stereo out problem

[ReRibbon]

Hello,

Im having two issues on this boards' master out / right channel and the right channels' aux send OPT. Before opening up, all that stuff worked great. Now only the Left channel works (for both Aux and Master outs).
So,
1. The Aux Right OPT became disconnected at its primary from the circuit board (the point where it receives the audio signal). It's secondary is still attached to the XLR aux out. Additionally,  the Main Right side OPT, has not been changed whatsoever.

Obviously this breaks the signal to the Aux out. It is routed after the Main Right OPT in signal path, so could this possibly defeat the entire right channel?

How can I locate the appropriate points to reconnect the Aux Right OPT primary? I've looked at the Left channel points, but the board is laid out differently.

2. If that doesn't in fact create the overall right channel failure, what else could? I've checked for solder bridges and all that. It's clean as far as I can tell. I have a Fluke 77 to work with as well.

Thanks for any help in advance.

 

[isophase]

what type of board is it? what model?
why did you open it in the first place?

 

[ReRibbon]

It's an obscure British thing from 1982 called a location mixer. A great sounding 8x2  board when up and running. Seems to be a Neve or Toft type clone. It's git Belclere xformers as well as stepped gain eq controls.
It needed a recap so that's why it got opened. When I leaned it  over, the Aux right OPT primary wires got pulled off, breaking the wire beneath the solder and leaving me with only the coated portion of the wires. No point of origin is visible.

Because there are 2 aux sends (and all panning is done on each track), i thought maybe if I connected the primaries of both Aux R and L OPT to where the (still intact L Aux OPT) primary was, it wiuld make the connection.  After doing that, no audio passes at all. Phase?
Will disconnect this last step and see if it goes back to how it was.

No schematic is available.

 

[Pip]

PIX PLEASE

 

[ReRibbon]

What would you like to see?

 

[ln76d]

What would you like to see?

Everything, what you need to repair...
Didn't you learned from previous topic, that if you place more pictures, videos etc. that there is a chance to make some progress?
We are not clairvoyants!

 

[ReRibbon]

Hahahah! Howve you been my friend?

Let me make a movie.

 

[ln76d]

Thanks, fine, little bit tired
Hows the channels working?
Tommorow i will watch the movie

Goodnight!

 

[ReRibbon]

Movie is uploading. Will be a little bit.

 

[jwhmca]

It might be laid out differently, but certainly it will be laid out the same functionally.

The OT primary on the working (left) side comes off______________?

I betcha the right comes off the same type component... Maybe a large cap?

 

[ReRibbon]

After doing this step, the right side still did not pass audio. Additionally,  there is a 60hz hum on the left master channel output now. I will remove the soldering points of the R Aux OPT primary and see if the hum goes away.

Heres the video. Thanks in advance.
http://youtu.be/eJmL0bl-4fQ

 

[ln76d]

Did you changed opamp in the path?
If yes - there could be similar issue with current limiting resistors.
If not - original opamp could be damaged after previous issues.
Check first is there any opamp hot like before

 

[ReRibbon]

No, I did not change any opamps in the master bus section.

Just turned it on for a minute. A resistor on the right side master out started to smoke. It appears that this set of resistors has done this before, as they are not original and there are  heat marks underneath both of them. They will need to be replaced. They are in direct line with where the power cable comes from the PSU to power the board and are in the Positive Negative paths accordingly.
The resistor on the right is in the path in between the Positive from PSU and pin 8 ofthe op amp right behing the stereo monitor level pot.
the resistor on the lef is in between the negative from the PSU and splits its other pin to pin 4 of that right side 741 op amp..as well as to the same pin of another 741 op amp (closest to the AC power plug. The resistor  also splits off to pin one of the tlo72 op amp behind the stereo monitor out.
None were hot. Only the resistor.

 

[ln76d]

If i understand it correctly, those are current limiting resistors.
Put the jumpers instead, like on channel boards.
Ewentually make a photo, which was where.
If it still doesn't work replace opamp.

 

[ReRibbon]

Would replacing resistors with jumpers affect the amount of voltage or current that is going to these op amps? They are the original ones and haven't been messed with.

Here's a vid and a pic of the resistorsand where they  go. as pictured,  the resistor on the left in the photo is the one that i referred to as on the right in previous post.

As pictured, the one on the right reads 28 ohms. The left one reads 22.8 ohms. Ill assume that its the one that smoked.

http://youtu.be/HoFG2MG8cMs

 

[Humner]

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!

 

[ln76d]

Sa

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!

Don't worry 

Same problem was on channel boards.
If there would be a short much more would be destroyed,

Would replacing resistors with jumpers affect the amount of voltage or current that is going to these op amps? They are the original ones and haven't been messed with.

Here's a vid and a pic of the resistorsand where they  go. as pictured,  the resistor on the left in the photo is the one that i referred to as on the right in previous post.

As pictured, the one on the right reads 28 ohms. The left one reads 22.8 ohms. Ill assume that its the one that smoked.

http://youtu.be/HoFG2MG8cMs

Check each opamp datasheet for correct pinout, if those resistors are in psu patch to opamp - put jumpers.
Voltage would be same. Each opamp will get current which it need.

 

[ReRibbon]

What does patch mean please? Maybe path? Maybe another thing?

 

[ln76d]

Should be path not patch...

 

[ReRibbon]

Ok, will do tomorrow and update. Thank you for your help.