A500, Flashing Red LED

[vimfuego]

Hi All,

First post here but long time Amiga user and looking forward to getting back in to the Amiga scene again.
So I decided to fire up my old Commodore collection and both my C64's were still good, but the poor old A500 is not so happy.
Upon inspection it looks like the 512K expansion has suffered a leaky battery, it's probably a write off, problem is I think it's taken out some parts in the A500 when I powered it up as it was all working a year or so back when I last turned it on.

With the 512K expansion removed the symptoms are, the red LED flashes 10 short pulses, one long one. Caps lock LED lights up briefly on power up.
Video output is random rubbish, not red, green, white etc as some of the diagnostic screens are. It stays like that for 2 seconds then black screen for 10 seconds then rubbish (repeat over and over). I guess something is getting reset with it repeating.

I've re-seated all chips, still no good.
I've put a scope on some of the chips and it looks like the problem lies with the data lines DRD(15:0) on the Fat Agnus, they are being loaded down.
All data lines between the 68K and ROM are good, so the CPU appears to be running ok.

Is there anywhere or does anyone know what the typical symptoms are when 'x' chip fails on the A500? I suspect the Fat Agnus, but I don't have another I can swap chips with to confirm.

Thanks,
Ross

[rkauer]

Try to carefully sack the Agnus out and then reinsert it. If no avail you need to source another Agnus. What A500 revision you have?

[vimfuego]

Agnus has already been out and back in with no change.
It's a Rev 5 with KS v1.2

Cheers,
Ross

[rkauer]

Agnus 8370/8371 are common as mud and easy/cheap to buy.