Behringer Europower pmx660m schematics

[nosaj]

Anone have a copy of the schematics for a Behringer Europower pmx660m?

Have no output at speaker jacks, but can't quite identify the output transistors.

Thanks,
nosaj

[Enzo]

Look on the power amp module, is it a DPA300? If you cannot find the PMH660, look for the PMH1000 schematics, that also uses the DPA300. A place to start is Elektrotanya.

IRF640 and IRF9640 should be the outputs.

[mozwell]

this may be close enough
PMX1000C & PMH1000

[Enzo]

The DPA300 is included in your second link.

[nosaj]

The DPA300 is included in your second link.

It is the DPA300. Thanks for the schematics guys...

nosaj

[nosaj]

The below statement, is this acceptable to check the mosfet still on the pcb, if not what is recommended? The story on the PA is it was hooked up with 4 8 ohm cabinets ran for about 30 minutes then went silent. Lights on front appear as should, just no output.

Thanks,
nosaj

If a FET fails it most commonly give a short circuit between Source and Drain. (in power applications) You can measure the resistance between these pins. If it is lower than a MEG it is probably dead.

[Enzo]

I have to say, I don't worry what it commonly does. All I worry about is what the one in front of me does.

If your output FET shorts source to drain, then you will at least have DC on the output and most likely blow fuses.

If you have no output, connect a speaker cord to the output and see if there is a short across it. Those amps usually have a triac crowbar across the output, and if it fails short, you have no output. If that is not shorted and there is no signal or DC on the output, it is more likely the FETs are open than shorted.

Both channels lack output? Is signal getting to their inputs? Is ther a power on thump? Look at the heavy twisted wires from the power supply. Are the Main V+ and V- supplies present on them?

Is there signal coming out the mixer preamp? Apply a signal to an input channel and bring up the controls as if to play. DO you see signal on the VU meter? Connect the MAIN OUT jack to some amp and speaker. Got signal there? If the main out has no signal, there is nothing for a power amp to amplify.

You could have a bad drive IC on this digital amp, and your meter would not be able to detect that.

[nosaj]

Ok, we get output from the preamp. The PA has the nuetrik to 1/4 adapters on the back, plugged a speaker cable into A get 1.05 VDC
output B gets 27.26 VDC So channel B's crowbar triac has tripped?

Main V+53 V-53.

Looking at the fuse its a 3amp 250V slo-blo(looks like a coil instead of thing strip of metal) original label is missing to denote correct rating

manual shows 3.15amp 220V 5amp 110v doesn't specify slo or fast fuse.

So we have no output 27VDC on output B an we're not blowing fuses so that says output B FET is shorted, and we have wrong fuse. Output A FET is open? If this is correct? What possible reasons would be why it happened after playing for 30 minutes, unbalanced load?

Also maybe it does maybe it doesn't matter switch on front was set to bridge, now I know there are only 2 possible cabinet configs they have there. option 1 4 cabinets 2 per channel 8 ohms each so each channel would see 4 ohms
option 2 are 2 8 ohm peavey columns.

output B is the one with 27VDC, so I'm thinking bridge mode did this correct?

Thanks for making time for us amatuers,

Jason

[Enzo]

Crowbar shorts across the ooutput, if you have voltage there, it is not shorting across then. However, 27v on the output is not a healthy amp.

Bridge mode just connects the two channel together. Unless you go too low impedance, it won;t hurt it.

You have a volt offset on Ch A, Does that go away when a load is connected? Does ChA amplify?

ChB has a problem, find out why it is spitting out 27v. With that much DC sitting there, I do not expect ChB to amplify at this point.

I am looking at the spec sheet on page 12 of the 660/880 manual, it says:
3.15A (220-240v)/5A (120v)

[nosaj]

Neither channel amplifies at all, only way to get sound is from main or monitor output. With a load channel A goes to like .64milliVDC, but still no sound.
so +-53 volts on mains is ok?

Would this be a good op to use a signal tracer to find how far sound travels in system?

jason

[nosaj]

allright signal traced where preamp comes into amp board DPA300.
ic1 pin2 static pin4 distortion sound pin5 low vol, so for that chip low vol output ch B, no output pin 7 ch A
ic2 pins 1 and 7 good sound and vol. all other pins dead
ic3 pins1237 good sound and vol. pin 6 static all other pins dead
ic4 pins 1 and 8 good sound pin3 roaring (but it should right? for an oscillator) pin 15 roaring sound all other pins dead

It's late gotta rest now, can pull voltages tomorrow.
But I'm thinking ic2 and ic3 opamps sound is coming out both channels so I'd think ok.

ic4 output pins are toast I believe.
ic1 not sure about this one as it has a protection mode I think.

So if synpsis is correct about these IC's are they available to joe blow?

Thanks,
Jason

[Enzo]

In general you can't take readings on input pins of op amps, so if you get clean signal at pin 1 id IC2,3, then those are working. We really ought to be using a scope for anything to the right of the op amps. These are not linear amplifiers. The signals coming out pins 15 and 10 are digital, so they won't sound like your signal.

You have something at IC4-15? OK, do you have it at IC1-7? At the bases of the output FETs? Are the power rails present on the source pins of the outputs?

Is 53v proper? I have no idea, but it is enough the thing should amplify. If it were meant to be 80v, the thing would still make sound at 50. Since the filter caps for those rails are 63v types, I;'d say 53v is probably right.

Before running off for an HCA4001, make sure the rest of the circuit after that amplifies.

As to where to get them, I don't often need one, and I have enough dead amps i can steal one. You might find some at Frondelli's dbm pro services.

[nosaj]

I only have a 20mhz dual trace scope.

Ic1 pin 7 no sound.

T1 52.9 vdc .7vdc .6mvdc
T2 .6mvdc all 3 pins
D1 .05mvdc .06mvdc 52.9 vdc

T3 all under .05 mvdc
T4 27vdc all 3 pins
D2 under .05mvdc

All voltages taken with 8 ohm load. No ac voltage above .2vac no sound .

To be honest I'm feeling lost pretty sure shouldn't be any dc coming off transistors but with no ac off them id say problem is up the chain and b channel plus the ic which is only working on 1 channel other side maybe in protection mode signaling something farthr up chain from ic.

Would it be better to try and source a used dpa300 board? Its still interesting trying to understand what's going on but am not sure if I'm grasping what I should.

Thanks
Nosaj

In general you can't take readings on input pins of op amps, so if you get clean signal at pin 1 id IC2,3, then those are working. We really ought to be using a scope for anything to the right of the op amps. These are not linear amplifiers. The signals coming out pins 15 and 10 are digital, so they won't sound like your signal.

You have something at IC4-15? OK, do you have it at IC1-7? At the bases of the output FETs? Are the power rails present on the source pins of the outputs?

Is 53v proper? I have no idea, but it is enough the thing should amplify. If it were meant to be 80v, the thing would still make sound at 50. Since the filter caps for those rails are 63v types, I;'d say 53v is probably right.

Before running off for an HCA4001, make sure the rest of the circuit after that amplifies.

As to where to get them, I don't often need one, and I have enough dead amps i can steal one. You might find some at Frondelli's dbm pro services.

[Enzo]

It is an amp, it has more filtering at its output than a linear amp, because this one is digital, but it is still just an amp. The output ought not have DC on it. The output stage is a push pull, with a transistor to either main V rail. SO T1 has 53v on one pin, look at the schematic, the source pin of T1 connects to +VCC, it does it through that 0.1 ohm resistor R7. Now you report all three pins of T2 at essentially zero, no -53v. Well, -VCC, the -53v, needs to come through the 0.1 ohm resistor R1. Is R1 open?

If the main voltage rails do not get to the output transistors, they cannot control it on through to the speaker to make sound. These may be MOSFETs instead of bipolar transistors, and the amp may be digital rather than linear, but like any amp, its job is to control the power supply to feed it to the speakers to make sound. And that is exactly what a tube amp does too.

Would you be better off replacing the amp module? Be my guest. I am happy to try and assist in repair, but up to you if you are drowning in the effort and would rather bail. I have no idea what new DPA300 boards sell for, nor how many used ones are available. AT least replacing them will be quick.

[nosaj]

Ok I found some time to get back to the PA..Here's what I found. R1 is open. So I went ahead an measured the other resistors. I used a Simpson 260.

r1 open, r3 900ohm, r8 measures 1000 ohm then rises to 2000 ohm, r11 1000ohm, r12 1000 ohm, r13 1000 ohm, r14 1000ohm, r17 600ohm, r18 400ohm, r23 800ohm, r24 400ohm.

So it looks like we've got some resistors to replace. Is there anything else I should before replacing anything.

Also why do R1 and a few of the other have heatshrink on them, is just for insulation?

Thanks,
Jason

I'm not ready to bail yet. Just having some issues looking at the schematic and determining which way the circuit flows sometimes it seems like a garden maze.