Behringer Europower PMP6000 - Identify transformer specs

[bmandle]

My son and I acquired one of these boards for $25 that wasn't working, as a project for him to get more familiar with electronics. It's been great teaching him about all of the different components and after testing all of the diodes on the power supply board he found the faulty one, D6! After soldering a new one on the board powered up beautifully and all of the passive sound outputs worked great. Unfortunately, the powered outs only push out a scratchy low volume. We figured this was probably due to the amp board not getting proper power so after testing our way down the path we ended up back on the SMPSU29 power supply board at the TR4 transformer. At first glance it looked ok but upon further inspection it appears to have a slight melted deformity in the plastic on top. We confirmed that it is receiving the approx. 170v going into it, but there is no power being output and it's cool to the touch when the rest of the board is powered on. Since we have the schematic we also saw that the fan power comes off this transformer as well and they aren't operational either. So we're pretty sure the transformer is at fault and needs to be replaced. Unfortunately, the schematic doesn't have the transformer values and we've spent two days trying to identify online what the specs are so we can get a replacement. Any help would be most appreciated. Thanks, and sorry for the long-winded post!

-brian

[Enzo]

Anything possible, but I doubt the transformer is faulty. I've never encountered one in an SMPS.


DANGER: PLEASE be aware the mains are directly rectified and filtered. This results in +170vDC and -170vDC on the primary side circuits. In fact the controller IC runs on like 12v or 5v - I forget which - but that is NOT referenced to earth. For the primary side, the "ground" is really the -170v rail. DO NOT clamp your scope ground clip to "ground" there. If you do, junior learns about fire.

Also, SMPS operate at high frequency. You cannot measure the AC in those transformers with a meter. They run at 50kHz, 100kHz, or higher.

The power amps run, if I recall, at about +/-84vDC. And if you run teh SMPS with the power amp disconnected, those 80v supplies will hold a charge a good long time. A solid uncomfortable poke, 80v.

[bmandle]

Thanks Enzo, I've been very careful with identifying the danger areas and haven't let him do anything while the board was on, and the caps were still charged. I think at this point we'll take it to a local tech we just found out about and let him assess. And if the repair is too much than my kid will have a decent $25 passive mixer for his band!

Thanks for the reply!

-b

[Enzo]

I used to be a Behringer service center. I do think those are pretty nice mixers, especially for like a garage band. Sure beats what I toured with in the 1970s. I wound up with a number of them, and blown power amps was the main failure - things like a bad slider or blown IC somewher were easily fixed. I retired and instead of doing repairs to those power amps, I just removed said amps and rewired a couple jacks as line outs, and as you suggest, I had passive mixers with good features.