A3000 don't boot (green screen)

[Mugo]

Tried a lot of things already.

When i power on, after about a second, the screen goes green for about another second, then goes black again. This continues on a endless loop. The power led also blinks in the known dimmed/full lit states, signaling a problem.

I've replaced the Fat Agnus, the Denise, Paula, and even the socketed RAM chips. Nothing changes.

I think the problem can be with the PAL chips in the memory circuitry (U202, U203, U701, U715).

Can someone experienced with this problem confirm or deny it? Any thoughts?

Also, is someone here able to provide me with spare (tested working) parts to replace these PALs? Of course, i'll pay for them.

Thanks!

[Mugo]

Err... forgot to mention the machine background.

This A3000 suffered heavy battery corrosion. Only the top copper layer was affected (as far as i can see).

Have repaired the broken traces, and replaced the damaged parts (some capacitors).

I THINK i did repaired all the damage, but who knows.

The owner, a friend of mine, can't remember if the machine had this problem before the corrosion got worst, so can't tell if the problem really is a result of this.

Anyway, the corrosion seems to have damaged a section of the board where is the scandoubler circuit only. And the Scandoubler is working fine.

I can upload a photo if it can help.

Thanks again!

[Mugo]

Hey guys,

Thank you all very much for your replies.
I'll try to sumarize your ideas in this single message.

Regarding the CPU card, this A3000 is stock. No CPU card.
I have an A4000 with a CPPC. But i'm not really inclined to try it on this A3000. Despite all the work it'll render to get the board off the A4000, i don't want to take this kind of risks here.
Unfortunately this is the only CPU card i have available.

As i said before, Paula, Denise and Agnus has been replaced by tested parts. All sockets where cleaned and checked for corrosion. I don't think the problem is bad contact related.

I can only think of some problem still related to the battery corrosion. Or the PALs.

I really want to try and replace the PALs. But i need a provider, as i don't have the equipment to deal with them.

I'm slowly checking all the connectios to the chips and parts that are in the corrosion area.

The problem is that i'm doing this by the schematics, and I don't have them in paper. I only have bad quality scans. It really is difficult (and a turn off too) to check the circuit integrity this way.

If only I could find a hires picture of the board unpopulated, so all the board traces could be seen. This would be a HUGE help.

Thank you all again!

[Mugo]

Hey Tone007,

Thank you very much for the link.
Will contact Eslapion. Seems that he can provide me exactly what i need!

Regards.

[Mugo]

@da9000:

Thank you very much for all your input and kindness. Very much appreciated!

And sure, i'll be happy to have the xrayed pics, if you ever take them.

Regards.