Behringer PMP1000 circuits / experience?

[Brian Swatton]

I've got one of these in blowing fuses. When I first checked, there appeared to be a short on the power rails to the amplifier.

However, after dismantling, I can't measure this now, but can see that there has been a blow up in the SMPS, between C4 (a 1kv cap) and the device opposite (top left of PCB as viewed from front). Without going much further I'm guessing it's around the primary switching.



It's always tough finding Behringer drawings, but if anyone could point me at something I'd be grateful. I used to be a test engineer for an SMPS mfr. so I'm prepared to do it, but only with a drawing. Behringer PCB's are always pretty difficult to track trace I find.

I'd welcome thoughts from anyone who's repaired one before. These units are not that expensive for what they do, so I don't want to take it on if it's likely to be a big problem. I'm a bit concerned there could be issues with the amp stages too, though nothing indicates that so far.

[Enzo]

So please do check the power amplifiers for shorted outputs. That will surely appear at the SMPS if left connected.

WHICH SMPS board is in the unit? OK< doing some looing, it appears to be the SPS400 board. The PMP1000 appears to be the same as the PMH1000

For people not affiliated with Behringer, the first place to look for their schematics is Elektrotanya. There I see they have the SPS400 as a separate schematic, and the4y also have the PMH1000 drawings.

[Brian Swatton]

Thanks Enzo,

When I thought I was looking for a short in the amp, I did have that module out and check the FETs. No shorts found, and that was when I realised the supply short had disappeared too. It was neither at the amp or PSU. Then I spotted the burn mark in the PSU, which hadn't been obvious at first.

Thanks again, I'll check out Elektrotanya

Not sure if that will be today. I've hit my half century on the planet and am tempted not do do any work

Cheers

[Brian Swatton]

Just in case anyone is interested...

The customer's report was : One channel blew and the fuse went, so we changed the fuse (#!*?). The other worked for a while, then the fuse blew again.

What actually happened:
The primary snubber cap C4 in the PS had destroyed itself. Apart from lots of soot/smoke nothing else appeared to be wrong. The amplifiers looked fine too, but, the faston connectors to the output connector PCB were looser than anything I've ever seen, I seriously doubt they were connecting, if touching at all.

After tightening those, cleaning the damage and changing C4 I was able to power up without any problems. It's sitting on the bench soak testing now. My feeling is that intermittent loading is what probably caused the PS failure.

Thanks Enzo for the Elektrotanya link, I'd forgotten about them - in the bookmarks now.

[greenmeanh1]

Hey guys, its been a while since i have been to the forum.
i come searching for info on the Behringer PMP1000 mixer and found this thread.
I cant find the schematics for this thing and there is a couple of parts i need to identify.

Problem summary. Power unit on and it just makes clicking sound coming from inside the amp section but nothing out the speakers..
All mixer inputs and outputs appear to be receiving and sending signal. Just no sound.

Open up the unit and measure the voltages off the pwr supply. I get 5v,steady, 48v steady 15+steady but the -15 was jumping all over in sync with clicking sound.
Remove all wiring between amp board and power supply and test power supply again. All voltage outputs stable now, other than the -15v was more like -18v .
I did notice that R10 and R11 which feed the +- power to the amp board were burnt up so bad i cant get the color codes. Any ideas what value R10 & R11 might be..

Open up the amp section, test the 6 transistors and i found one shorted IFR640n so likely that is the problem, going to see if i have something around that will work for that.
Aside from that, everything else seems to check out as far as in circuit testing of parts goes.

So i guess i just really need the values for R10 and R11 in the SPS400 power supply unit..Hopefully someone knows off hand. Thanks

.

[dmeek]

R10 and R11 are both 2K, here is the schematic:

SPS400 psu.pdf