Behringer Europower PMP1280S Mixer

[MARSHALL BUSTER]

Hello guys i hope your all keeping well.

Im just looking for some info from the schematic for the PMP1280S please if you can?

I have just had one droped off and it seems to be missing some parts from one of the boards!

The board number is BF0496A, and the components numbers are C52 and C53. Thery are missing from the board and the solder looks like they sould be there so i dont have the old to compair to a replacement. Looks as though a glass of beer's been spilt since there is a dry residue on the board. Someone has been in here before to see if they could fix it but i dont know why they have removed the components. Cap number C17 is also blown, it has a 'lumpy' top and melted plastic cover so that will need replacing too but before that i need to know what components are missing to order it all at the same time. If there are any other points you think i should know about, or checks i should make before replacing the components and powering up the machine then please pass them on to me.

Thanks for your help and take care.

[Enzo]

What board is the BF0496? Powr suppy? Mixer? AMp? AC input? Speaker connector board?

[mozwell]

I hope this helps
C52, C53 are on page 13, in the power supply, 1u 100V drawing location A6, C17 is just to the left, 4700u 100v
I woudl check the diodes D6 & D9, unplug headers X3 and X5, adn see if all the power supplies comes up ok, maybe use a light bulb limiter for the first power up.
Check the other diodes in the power supply & the primary switching transistors T3 & T4 (with mains off, of course).

[Enzo]

The boards are wave soldered underneath and reflowed same side, so all the holes/pads will be soldered whether a part was there or not.

That is the power supply board, and is an SPS1000 supply.

Those two parts are optional. The SPS1000 I have in front of me does not have them installed either. They are small surface mount caps on the underside.

I also am not convinced that was a beer spill. You would have a very blown up board if beer ran across it. When boards are made, the wash them in something very much like a dishwasher. They do this to remove solder flux and other contaminents. A lot of these wind up with a white residue after that. Perhaps they should have used some Calgon Beads....

I suspect that is what you are seeing.

C17 with bulging top? Maybe. Those four large caps along the board edge are plain old aluminum cans, with plastic wrap shrunk around them. To cover the end there is a plastic disc sitting there, held in place by the shrink wrap. SOmetimes that plastic disc domes up just from warping in the heat. The cap under it is fine. If your cap is acutally bulged, it must be replaced, but before pulling it, slit the plastic wrap and pop the end plastic disc out. If it was pushed up by a bulging metal can, the part is history, but if the luminum can underneath is stil flat, the cap is probably OK, and the bulge is nothing.

Since ther are two of those 4700uf/100v caps on each rail, if only one is bad, you can remove it, and the system will work without it, at least well enough to troubleshoot anything else.

But also be aware that these SMPSs work very hard at protecting themselves, and will shut down with the detection of most any fault. For examp,le a blown power amp will cause the power supply to shut down.

Is your power amp the dual one, HCA2400? The power supply has two three pin connectors in the corner for the power amp, one for each channel. Three heavy wires for each. You may unplug them AND also the small 6-pin connector to the power amp, then you can fire up the system. If the thing now comes up and powers the mixer section, the power supply may be OK, and the power amp blown. That small 6-pin connector carries the +/-15v to the power amp, but it also detects the lack of high power voltage ther, so you must unplug it in addition to the high voltage wires if you want to operate the supply without the power amp.

I suggest you do that to determine if the power supply reeally has a problem or is just hibernating.

Mozwell, your idea is valid, but he cannot pull only X3 and X5. The power supply won't fire unless he also disconnects X6 from the power amp.

WARNING: by the way, there are no bleeders on the high voltage supplies, so if you pull off X3 and X5, those two supplies will stay charged up to like 80 volts for a LONG time. If you want to work in this board, once power is removed, you must discharge these supplies with a resistor, otherwise you can get a dangerous shock.

I highly suggest you look over the power amp and check for shorted output transistors in its heat sink. At this point I am wagering your power supply is probably good.

[MARSHALL BUSTER]

Thanks Enzo for your detailed explaination & Mozwell thanks for the 'pdf' i will get on to that later today and post the outcome.
Thanks guys

[MARSHALL BUSTER]

Ok so i i'v disconected X3 & X5 but left X6 as its soldered in place and yes she powered up the mixer, so Enzo and Moswell your absolutely right power suply is good!! Iv removed and checked D6 & D9 as sugested and both apear to be fine. T3 & T4 also checked ok.

I noticed when i powered up that all LED's on the level meter for the main left on the front of the mixer was up in the red, all LED's lit up!?! Could this be causing the SMPS to trip out???? and maybe the power board is ok and the problem lies at the mixer???? Just to remind you i did not disconect X6 as you sugested Enzo, im just thinking would that mean the power board is ok. Im out of time today on this one so i may strip the mixer tomorrow to see whats going on in there!!

Any ideas??
Thanks again keep up the good work

[Enzo]

X6 is soldered in, yes, you unplug those wires from the other end, at the power amp end.

If the left VU meter is all lit, either the circuit that drives it is faulty, or that channel has a dead IC in the signal path. Look for an op amp with DC on an output pin.

If ALL the LEDs are lit across the board, and I mean every peak light etc, then that usually means a missing 17v rail. If ONLY the VU meter is all lit, that won;t be the case.

The SMPS has no way of knowing the mixer section has a maxed out VU.

Remember to totally discharge those high voltage supplies before re-connecting them. I'm serious.

You have two high voltage power cables, one per power amp channel. Here is a simple procedure. You have red, blue, and what, yellow? The center one is ground. Measure to either red or blue for shorted to the ground pin in the center. If you find one side shorted, then that amp channel is blown.

I have not yet seen anything to make me think that your trouble is anything but a blown power amp.

[MARSHALL BUSTER]

""""Remember to totally discharge those high voltage supplies before re-connecting them. I'm serious.""""

No worries my friend, i sorted that when i read your advice, I discharged them with a domestic 240v light bulb and no joke it lite up good for 2 seconds before dimming away, then finished off with 12v bulb and a resistor. So safety is another good thing i learned from you on this one, Thakyou.

Ok im going to deal with the level meter later on and sort the power amp section first.

Blue, red, black the wires black being centre!!....
black & blue: Meter bleeps for a second then rises steady to measure 376mv on both X3 & X5

black & red: Meter rises steady to 'infinite' i think is corect term, on both X3 & X5

[Enzo]

We are doing this on the wires, and they are n ot connected to the SMPS, right?

Checking from black to red, and black to blue, but also, don;t forget to check blue to red directly. They can be shorted together without shorting to ground.

And while we are at it, try this. The red and blue wires are the main hiogh voltage power rails for the power amp. Measure resistance from the hot wire - the non gournd wire anyway - of the speaker connections. Are there not a twisted pair of red and black from the power amp board over to the two speakon connectors? See if that red speaker wire is shorted to either blue or red power wire. If an output transistor shorts, it will short the speaker wire to the powr rail.

I don't know if I am thinking the right product here. Is this a molded black plastic thing, with a large round area scooped out of one end for a handle there? Take off the reap panel and the SMPS and power amp are down in a sort of steel box? Like the PMH880? I swear, all these I have ever had to work on, I cold not for the life of me figure out a reasonable and convenient way to get the damned things apart. Screw heads hangiong up on the edge of the tight opening, etc.

[MARSHALL BUSTER]

I don't know if I am thinking the right product here. Is this a molded black plastic thing, with a large round area scooped out of one end for a handle there? Take off the reap panel and the SMPS and power amp are down in a sort of steel box? Like the PMH880? I swear, all these I have ever had to work on, I cold not for the life of me figure out a reasonable and convenient way to get the damned things apart. Screw heads hangiong up on the edge of the tight opening, etc.[/QUOTE]


Yip you got the right product there, a big black molded thing indeed. I also have no idea how the thing comes apart hence i'm not yet looking at the level meter problem just yet!!!. Would serve life better as a bin liner if you ask me hehehe. Iv also got a pmx2000 and a Peavey XR684F and its so much a better design to work on.

Ok no, i had the wires still conected to SMPS

I'l be back later

[MARSHALL BUSTER]

I have been testing and testing and still coming up with the same results!!. So i reconected all cables and put the amp all back together and it now powers up and i can hear sound in the speakers but no out put from the mixer!?! so i dont know if there was a dry solder joint involved or what.

The mixer is not sending a signal to the power amp and the FX section is not illuminated. The left signal level meter is still up in the red and all other Led's seem to be doing what they should. When i conect a mic to a chanel input, the MONITOR level meter reacts to taping the mic but nothing on the MAIN level meters just the left lit up fully and no activity on the right.
Im now about to investigate further into what Enzo mentioned in the earlier thread about the mixer..

A few hours later......

Ok well i now have the amp out of its casing and all conected up on bench and this is what i have....

1.All the mixer parts including FX seem to work fine now (dont ask how cause i dont know hahaha)

2.In MONO i have perfect music from output A and NO sound from output B at all.

3.Output B is giving out around 64vdc but no buzz through speakers???

4.In stereo i have No music from output A or B but can hear the hiss of power going to the speakers.

5.The left chanel meter if still up in the red and never moves.

My newest thought is if whomever has been in here before may have put some wires to the incorect conector?? i have had this before on a Marshall avt275 and was seeing similar problems. The output boards were conected wrong in that case and giving out 43vdc and a huge buzz.

But i can't get my head around the schematic, its not telling me where 'for example' the big wire conectors with the blue black and red wires should go, ie X3 or X5 or would it make any diference if the conector for X3 was on X5 and vise versa???? I hope im explaining this clearly enough im doing my best

On my amp The conector at X3 on power board is going to X2 X4 X6 on the amp board.

The conector at X5 on power board is going to X1 X3 X5 on the amp board. Do they sound right?

[km6xz]

I don't want to interfere with the ongoing instructions but notice you mention 64vdc on the output of B but no hum from the speaker. If you are new to amp repair you probably just learned rule #1, never connect a load, particularly a speaker worth more than $0.05 to a solid state amp until you have proven it to be stable with no offset or oscillations. Since there is a obvious problems with the mixer, focus on that first and disconnect the power amp entirely until the mixer is operating perfectly as intended. It is unlikely for multiple sections of a mixer/amp to fail at the same time so fix the mixer first and you might find that there is no problem with the power amp when the mixer is back in shape. The slow increase in meter level sounds like a DC offset between stages in that channel of the mixer. Do you have an oscilloscope which will allow signal tracing? Have you looked at all the line outputs of the mixer to see where the signal on that second output so screwy, for example Fx send and monitor? The meter segment drivers are DC coupled so any leakage in the drive, say, Main Left out will be reflected there in a meter reading. You have enough external taps into various places in the signal chain to see where normal signal is still present and where there is an offset. The effects sends, the tape out, monitor out etc all give indications of where the problem is if you look at them with the scope in DC coupling
Good luck

[MARSHALL BUSTER]

Hi Km6xz
Please your not interfering im very greatful for your input to the problem.
Haha rule #1 learned along time ago. My brother was the electronics brain in my family sadly i hes not with us anymore to advise me, so all i have is what i learned from him, a multimeter and some of my own expirence!!!

What iv found is 14.71vdc at the main left output of the mixer, the right reads -1.55vdc. Thats the only jack showing an unexpeted reading! all line inputs are working normal through the Fx and Eq. But i think the left and right signals are mixing (like mono input!) , when i unplug the left input the sound looses volume on both signals rather than just that relevant side!!! same if i unplug right input.

My tools are limited i do not have an oscilloscope it been on my christmas list for a while now maybe this year