Behringer PMP960M

[Jazz P Bass]

[QUOTE=Enzo;234637]
You have the schematic, so look. QUOTE]
Umm.
Lowell, if you have the schematic, can you please post it so we can see what is going on?
Thanks
John

[lowell]

NOT sure if Behringer'd be ok w that. Don't have their policy papers with me now. Enzo?

[Enzo]

Policy is that as a service center I am not allowed to distribute diagrams. I was not aware if you had become one of their service centers, Lowell. I have no control over nor responsibility for what anyone else puts on the internet. I have never seen Behr give out any drawings, but if they sent one to you, I'd assume they asked for it not to be spread. If you found it online somewhere or someone else sent it to you, then I'd guess it would be up to you.

I'd imagine if Behringer became aware some drawing was posted in some forum, they could ask that forum to remove the post.

[lowell]

Okay so just got back from Maui. I'm gonna cut my losses w/ this PA head. I've already spent weeks on it and am not going to devote anymore valuable time to it. I may pickup where I left of when the next one comes in. I prefer this customer exchange it for a new one w/ Behringer. I have many more amps that await repairs. Thanks for the help.

[francuccino]

PMP960m Now Blowing fuses

HArd to say. It sounds like the thing is trying to start up but quickly kills itself. The most common reason for that in my experience is shorted rectifiers on the secondary. We checked those little diodes, but don;t overlook the larger ones on the heat sink for the main V+ and V- to the power amp. But other stuff can also do that.

There are more of those diodes than the few I listed. Check every damn one of them on the board.

I suspect your main switchers are OK or I'd expect blowing fuses. I could be wrong.


You have the schematic, so look. There are two switching circuits on this. The mains is rectified and filtered, then the DCV-H is fed down to U2 which switches all the stuff in the lower left quadrant through T3. All that is the low voltage supplies. Note in the center of that the little +16v rail, from D27. Then there is a second switching circuit in the upper right quadrant. Instead of a little thing like U2, this high powered switcher uses U5 to control Q1,Q2, power transistors working through T2. Note that U5 runs off that little 16v rail from the low voltage section. In other words, the high power high voltage supplies won;t come on until the low voltage supplies come up.

SO hold a scope probe next to T3 and see if it is cycling through moments of trying to pulse. And remember that "ground" on the primary side of these suplies is NOT earth ground. And try the same thing next to T2, just to see.

The secondary outputs are referenced to ground, but scope them and see if little pulses show up each time the SMPS tries to fire.

A friend said he smelled burned components in his PMP960M so I said I would check it out. The fuse was not blown when I got it. I found the PSU18 with U2, a 765RT, totally burned, I also found ZD1 shorted and a lot of charred components nearby. I replaced the U2 and guessed the ZD was 18v. Now at power up it blows the fuse. I will check the rails and diodes again, but without a schematic I am flying blind here. Can you give me the value for ZD1 and any help trying to figure what happened to this SMPS, or is it a total loss? Thanks

[Jazz P Bass]

I have given up trying to repair these amps.

You could always use it as a mixer.