Hello everyone !
Here is my problem:
I have a CPC 6128 Plus. Everything works very well except: the 5,6,R,T,F,G,V and B keys.
during the test with my diagrom these keys activate the joystick directions and shot 1 and shot 2.
Under basic they write anything.
My tests:
- Keyboard tested on another CPC 6128 Plus: Test ok
Another keyboard on My CPC: Test KO does not work, same problem.
- I changed the AY to an 8912 (removing the 2.2Kohms resistance network): no changes
- I cleaned the keyboard connectors (I read this on the forum): No changes.
So I put back the original AY 8912 /P with the resistance network.
I also just read on the forum that it would also be necessary to remove the resistance network which is original on it. What do you think?
I admit I'm a little lost here.
A little help would be welcome.
I'll give you photos of the results, key by key.
thanks in advance
Willow
the rest of the photos
thanks
willow
Hi,
A good cleaning of the membrane and: Réparation du clavier des CPC+ [Quasar Net] (http://quasar.cpcscene.net/doku.php?id=electronique:reparation_clavier_cpc_plus)
Quote from: willow3411 on 18:46, 01 December 24I also just read on the forum that it would also be necessary to remove the resistance network which is original on it. What do you think?
Might help. I had to do that on my 6128 Plus. It worked fine but suddenly had some issues. Removing the network resolved it.
Quote from: eto on 18:57, 01 December 24Quote from: willow3411 on 18:46, 01 December 24I also just read on the forum that it would also be necessary to remove the resistance network which is original on it. What do you think?
Might help. I had to do that on my 6128 Plus. It worked fine but suddenly had some issues. Removing the network resolved it.
Hi eto
I'll test this tomorrow morning.
THANKS
Willow
You can check with an oscilloscope whether there is a 50Hz signal on the Y1-Y10 lines (second keyboard ribbon). You connect the oscilloscope probe between +5V and the next pins of the Y connector.
Quote from: eto on 18:57, 01 December 24Quote from: willow3411 on 18:46, 01 December 24I also just read on the forum that it would also be necessary to remove the resistance network which is original on it. What do you think?
Might help. I had to do that on my 6128 Plus. It worked fine but suddenly had some issues. Removing the network resolved it.
hello,
Well I removed the 2.2Ko resistor network.
That didn't change anything :(.
I took the opportunity to put back a new AY: Same result...
I'm going to take measurements with an oscilloscope but that won't solve my problem....
willow
Are you sure nothing is connected to pin 8 on second joystick port?
Quote from: ZorrO on 09:37, 02 December 24Are you sure nothing is connected to pin 8 on second joystick port?
hello,
no I don't have anything connected to it.
Could it be defective?
thanks
willow
Quote from: willow3411 on 09:46, 02 December 24Quote from: ZorrO on 09:37, 02 December 24Are you sure nothing is connected to pin 8 on second joystick port?
hello,
no I don't have anything connected to it.
Could it be defective?
thanks
willow
Hi Willow,
there's a bunch of small diodes between the AY and the ports. Check that these are all still working and aren't shorted anywhere.
Bryce.
Quote from: Bryce on 10:24, 02 December 24Quote from: willow3411 on 09:46, 02 December 24Quote from: ZorrO on 09:37, 02 December 24Are you sure nothing is connected to pin 8 on second joystick port?
hello,
no I don't have anything connected to it.
Could it be defective?
thanks
willow
Hi Willow,
there's a bunch of small diodes between the AY and the ports. Check that these are all still working and aren't shorted anywhere.
Bryce.
hi Bryce,
I just tested them all.
they are ok
thanks
willow
Quote from: Bryce on 10:24, 02 December 24Quote from: willow3411 on 09:46, 02 December 24Quote from: ZorrO on 09:37, 02 December 24Are you sure nothing is connected to pin 8 on second joystick port?
hello,
no I don't have anything connected to it.
Could it be defective?
thanks
willow
Hi Willow,
there's a bunch of small diodes between the AY and the ports. Check that these are all still working and aren't shorted anywhere.
Bryce.
hi Bryce,
just one question:
Couldn't this come from IC108?
the 74HC4051N?
Quote from: willow3411 on 10:45, 02 December 24Quote from: Bryce on 10:24, 02 December 24Quote from: willow3411 on 09:46, 02 December 24Quote from: ZorrO on 09:37, 02 December 24Are you sure nothing is connected to pin 8 on second joystick port?
hello,
no I don't have anything connected to it.
Could it be defective?
thanks
willow
Hi Willow,
there's a bunch of small diodes between the AY and the ports. Check that these are all still working and aren't shorted anywhere.
Bryce.
hi Bryce,
just one question:
Couldn't this come from IC108?
the 74HC4051N?
I don't have access to the service manual at the moment. Are the non-working keys all in a row or all part of a column? That will tell you whether it's IC108 or the AY that's the cause.
Bryce.
Quote from: Bryce on 16:54, 02 December 24Quote from: willow3411 on 10:45, 02 December 24Quote from: Bryce on 10:24, 02 December 24Quote from: willow3411 on 09:46, 02 December 24Quote from: ZorrO on 09:37, 02 December 24Are you sure nothing is connected to pin 8 on second joystick port?
hello,
no I don't have anything connected to it.
Could it be defective?
thanks
willow
Hi Willow,
there's a bunch of small diodes between the AY and the ports. Check that these are all still working and aren't shorted anywhere.
Bryce.
hi Bryce,
just one question:
Couldn't this come from IC108?
the 74HC4051N?
I don't have access to the service manual at the moment. Are the non-working keys all in a row or all part of a column? That will tell you whether it's IC108 or the AY that's the cause.
Bryce.
@Bryce
Thank you for the always very good advice.
these are the keys 5 6 R T F G V B which do not work
so I would say a column?
Willow
All these keys are in keyboard line 6, there seems to be an interruption of he connection.
See here:
http://cpctech.cpcwiki.de/docs/keyboard.html
Edit: I use this tool to take a look the keyboard matrix:
https://www.youtube.com/watch?v=wF0SbEJEO0A
Quote from: GUNHED on 17:50, 02 December 24All these keys are in keyboard line 6, there seems to be an interruption of he connection.
See here:
http://cpctech.cpcwiki.de/docs/keyboard.html
Edit: I use this tool to take a look the keyboard matrix:
https://www.youtube.com/watch?v=wF0SbEJEO0A
Hi,
so if I understand correctly this can come from NEC 8255?
Willow
Quote from: willow3411 on 10:09, 03 December 24so if I understand correctly this can come from NEC 8255?
Afaik the Plus does not have a 8255. If I am not mistaken, the ASIC produces the row signals without further support.
Have you checked the membrane if it's dirty or if there are any cracks in one of the lanes?
Quote from: eto on 10:45, 03 December 24Quote from: willow3411 on 10:09, 03 December 24so if I understand correctly this can come from NEC 8255?
Afaik the Plus does not have a 8255. If I am not mistaken, the ASIC produces the row signals without further support.
Have you checked the membrane if it's dirty or if there are any cracks in one of the lanes?
Hi eto,
yes I think he confused it with a CPC 6128 Old...
Yes, I tested my keyboard on another CPC: it works very well (as indicated in my first post).
I'll check with the IC108 (as indicated by Bryce).
Otherwise it's ASIC :( no?
willow
Quote from: Bryce on 16:54, 02 December 24Quote from: willow3411 on 10:45, 02 December 24Quote from: Bryce on 10:24, 02 December 24Quote from: willow3411 on 09:46, 02 December 24Quote from: ZorrO on 09:37, 02 December 24Are you sure nothing is connected to pin 8 on second joystick port?
hello,
no I don't have anything connected to it.
Could it be defective?
thanks
willow
Hi Willow,
there's a bunch of small diodes between the AY and the ports. Check that these are all still working and aren't shorted anywhere.
Bryce.
hi Bryce,
just one question:
Couldn't this come from IC108?
the 74HC4051N?
I don't have access to the service manual at the moment. Are the non-working keys all in a row or all part of a column? That will tell you whether it's IC108 or the AY that's the cause.
Bryce.
@Bryce I already changed the AY.
I will test the IC108 (I received the part today)
willow
Quote from: Bryce on 16:54, 02 December 24That will tell you whether it's IC108
Just for curiosity and learning: How can IC108 cause this? I don't see any connection to the keyboard pins but only to the MUX pins of the ASIC.
Quote from: willow3411 on 10:54, 03 December 24Otherwise it's ASIC :( no?
Might be... but I have no personal experience with that kind of fault on a Plus, Bryce is definitely the most competent person based on his experience.
I would probably have done those checks in addition to the checks you already did:
- I would probably first check if there is a proper connection between the ASIC pins and the keyboard connector.
- If a single pin is not properly connected, somewhere must be a physical issue.
- If all pins are properly connected I would carefully check if I get a signal on pin 75 on the ASIC (row 6) and compare it to e.g. pin 74. Very careful to avoid shorts. Not sure how problematic a short is.
- If there is no signal only on pin 75, then I would expect it's the ASIC - and ask here/Bryce for confirmation or further help ;-)
Quote from: eto on 11:38, 03 December 24Quote from: willow3411 on 10:54, 03 December 24Otherwise it's ASIC :( no?
Might be... but I have no personal experience with that kind of fault on a Plus, Bryce is definitely the most competent person based on his experience.
I would probably have done those checks in addition to the checks you already did:
- I would probably first check if there is a proper connection between the ASIC pins and the keyboard connector.
- If a single pin is not properly connected, somewhere must be a physical issue.
- If all pins are properly connected I would carefully check if I get a signal on pin 75 on the ASIC (row 6) and compare it to e.g. pin 74. Very careful to avoid shorts. Not sure how problematic a short is.
- If there is no signal only on pin 75, then I would expect it's the ASIC - and ask here/Bryce for confirmation or further help ;-)
Testing with oscillo ?
Quote from: willow3411 on 10:09, 03 December 24Quote from: GUNHED on 17:50, 02 December 24All these keys are in keyboard line 6, there seems to be an interruption of he connection.
See here:
http://cpctech.cpcwiki.de/docs/keyboard.html
Edit: I use this tool to take a look the keyboard matrix:
https://www.youtube.com/watch?v=wF0SbEJEO0A
Hi,
so if I understand correctly this can come from NEC 8255?
Willow
Well, since the keyboard itself works, the problem seems to be "before" the keyboard connector of the 6128plus.
Maybe a broken trace between ASIC and the keyboard connector. You could take a look using a looking glass or a good near-distance photo.
Good luck! :)
Quote from: willow3411 on 10:54, 03 December 24Quote from: eto on 10:45, 03 December 24Quote from: willow3411 on 10:09, 03 December 24so if I understand correctly this can come from NEC 8255?
Afaik the Plus does not have a 8255. If I am not mistaken, the ASIC produces the row signals without further support.
Have you checked the membrane if it's dirty or if there are any cracks in one of the lanes?
Hi eto,
yes I think he confused it with a CPC 6128 Old...
Yes, I tested my keyboard on another CPC: it works very well (as indicated in my first post).
I'll check with the IC108 (as indicated by Bryce).
Otherwise it's ASIC :( no?
willow
Yes, sorry, I confused it with the Classic CPC. I was answering from my phone and without schematics. If it's a Plus, then you need to probe the ASIC pins that create the keyboard scan. However, if one of those pins has failed (which is something I've seen before) then there's not much you can do to fix it.
Bryce.
Quote from: McArti0 on 21:31, 01 December 24You can check with an oscilloscope whether there is a 50Hz signal on the Y1-Y10 lines (second keyboard ribbon). You connect the oscilloscope probe between +5V and the next pins of the Y connector.
y1-y10 are wires from asic.
Quote from: Bryce on 14:55, 03 December 24there's not much you can do to fix it.
If it's really just a single pin that is failing, would it be possible to replicate the functionality of this pin with e.g. a ATF16V8? Basically whenever there is a OUT &f6xx,&46 then activate the keyboard lane.
Quote from: eto on 19:10, 03 December 24Quote from: Bryce on 14:55, 03 December 24there's not much you can do to fix it.
If it's really just a single pin that is failing, would it be possible to replicate the functionality of this pin with e.g. a ATF16V8? Basically whenever there is a OUT &f6xx,&46 then activate the keyboard lane.
Yes, I've done it once, but it's a bit more complicated than what you describe. Each Y pin goes low in sequence for a certain time while all other Y pins stay high. By "NANDing" all the other Y pins (ie: if all others are high then output should be low - If any other Y is low output should be high) you can replace the missing pin with external components. Of course, this only works if only one Y pin is defective.
Bryce.
Next step: Check signal coming from ASIC, but try not to do a shortcut ;-)
Hello everyone!
Okay, here are the results of my tests:
ASIC HS on keyboard inputs.
I'm disgusted.
Thank you all for taking the time for me.
@Bryce you can put the post as solved.
see you soon
willow
My experience : open the CPC+, remove and fix again the the cable that connects the keyboard and the motherboard. It works for me