stereo out problem

[ReRibbon]

I don't want to step on ln76d's toes - he has been putting in the hard yard here!

Smoking resistors on the power rail may indicate a short somewhere. I could be wrong, but they appear to have used bear single core wire for the bus bars.

There's no shorts here is there?(that is some bus wire touching others?) Its hard to tell from the picture but they look like they are getting pretty close!

Yes he has! is greatly appreciated!

The bus bars are exposed metal, but no crossing/touching is happening.

No shorts that i can find. Will go through it all again. Horseshoes and hand grenades?

 

[ReRibbon]

Ok. Prior to swapping thr resistors for jumpers, i tried unhooking the R Aux OPT to see if this connection was creating the hum (60 hz). It was not and is still currently  unhooked.
The resistors started to smolder again, so unplugged.

I then swapped the resistors for jumpers. The smoldering stopped, but nothing else changed. I checked to see if the op amps on the R Master channel were hot, and no they weren't. I checked the VDC and they were at +17.22 and -16.82.

Tried to check VDC at the point where the PSU cable meets the mixer to power it. While the common probe on the meter was clipped to ground of the chassis,  I touched the + probe to the - rail and it read -16.82. I then touched the probe to the + rail and ....... SPARK! I turned it off immediately.

Could the + rail channel be somehow connected to ground?; defeating / shorting the Right master out audio path?

If so, for what reason had there been no sparks before?

 

[ln76d]

Check did you put correct orientationof capacitors after recapping.
Check electrolytics with the "beeper" (powered off unit). 
Check with the beeper  points to each other where's -V, +V and GND. You can start from opamp powering pins.
Check did you connected properly power rails (in proper place on board tracks - didn't you swapped -V with GND)
If these are ok change opamps.

 

[ReRibbon]

Check did you put correct orientationof capacitors after recapping.
Check electrolytics with the "beeper" (powered off unit). 
Check with the beeper  points to each other where's -V, +V and GND. You can start from opamp powering pins.
Check did you connected properly power rails (in proper place on board tracks - didn't you swapped -V with GND)
If these are ok change opamps.

Yes, the caps are in the correct direction.

A beep is good I assume because it would show continuity(?).

I'll look again to see if anything is swapped backwards.  Hadn't found anything so far.

Ok. Back to work.
Thanks

 

[ln76d]

A beep is good I assume because it would show continuity(?).

If your multimeter do the  beep sound, it will be continuity.
Check also -V, +V, GND to enclousure continuity.

See ya tommorow  ;D

 

[ReRibbon]

Ok.
This will be a stupid question. Is a beep for continuity good or bad? What if no beep, but the meter still reads something? 
By checking for this beep what am I looking for?

 

[ln76d]

Ok.
This will be a stupid question. Is a beep for continuity good or bad? What if no beep, but the meter still reads something? 
By checking for this beep what am I looking for?

Maybe not stupid, but hard question

Usual meters in diode testing mode/beeper will show you "something", because in  the circuits everything is connected  to each other in some way.
There's also other option - is it your multimeter working properly?
I had one multimeter, which had some issues  with inner connections, usual i had to press hard the test leads to get proper continuity test - a "beep". Without pressing it was reading something or even not reading anything when it should make the sound.
Test your multimeter on some obvious things, is it beeping always when it should - few times metal enclousure for example.

With beeping you are searching is there a short in the circuit.
When you check capacitor if it beeps it's bad.
With the points mentioned earlier post your results and we will check is it good or is it bad.

 

[PRR]

Continuity is good for circuits which "can only be" open or closed.

Trailer lights. Either the connection is good, or it isn't.

For electronics, LOOK at the numbers and use a brain.

 

[ln76d]

Continuity is good for circuits which "can only be" open or closed.

Trailer lights. Either the connection is good, or it isn't.

For electronics, LOOK at the numbers and use a brain.

It's a hard case a little bit, so i think for the start ReRibbon could check with simple continuity test.
Then we will see for what we will be able to use our brains

 

[ReRibbon]

I started to check all the caps and since there isnt any form of schematic to anyone to look at, decided to give it a go at making one'ish'.

I traced alt least  99% of everything on each channel. Some stuff was looping around and I know i had written it down already on another part of my notes, so i passed it over. Redistor / cap values are available if needed. Just ask. I have not gotten to the Master stereo bus boards yet. Because I have no way to competently draw anything like this out, and I don't have a program to type all this stuff into, it will have to do for now...

I have taken photos of my notes and will upload them momentarily.
If anyone takes the time to read through this stuff, I tried to use arrows under the sentences to show direction of the components and how the channel is laid out.

In regards to checking the caps and things, I'll get to it tomorrow.

 

[ReRibbon]

The photos  were too large so Ive uploaded them to dropbox.

https://www.dropbox.com/sh/x6yck1aqyoyuu0u/AABrFpKsQoU4oDcGkqjts0VHa?dl=0

 

[ReRibbon]

Update:

Haven't gotten back into the mixer yet. Am going to later today.
I am wondering, would it be possible to just hook up the audio OPT(s) to the VU meters?