Behringer PMX2000 Mixer to PA connection issues

[soundguruman]

Probably a shorted op amp
You can feel the op amps after the unit has been on a while and see if one is getting hot.

[Jazz P Bass]

Probably a shorted op amp
You can feel the op amps after the unit has been on a while and see if one is getting hot.

Just to clarify.
The problem, as stated by the OP, is NOT in the opamp supply.
There is a specific winding & voltage regulators for those voltages.
This problem is in the output section.
+15 & -15, as labeled on the schematic, are only for the output circuit.
They have there own windings.

[Enzo]

First suspect is the zener diode itself.

[Jazz P Bass]

That would be D20.
Oops. I missed that.

[Resh]

I checked T3 and T11 (the corresponding component on the left channel) and they both showed a voltage of 8.8v while T4 was showing the correct 15V. I'm not sure how to check them individually to see if they are the issue but physically they don't appear to be damaged. I swapped D20 and D21 and there was no change so those diodes are fine. I'll try D19 and C7, both dont appear damaged but I'll pull them out and see.

EDIT: I just checked D19 and D49 and they are both fine.

EDIT 2: I turned on the unit for a few minutes to check things out and found that T18 and T19 were hot. I'm not sure what these are used for but should they be getting that hot? They both have around 60V across them.

[Resh]

I have FINALLY figured out the issue. I was testing out the unit with some music playing through it and discovered that when I moved the wires coming from the transformer the music would fade in and out. I had checked the voltages and they were all fine but I'm guessing it wasn't putting out enough current? Anyways, this leaves me in a bit of a situation, are transformers easy to get a hold of or should I cut my losses and just get a new PA?

[J M Fahey]

I have FINALLY figured out the issue. I was testing out the unit with some music playing through it and discovered that when I moved the wires coming from the transformer the music would fade in and out. I had checked the voltages and they were all fine but I'm guessing it wasn't putting out enough current? Anyways, this leaves me in a bit of a situation, are transformers easy to get a hold of or should I cut my losses and just get a new PA?

Don't get you.
If moving the wires makes music fade in and out, check why.
Why *now* that you found something affecting the failure you want to give up?
C'mon, you are quite close now, walk the last few yards.
Good luck.

[Resh]

I would love to keep going, but I don't know how to proceed. The issue is on the transformer side of things. There's some burn marks on the side of it so I'm guessing something is loose or shorting out inside of i I don't know the first thing about them, can you just cut them open without screwing everything up inside? I was under the impression a bad transformer was something to be replaced, not fixed, but I'm more than open to suggestions!

[g1]

The transformer wires connect to the circuit board. It is those connections you want to check. Chances are you just need to to some resoldering.
It could also be that moving the wires is flexing the board a little, and the bad connections could be elsewhere.

[J M Fahey]

If itīs really inside the transformer, itīs beyond repair for most except the diehard with no other options, but I much mistrust the connector on "the other end" of said wires.
Check it.
*Worst* case, cut the wires one by one close to the connector and solder them straight to the solder pads on the lower side of the board.
Be careful, work with good light, glasses if you need them, and avoid shorting one pad or wire to the next one with too much solder.
But first with long nose pliers move wires entering the connector one by one, maybe thereīs some bad contact there.
Post a picture of the connector.

[Resh]

I guess I spoke too soon. I tried to recreate the situation and I couldn't. No matter how much I moved the cable nothing. I thought maybe it had been the ribbon cable I was bumping into before and since there seems to be some burn marks at one of the ends. I took out the ribbon cable all together and soldered in wires to each hole connecting the two. That didn't change anything. Just for kicks I tried disconnecting pins 1 and 3, the signal wires that connect the PA to the mixer, and the music still came through just as it always did, there was no change. I'm assuming that shouldn't happen. I'm guessing that means that the signal is leaking through somewhere else?

Another thing I found is that if I check both sides of D3 or D4 with the meter set as an owmmeter while the units is on the music gets louder. I also rechecked the schematics and I'm only showing 14.5V where it should be 17.

[Markizz]

+ 100500

+100500 dudes

[J M Fahey]

^^^^^^^^^^^^^^^^^^^^^^
Always nice helping you spambots.
At your service.