A4000 Help - Black Screen

[Lamaman71]

Hi Folks,

A4000d.

Without ChipRam gets as far as a green screen. Pwr LED dull, then bright.
Diagrom Sluggishly displays over serial - first line of text/ credits - but quickly starts to write 010101 etc

With ChipRam black screen that eventually goes dark purple. No output to serial diagrom with the exception of a few blocks of random ascii.

Im stumped. Anyone seen this before?

[nikosidis]

Originally Posted by Lamaman71

Hi Folks,

A4000d.

Without ChipRam gets as far as a green screen. Pwr LED dull, then bright.
Diagrom Sluggishly displays over serial - first line of text/ credits - but quickly starts to write 010101 etc

With ChipRam black screen that eventually goes dark purple. No output to serial diagrom with the exception of a few blocks of random ascii.

Im stumped. Anyone seen this before?

Have you removed the Varta battery? Sounds like you got some burned traces on your mobo.

[Lamaman71]

Yes, recapped, battery removed, traces repaired, Ricoh removed....

[Lamaman71]

haha yes indeed - and Im sure he would have it fixed in a jiffy!. Problem is, well, I have a problem with problems - and its sat there languishing on my workbench, laughing at me everytime I go in there and, frankly, annoying me. alot. lol. arrrgh.

[Lamaman71]

So - I buzzed out the Chip Ram socket when I replaced it - it did need a bodge wire but everything else checked out ok.

The PSU is original - giving me a good voltages. I did, out of interest, try a new PSU just on the off chance - made no difference.

[Lamaman71]

I guess really, ive been looking at trying to understand the route to the chip ram - CPU is working, Kickstart is ok I guess - Chipram socket is populated - dodgy Brigette? - U212? not sure where to look next or even what to scope.

[Screechstar]

Hi - I've just had some fun restoring an A4000 rev B too so just wanted to try and help if I can (I'm no expert!).

Did you say you replaced the chip ram socket and checked continuity for all the socket connections up and under the board?
I ask as I had a via damaged by cap juice near C200 and the via's under U852 can get hit by battery juice.

Amiga PCB explorer is a fantastic resource to help check all these traces, if you haven't used it already.


Obvious stuff;
- J213 set to 2mb?
- INT/EXT jumpers correct (I would guess so, as you had a green screen)?
- Tried a different ram stick - I still get 2mb shown with a 2 or 8mb stick, FPM or EDO works for me. I've read that 2,8,32mb sticks are electrically 'double sided' even if the chips are only on one side.
- Used contact cleaner on the socket (in case any flux went wandering)?