repairing old c64 - UK's 1984 model

[Raf]

hello. I'd like to repair my old breadbox. yesterday I've got a 64c '87 made in germany which has got exchangeable chips with that broken one so I started investigating it further...

here is list what I tested , what I see and what I suppose

machine is dead after powerup (just black screen).
kernal rom is dead.
SID is dead.
both CIAs are good - I desoldered then , socketed them and tested in working c64e.
VIC is good.
keyboard was broken (some keys didn't work) but I replaced it.

exchanging rom with working german one didn't help.
exchanging 6510 with 8500 didn't help - dunno if 6510 is broken in this machine and dunno if my 8500 is good , and I dunno if 6510 is exchangeable with 8500 anyway - any help?

RAM seems okay - not hotter chips or such
other roms are also warm , but kernal was just _HOT_

maybe it's just problem with PLA?

[Ruud]

Raf wrote:

hello. I'd like to repair my old breadbox.
....
maybe it's just problem with PLA?

Dzien dobry RAF,

IMHO in most cases the PLA is to blame. But a very hot ROM isn't a good sign either.
Anyway, I can send some parts. Drop me an email and we can discuss things in private.
'Ruud.Baltissen at ABP.nl' and 'Ruud at Baltissen.org'

[Raf]

anyway there is also a diary I made for this one , thanks for effering help:

late nov 2004 - I bought old (1984), broken and dirty C64 , case is broken (there is no
plastic that keeps rear part of the case together) , one key is missing and
it's "socket" is broken - that means that no kay exchange can be made .
after powerup there is only black screen. power indictaor diode was insterted incorrectly
so it seemed that someting went wrong with power block but fortunately
it's okay

ealry dec - I made some checks... which drove me to PLA or kernal ROM as the most probable
defected chips.

- "power unit" inside - ok
- no short circuits on busses
- CPU seems to be good
- KERNAL ROM gets very hot
- RESET signal is working (external drives are resetting with c64)

11 dec 2004 - I exchanged complete keys with model from 1985 , now at least it looks better
AND KEYS AVTUALLY WORK AS OLD KBD WAS REALLY BROKEN , NOT ONLY THE KEY WAS MISSING.

14 dec 2004 - I'm preparing to make "magical" things to see IRQ NMI AEC
and clock phase2 activity on screen . in new c64 - i made this with success and theoretically I found out how to install this feature in old c64 also.

14 feb 2005 - I desoldered rom and insterted precious socket for it , also tried to go with new c64's rom
but w/o succes (possibly that rom also is broken , my adapter may suck or it's not only ROM related problem with this c64...

15 feb 2005 - unsoldered keyboard+joy+NMI CIA and inserted normal socket
tested CIA in another c64 - it's okay

4 Aug 2005 - got c64c so I tested some chips.. VIC is GOOD , ROM is dead , anyway exchanging CPU , ROM and such didn't help