Gareth Magennis wrote in message
...


"N_Cook" wrote in message ...

I decided that lash-up too whisky. The digital seems quite well separated
from the analogue on the PA board and 2 lines seem to come from off board
to
p2 and p6 of an M5218 dual op-amp SIP via electros from CN1 p6 and p8.
Injecting 0.1V in those points carried through to both the speakers. That
CN1 header traces back to the display board with vol and balance pots on
it
so a job for tomorrow




Whenever I get one side missing in something like this, my first port of
call is usually the volume pot, as it is usually easy to access and scope,
and/or short both wipers together.

Its a handy part of the circuitry to find out whether its the front end or
power amp section.


Gareth.




I'll know for next time.
Low profile 7 pin ALPS 103B 502C pot, I could get tending to 0 fully CW and
CCW pins 2,4,6 but not another triplet of pins. I did not realise these were
bass compensation? centre tapped dual 10K pot tracks
p2,4,6 one pot with 5K mid tap p1
p2,3,5 mid tap p7
and p2 common to both tracks
presuambly compacted grease lifting the flimsy wiper, from getting inside.
Hopefully that was the problem rather than me not realising these were non
standard pots.
Will try tracing the p6/p5 upstream signal side back to the main processor
board or wherever for non-kbd testing purposes