broken a500+

[orange]

well i finally got a500+ but its broken.
the kickstart screen shows up and workbench works, mouse too and RAM is OK.
but games crash and there is no sound.

battery had started eating the traces, but i checked them with multimeter and they seem fine. (replaced it with lith and clock is ok)

also R408 replaced

what to do?

[orange]

paula gets a bit warm quickly more than fat agnus.
can i replace paula and cia chips with the ones from a500 ?

[Zac67]

paula gets a bit warm quickly more than fat agnus.
can i replace paula and cia chips with the ones from a500 ?

Check the capacitors for leakage - they age and leak.
Paula and CIAs are the same for all Amigas (apart from those with PLCC package).

[guest7146]

Check the capacitors for leakage - they age and leak.
Paula and CIAs are the same for all Amigas (apart from those with PLCC package).

Yep, +20 years is actually very good going for electrolytic caps.  Check for signs of bulging and/or weeping.  Any that show these physical signs definitely are faulty, but often electrolytics can be faulty and not show any physical signs at all.  So don't assume that if they're not bulging or weeping then they must be good.

I've heard of faulty caps causing this sound issue before actually.  Perhaps someone else with experience of this fault will come by and volunteer which capacitors to check/replace.

AH.

[orange]

oki, so my next step is to replace paula. I'm a bit worried that a500+ 'motherboard' might damage the 'new' paula.
would it be wiser to put the 'old' paula from a500+ into known good a500 and see if it works? (if i try that would it damage some other custom chips or something)

edit: come to think of it, its a shame they didnt put some audible beep or something in 'poweron-selftest'. they could have at least put some audio in early startup menu, sigh..

[orange]

i tested the paula from a500+ and it works fine.
hm, prime suspect here seems to be battery leak corroding traces.
its hard to test that one..

could one of CIA chips be responsible for no sound?

[rkauer]

Sound is generated only by Paula. But after her there is some op-amps, replace those.

 Through-hole capacitors from 85-90 era are very reliable, no need to replace those if no problems.

[orange]

Check the capacitors for leakage - they age and leak.
Paula and CIAs are the same for all Amigas (apart from those with PLCC package).

what about Gary?

[Zac67]

what about Gary?

Gary's the same for A500, 500+, 2000(B). Never had a damaged Gary though...

PS: forgot the CDTV, of course

PPS: The easiest way to find out where sound is missing is with a simple signal detector. You can use any headset, just connect ring to ground and tip to a somewhat pointed probe (the 3.5 mm plug is a bit too bulky). Make sure you don't short the signal to ground or 12V, Paula's a bit delicate here.

Start from Paula's pins 30 & 31 and work your way over the EMIs E305 & 306, U14 (in on pins 9 & 13, out on 6 & 14, 2nd stage in on pins 3 & 5, out on 1 & 7) towards outbound caps (C324,325,334,335) and EMIs (E302,303).

Care for the SM? Just pm you email address and I'll send it over (2.3 MB PDF).

PPPS: never mind, found the address from the 514256 chip 'deal'.