A3000 DiagRom Cyan color issues

[Sasha]

Good day,

I recently purchased an Amiga 3000, saw that it had prior battery damage around Paula and Denise and green socket discoloring fanned out around 2 cm from where the battery used to be. ( But it was booting)

I replaced Paula/Denise sockets, the 04/LS74 socket and chips, used white vinegar and washed the board.

Noticed that via around the damage area had green corrosion plus all the chips mentioned above. All is cleaned out now.

Board boots into (KS Green) and (Diag Rom Cyan) color. I see no rs232 communication via the null serial cable RX->TX TX->RX GND->GND

Purchased a scope which should arrive this week.

What I noticed that GND and VSS are almost shorted.
Bus transceivers around the zorro socket next to memory chips and GALS are running hot.

Took out memory chips and the board comes up but black screen instead of Cyan color
I have asked someone to replace the caps and also give the board an ultra sonic bath.
Appreciate any additional suggestions.

Thanks,

[Vypr]

1 - There is normally very low resistance between 5V and GND on the A3000, Mine is showing 28 ohms and a friend has one at only 8 ohms. I spent days chasing that round the board before realising it was normal.

2 - The GALs do run hot under normal operation, it was a common point of failure, You can replace them with PALs that run cooler and more efficiently.

3 - Check the traces on Paula and Denise, the cleanup may have damaged traces already brittle from the alkali damage. Unfortunately there is no A3000 board on amigapcnb.org but if you grab a copy of Sprint Layout and download Chucky's ReAmiga 3000 Sprint files from http://www.reamiga.info/?page_id=40, that's pretty a much a 1:1 recreation of the baord and it can help you trace signals round the board.

[Sasha]

Originally Posted by Vypr

1 - There is normally very low resistance between 5V and GND on the A3000, Mine is showing 28 ohms and a friend has one at only 8 ohms. I spent days chasing that round the board before realising it was normal.

2 - The GALs do run hot under normal operation, it was a common point of failure, You can replace them with PALs that run cooler and more efficiently.

3 - Check the traces on Paula and Denise, the cleanup may have damaged traces already brittle from the alkali damage. Unfortunately there is no A3000 board on amigapcnb.org but if you grab a copy of Sprint Layout and download Chucky's ReAmiga 3000 Sprint files from http://www.reamiga.info/?page_id=40, that's pretty a much a 1:1 recreation of the baord and it can help you trace signals round the board.

Thank you, I was looking for the trace files. Any idea why they are not on pcnb?
Do you know where I can get the PALs?

[Vypr]

I don't think they had a proper board layout that can be imported. Chucky offered his Sprint layout but I believe there was a problem with Sprint not using netlists.

You can replace the PAL16L8 chips (U202, U203 & U714) with SPLDS, these ones should work:

https://www.mouser.co.uk/ProductDetail/556-AF16V8C7PU

And you can find the code to flash them here:

https://www.amigawiki.org/doku.php?i...s:pld_download

I haven't been able to find anything to replace the PAL16R4 with (U701)

Also, finding something to flash them with may be a bit trickier, I tried my TL866II and even though it said I successfully flashed them when I tried to read the contents back they showed up as unflashed so I ended up just reusing the original chips.

[Sasha]

Thank you Vypr. It is interesting that another person told me that he is also having issues programing the PALs.
Time to take some aspirins and start the grunt work tracing. I will report with my findings moving forward.

[Vypr]

Good luck! I eventually gave up trying to get mine working and bought one of Chucky's ReAmiga 3000 boards

[Sasha]

Update:

Found a trace that was cut around 80% on Denise D8 pin under the socket going to the memory area. Trace was still intact but I am sure if TDR is used, it would show reflection issues and also extra resistance at the problem trace point.
I actually remember damaging the line myself desoldering the socket. Here is California the air is so bad that I actually sneezed and saw my tweezer accidentally cutting the line partially.

Thank you for your help Vypr.