From: Andreas Meerbann on 16 Nov 2009 05:34
> Many thanks to Andreas Beermann too by whose advice and tips I learned
> a lot of things.
I'll inform this guy about your thankfullness when I meet him next
In case you've enjoyed your experiences a little you might want to
participate in (de.)sci.electronics as well. Loads of people like
From: Peter Schepers on 16 Nov 2009 10:19
In article <7mas27F3gpo7qU1(a)mid.individual.net>,
Paul F�rster <paul.foerster(a)gmx.net> wrote:
>... first of all the good news first: *Success*! Yippie! It's working
Even reading through this whole post, I still don't know what was really
wrong. Do you think the traces for D4-D7 were somehow damaged before
starting to try to fix things?
>I accidentally made some pins a little too hot and so
>a few traces came out with the chip. :-( I measured everything through
>according to schematics and put wires where I accidentally ripped off
I found this issue affects the 64C the worst. I despised working on those
as traces would lift or ;plate-through holes would come out...
>Was multi-layer possible back when Commodore printed these boards?
I wish I had one to check. Yes, it was possible.
>Btw., ceramic caps don't have + or -, only electrolytic capacitors do,
>right? Since I didn't know + or - of the ceramic lenses I put them in
>with the inscription in the direction as they are on the other board.
Normal ceramics usually don't have any orientation. Tantalum do, but they
are visibly different.
>Signals appeared as you listed them in column 1. Ok, not all. Pin 1
>showed strange values. But you recall that I mentioned the board has
>been cut. The connection between pin 1 and the diode has been cut. So I
>verified it with Ruud's board and put a wire there too, just for the
>sake of completeness, even though SRQIN (what does SRQ stand for
>anyway?) is not used. That gave me a high value on pin 1 too. I
>connected a drive. Checked it and everything works fine.
SRQin is Serial Request In, and is supposedly unused except it is also on
the tape port. It isn't used in the C64 for the serial port.
>That was a real tough one for an electronics newbie like me. But I've
>learned a lot. Thanks again. :-) I hope such a desaster never happens
>again because it already costed me 10 days which I would have liked to
>use for something more constructive. At least I have a very fine and
>big printout of the schematics, a new (de-)soldering station and quite
>invaluable knowledge now.
Since you seem to not have found any shorts or opens on the serial out
side of the CIA, have you inspected the D0-D3 traces on the board between
the CHAR ROM and the CIA to see where the fault could be?
From: Paul Förster on 16 Nov 2009 10:41
On 2009-11-16 11:34:42 +0100, Andreas Meerbann <andijunk(a)gmx.de> said:
> I'll inform this guy about your thankfullness when I meet him next
> time... ;-)
.... yes, and give him a beer on my account. :-P
> In case you've enjoyed your experiences a little you might want to
> participate in (de.)sci.electronics as well. Loads of people like
> Andreas there!
.... well, I don't do this for enjoyment but rather to revive old
functionality which had been cut off in the true sense of the word. So
I'm doing this with connectors and put them in the case because a
complete board wouldn't fit. So the connectors were cut off. But thanks
for the hint. Should I encounter more problems then I will definitely
look there. After all, there's still the issue with the 50 Hz TOD clock
generation and possibly creating a 5/12V DC & 9V AC power supply
open... But that one has time.
From: Paul Förster on 16 Nov 2009 10:49
On 2009-11-16 16:19:40 +0100, schepers(a)ist.uwaterloo.ca (Peter Schepers) said:
> Even reading through this whole post, I still don't know what was really
> wrong. Do you think the traces for D4-D7 were somehow damaged before
> starting to try to fix things?
.... yes, possibly. I measured everything many times and all the lines
have always measured ok. Only the last time I checked, there was no
connection on D4-D7 on CIA2. I suspect it was hairline cracks or
something. I really don't know.
> I found this issue affects the 64C the worst. I despised working on those
> as traces would lift or ;plate-through holes would come out...
.... I never had problems with bridge openings. There seem to be little
rings inside. I only had problems with traces not holding on to the
> I wish I had one to check. Yes, it was possible.
.... well, I can't check. At least I don't know how. But at many points
it's hard to see where traces lead because they seem to stop at some
place and not show up on the other side of the board.
> Normal ceramics usually don't have any orientation. Tantalum do, but they
> are visibly different.
.... and marked accordingly I figure...
> SRQin is Serial Request In, and is supposedly unused except it is also on
> the tape port. It isn't used in the C64 for the serial port.
.... it is on the tape port. And the tape connector worked fine. At
least until my serial repair action. Video and tape connectors will be
next to refit.
> Since you seem to not have found any shorts or opens on the serial out
> side of the CIA, have you inspected the D0-D3 traces on the board between
> the CHAR ROM and the CIA to see where the fault could be?
.... I have checked all 40 CIA2 pins. D0 to D3 measure fine from one CIA
to the other. But yes, I had problems getting CIA2 out properly. Maybe
I damaged something on those four lines. I really don't know. At least
up to now, it's working again. :-)
Btw., the strange resistance on RP6 pins 4 and 6 remain. But hey, it's