hello,
My cpc 464 has a display problem (see photo)
I changed the Z80, the GA 40007, the CRTC, the ROM 40009, the AY and the RAMs
always the same problem.
do you have an idea ?
thank you in advance
willow
Since the same byte is output twice, I would suspect a defective multiplexer (74LS153). In this case most likely IC105.
Quote from: Fessor on 18:09, 30 October 22Since the same byte is output twice, I would suspect a defective multiplexer (74LS153). In this case most likely IC105.
Hello,
thank you for your very quick response.
I will test this tomorrow morning
many thanks
willow
by the way
I have a question so I don't fall asleep stupid tonight.
to test a 74ls153 multiplexer you absolutely need an oscilloscope?
thanks
No, a logic analyser would be the correct instrument to use.
Bryce.
ok thanks bryce
@Fessor It's ok for ic105
it works perfectly
there was also a problem with the AY (no sound but keyboard ok).
everything is ok for me
thank you so much
Quote from: Fessor on 18:09, 30 October 22Since the same byte is output twice, I would suspect a defective multiplexer (74LS153). In this case most likely IC105.
I like to learn something - so opportunity for me here to ask:
How did you identify IC105 specifically from the picture?
I mean there are 4 74LS153.
Is that because IC105 is working on A0 and it could be only that A0 is allways 1 (instead of switching)?
Quote from: SerErris on 19:21, 02 November 22Quote from: Fessor on 18:09, 30 October 22Since the same byte is output twice, I would suspect a defective multiplexer (74LS153). In this case most likely IC105.
I like to learn something - so opportunity for me here to ask:
How did you identify IC105 specifically from the picture?
I mean there are 4 74LS153.
Is that because IC105 is working on A0 and it could be only that A0 is allways 1 (instead of switching)?
Yes, that was what I assumed.
Since only the byte at the odd address was repeated and everything else was correctly addressed and displayed, only A0 came into question for read access from the CRTC/GA and since the CRTC and GA had already been exchanged, it could only have been the multiplexer.
Since the multiplexer is said to have been OK, I would be interested to know what the error was.
I think
@willow3411 meant, that he replaced IC105 and it is now okay?
Can you please confirm what the final solution was for others to learn from it?
Thanks
Quote from: SerErris on 00:26, 10 November 22I think @willow3411 meant, that he replaced IC105 and it is now okay?
Can you please confirm what the final solution was for others to learn from it?
Thanks
good evenign, how are you
I had seen the post,
yes I changed as indicated above the IC105 and everything works fine.
thanks again