC in my case):

[attach=2]

And here's what's on pin 1 of CP104 (ie: pin 80 of the ASIC):

[attach=3]

As you can see, the signal is inverted (or not being inverted to be exact), which is causing the mess. On Talreks CPC I suspect IC101 (74LS145) has failed, as it is responsible for these signals on a classic CPC. In my case the ASIC seems to have dropped an inversion stage All is not lost however, I'll cut the trace and add an external inverter and see if that can solve the internal failure.

Bryce.

Edit: Hmmm, looks like this is an ex-CPC. I added an inverter and it was still causing problems. Then I connected all pins up to my Logic analyser to see what's happening. Although the signal is now correctly inverted, the pulse is about 4 times longer than it should be and also not at the correct time. This isn't something that can be easily fixed externally, so we have a dead ASIC. Time to look at the second plus that Craig sent me. It has a questionable ABBA mod that needs to be removed and it currently boots to a blue border with yellow box, so RAM is the first suspect.

Oh Shambles!!


Sorry Is the 2nd one the one that originally had an STS Copymod on it? I don't remember either of those actually having an ABBA switch?


Craig

[arnoldemu]

Unfortunately my PCB wasn't in a state to read disks, but Talrek could still test it on his CPC. If not, it's relatively easy to simulate this failure, so I can test it later if Talrek doesn't.

Bryce.

I think I could simulate it too. I am guessing that you can press any key, and when you do the result is replicated across all keyboard lines. So that pressing a joystick direction will give a different set of keys than delete, but this assumes nothing shows until you press a key.

An alternative is a key always appears stuck because an input always stays low, so both could be tested for.

I think if the membrane failed you could see all keys in a column be unresponsive, or more than one if it is a partial failure.

[Bryce]

Oh Shambles!!


Sorry Is the 2nd one the one that originally had an STS Copymod on it? I don't remember either of those actually having an ABBA switch?


Craig

CPC Laptop.



The socond one had a chip piggybacked onto the 74HC14, some tracks cut and wires hanging from the floppy port..... and now works

Bryce.

[talrek]

IT WORKS !!!!!!!!!!!!!!





It was the problem... damn IC 


So, i'm sorry i am not able to test your disk as the CPC works now   

[Bryce]

Result! Congrats.

@TFM: Guinness or Reissdorf Kölsch please

Bryce.

[talrek]

Yes really thank you !!!
If you come by France near Bordeaux i would offer you a beer 

[Gryzor]

Marking solved!

[TFM]

Result! Congrats.

@TFM: Guinness or Reissdorf Kölsch please

Bryce.

Ok, Guinnes ready for pick up. However it wasn't the BASIC ROM either   Happy to see that the problem is solved. 

[zhulien]

hi All,


I bought a 6128+ just recently on ebay, and although it was advertised as working it has the exact same (observed) problem described here as per the image in reply#20.  I have 2 6128+ machines and I have swapped keyboards and they both show the same problem on the faulty 6128+ but  both work perfectly on the good 6128+.  On the faulty one however I found out that the guy who sold it to me modified the 6128+ to use a different PSU plug which is another annoying thing (that wasn't advertised).  Whether he did or not, one of the smaller chips has an extra wire wired to it on this 6128+ also.


Any queues as to what I should look at to isolate and fix this problem?


Thanks, Julian

[Bryce]

Unfortunately, this probably means that the ASIC is faulty and this isn't a part that you can get, other than removing one from another Plus. Which is kind of pointless. That's an ex-Plus you have there.

Sorry,

Bryce.

[zhulien]

I guess that sucks... could there be a firmware fix for it?  if the del key is held down, those same extra characters appear but it does register as a del key too.

[Bryce]

On the plus I tested there were several additional problems inside the ASIC, no amount of Firmware fiddling is going to fix this.

Bryce.

[gladders]

Hey all so I have a CPC 464 which boots up seemingly pretty well to a small HDTV I have (although a slight image wobble which I'll leave for now)


But the keyboard isn't entirely working.


The Caps lock, c, b, n, m, /, \, plus 2 and + on the numpad won't respond. According to the technical specs, this makes sense - one of the lines on the matrix of the membrane has expired.


I've opened up the 464 and given everything a good clean and looked at the membrane. It all looks intact, so I guess a new membrane is needed.


Does anyone know where I can get one?

[dragon]

Unfortunately, this probably means that the ASIC is faulty and this isn't a part that you can get, other than removing one from another Plus. Which is kind of pointless. That's an ex-Plus you have there.

Sorry,

Bryce.

I know one shop selling asic chip but is no cheap .

Semiconductor: 40489 - AMSTRAD-IC GATE ARRAY

Amstrad made much more componets that plus computers  builded .

[arnoldemu]

I had a 6128 in storage. I had cleaned the membrane carefully.
But some keys didn't work. I removed the membrane carefully cleaned the lines on the membrane where it goes into the connector. I used a bit of spit and cleaned it very carefully and dried it.

now all my keys work again!

So in my case, the membrane was good and I either needed to re-insert it again, or the end had become a bit dirty.

Two times I've done this and both times it worked great.

So try this if you've not done this already.