Denise versions

Hi guys

I've recently obtained a defunct Amiga 500 rev 6a motherboard off of eBay.
Unfortunately, it doesn't post/display - simply gives a blank screen when powered. I've done the following:

- Checked that all socketed ICs are the correct way around
- Reseated all socketed ICs
- Checked the board for damage (see below *)
- Tried each socketed IC in my working board (same rev) - see below **

Results:

* Someone has done a rather poor job of trying to cut tracks and solder pads on JP7A and JP2. There's lots of scorch marks. Obviously this was an attempt to increase the RAM availability. I've cleaned off the solder and re-bridged the original pad.

** All ICs seemed to work fine... apart from these:
PAULA
GARY
DENISE
(given that these are the custom chipset which I think ism linked by Agnus, I expected Agnus to be faulty, but it seems fine).

Denise does sort of work in that it gives an image, but it seems corrupted in places. I'd put this down to a fault, but noticed that the Denise IC which works (from my working rig) has the following:
CSG
8362R8
4589 28
While the one form the non-working board has this:
CSG
8362R8
2889 28

Would the versioning info at the bottom of the IC make a difference?

Cheers for any help

[jimbob]

I think that's a production date code, same chip.

I'm not following you exactly - Are you saying Gary, Paula and Denise each caused your known good board to fail but Agnus from the bad board worked in the good board?

[Jope]

Yes, production dates. The revision for both is R8.

The chip that doesn't work is fried, that's all. :-)

Originally Posted by jimbob

I think that's a production date code, same chip.

I'm not following you exactly - Are you saying Gary, Paula and Denise each caused your known good board to fail but Agnus from the bad board worked in the good board?

Yep, unfortunately that seems to be the case. I think the previous owner may have botched a RAM mod, but can't be sure. Either way, those ICs will not work in my good board. I could try my known good ICs in the "suspect" board, but don't want to risk them.
I might have to just harvest components off of the board and then junk the rest - but I hate the idea of destroying a bit of history. Unless any has further ideas?

[EDIT] Is it worth trying to clean the IC legs up? Looking again at them, although not corroded, the do have a slight blackish discolouration (oxidisation?). If so does anyone have any recommendations for this kind of job? I.e. methods, chemicals, etc.