Studiomaster 162BPX audio mixer

[Mark Black]

My money would be on a bad IC1 with DC on the input pins.

Good to have that chip socketed anyway since it is direct-coupled to the outside world via the headphone jack.

[Jazz P Bass]

Thanks for the pdfs - I've already got them all for all the boards and ICs.

Actually, I posted the files for anyone else trying to follow this post.

[Kingell]

So

I'm back together and the headphone control no longer affects the LED display!!
All the outputs work except phones which are very quiet and distorted.

Also the left channel of the LED display is not working.
Now I suppose it's my soldering! Tiny circuits - tiny board - ho hum.

Many thanks for all the suggestions and help. Well done everyone - excellent.

I'll take out the million.5 screws again and see if I've bridged something or .......... whatever.

Wanders off mumbling into beard................................................... ..

Kind regards to all - outstanding!!

[Jazz P Bass]

Remove IC1 & see if the LED display works on both channels.

[Jazz P Bass]

Although that will not prove anything if the socket/ capacitor soldering is screwy.

[oc disorder]

It seems there are a number of grounds at different points.
eg


I presume the desk was working ok and then something happened.
If it was dropped there could be cracks in the pcb boards.
Perhaps the grounding screws are not making good chassis contact and need removing..cleaning
and re tightening.

[Jazz P Bass]

Yeah, that is why I suggested that the OP make darn sure IC1/ Pin 3 is connected in proper order.

[Kingell]

It seems there are a number of grounds at different points.
eg
[ATTACH=CONFIG]31389[/ATTACH]

I presume the desk was working ok and then something happened.
If it was dropped there could be cracks in the pcb boards.
Perhaps the grounding screws are not making good chassis contact and need removing..cleaning
and re tightening.

Great - thanks very much for that diagram. I found the grounds on the schematics Studiomaster sent me
but it's great to have them all together.

It wasn't dropped. The unit is in a large flight case and a patch bay has been
connected at the rear. I found a new short between the ground on the cable for
the mics and AUX SEND etc.
I guess this upset the works.

I'm waiting for a desoldering tool to tidy up my soldering.

Miniaturisation is all very well but I need a magnifying glass and spotlamp to see the PCB
clearly and a tiny home-made soldering tip. The LIDL solder is poor as well.

Thanks very much everyone for all the help and suggestions.
I've left it for now until the desoldering tool arrives - should have been today but EBay again........

All the best