Amiga 4000 audio problem (one for castellen)

[countzero]

I got this A4000 mobo with audio problem (no sound from both channels) off ebay some time ago (as-is, grrr). Recently I got some time to fiddle with this baby and see what's wrong with the audio. First I started with the caps, and I desoldered all caps and fit in new ones. unfortunately this didn't solve my problem, there was still no audio. So I proceeded to the next step and measured the voltages on some components as explained by castellen's excellent repair guide here. Unfortunately, I got some very strange readings. I measure -9v where I should have +12. Most other levels are screwed too. I'ld be glad if someone could give me an advice what to do next. Are u402 and u403 dead ? or do I have some short somewhere which messes with the 12v line ?

here are my readings,
U402
1- -8
2- -8
3- -6
4- -9
5- -6
6- -8
7- -8
8- -8
9- -1
10- +2.5
11- -12
12- +2.5
13- -1
14- -8

U403
1- -8
2- -8
3- 0
4- -12
5- 0
6- -8
7- -8
8- -9

PSU seems to be fine.

[countzero]

I've solved this issue a while ago, it was missing 12v as castellen put it. Strangely, problem was a fix done by the previous owner that escaped my attention, near the power socket (totally unrelated to audio area). Appearantly 12v track along with a diode burned out and the previous owner replaced it, but the solder was dead on one end, it wasn't inducting. 12v was missing from the whole board. After a quick fix, my a4000 blasted my speakers with pure joy after god knows how many years

now I'm unto another problematic a4000 board which has a mouse port that doesn't recognise horizontal movement. Sounds easy enough but I couldn't locate a problematic part at the first look. might bug you people again in a short while...

many thanks for all the replies.