Amiga 1200 crashing and freezing

[orange]

Please help me. For years I had this problem with A1200:
When I turn it on, if its not used for 15 min, everything works fine (after). But, if I try to start games, DOpus, anything else within 15 min of power up, Amiga freezes and crashes. It seems that its more serious when 4Mb RAM card is attached (and I really need it). When I disconnect 2,5"HDD and 4Mb RAM, it almost works perfectly (I can't remember if it crashes at all then)


There is someone that had similar problems with expanded Amiga 1200:

http://groups.google.com/groups?selm=CC9q3z.2qC%40dcs.ed.ac.uk&output=gplain

The only problem is that I have 2,5" HDD and connecting to PC power supply (200W) didn't solve anything. Still, I get the same crashes in first 15 min of use. After that "warm up" time, everything works fine. I could leave A1200 on 24/7 but..
Someone told me it could be the bad capacitor.
What is wrong with my A1200 in your opinion?

[orange]

Its actually connected to A500 PSU now, but it makes no difference. For some strange reason it worked fine yesterday, no crashes. Though it was a HOT day. There are so many solder points at motherboard, I can't check them all.
Is there any "usual" reason for freezing?
Rarely it crashes with blue/white stripes across the screen.

I had done a very stupid thing with A1200 once: connected 2,5" HDD to wrong ROW of pins. Could that have damaged 68020 (or something else) somehow ?

[orange]

I did some additional tests, here are the results:

When startup-sequence contains only memtest program that tests RAM "forever", and I don't use mouse or keyboard, everything is OK.
Then I put CLI command "list ALL" into startup-sequence, so that HDD works "forever". It worked fine, too, no freezing.

The obvious conclusion would be that something is wrong with chip controlling mouse and keyboard (was it CIA?). It somehow freezes A1200 if not heated.
What is the number label of CIA in A1200, so I could try to resolder it?

[orange]

I have found this post (from 1996)and it seems just like mine problem :

i have a problem with my a1200: when run in dblpal alice heats up and causes screen
corruption which makes the machine unuseable. If alice gets hot enuff the problem goes away -
or if she stays cool, but unfortunately at my normal room temp the damn chip hits just the
right temp to be annoying. other than cooling or insulating (dodgy) the chip, is there
anything i can do to solve this (some sort of h/w hack or summin)  - this is not just a one
off either - all new a1200 motherboards (from amitech) have this problem (i used to work for a
company who sold 1200's and i tested about 14-15 over different periods of time inc different
batches so i beleive it's common anyway)

:-o

[orange]

So, that timing fixes (R118, E123c...) wont help me at all?


(Budgie REV -01 and -02
   Remove E123C and E125C from the A1200 motherboard
   Add 470 ohm pull-up at pin 43 of U2, ie the Alice chip
   Change R118 from 470 ohm to 220 ohm)

I don't know where to look for solution anymore :-(