Behringer PMP3000 No Audio output Help

[wolfpup]

Hi, Iv been trying to fix this for about 2 weeks now, the PMP3000 powers up i can get sound from headphones all inputs work, it has 2 problems the LED readout for FX is missing segments (not to stressed about that) and no Amp output

the amp in my pmp3000 is a HCA2400 and i have a question, the amp it self was not burned up and my voltages seem ok , but no output, the other day i flipped it on to do some more testing and it played for like 3 mins when i had it on the test bench i could not find any voltage differences!! maybe a bad opamp ?? also on connector 6P pin 6 i have -14V and its labeled as OFF should that be a positive voltage ? the other pins on that connector 6P are

(p1) +11.8V
(p2) Agnd
(p3) -12V
(p4) Pos+ -14V
(p5) Pos- -20V
(p6) OFF -14V

the +12V line is a little low i have changed out all regulators in the power supply already but still 11.8V dont know if that's enough to make the amp fail to power on what do you think ?



note mixer board settings are correct, i can trace audio directly to the amp its making it there with out any problems.

[glebert]

Does the input signal come in on this connector? Kinda curious what Pos + and - are, and why they are both fairly large negative voltages.

Here is the schematic from the thread on the PMP1280. I would start by measuring the supply and reference voltages at the digital IC and the V +/- (high voltage rail) points.

[Enzo]

The 6-pin connector has the LV power rails and a sense line to shut down the SMPS in a fault. There are separate signal input connectors.

On the 6-pin:
1. +12
2. GND
3. -12
4. Thermistor on heat sink
5. Other end of thermistor.
6. SHutdown signal from SMPS

The thermistor is connected to the fan drive in the SMPS - the SPS1000. The POS+ and POS- are wired into the fan drive, which runs on a -21v supply, so finding those negative voltages there looks fine to me.


Seems to me the two channels of the HCA are connected to small circuit boards for each Speakon connector. I believe there is a crowbar triac on each. If one of the triacs shorts, no sound. A simple test is to pull the wires off the Speakon board and use clip wires to connect your speaker.

I believe negative is the operating condition on the OFF line.

[wolfpup]

Ok i checked the output wires from amp before the triac board , i used a signal tracer i get just a hisss sound out of it but no audio. so i have some kinda amp problem ill have to try and follow the audio signal in and see where it go's missing.


rail voltages are all good , the Digital IC you talking about IC5 ? pin 15 +11.8 pin 18 -12 pin 10 is -5V pin 3 is +5V , i also note that ic is warm but not hot enough to burn my finger.

oh ill check the speakon board right away. Thanks for the info ill report back soon

[stelioskoz]

wolfpup did you found any solution? i have the same problem . when i start it i have no sound but after 5-10 minutes the amplifier works. if i shut down and start it again then it starts and work after a few seconds .
if i try to start it the other day then i have the same problem

[musicrepairs]

Does anyone have the info on the “off” signal to the hca2400 power amp module. I have installed a new amp module in a pmp5000 and no sound. I can trace a signal all the way to the amp module. Supply rails for the amp module are ok. I can’t get the amp module to turn on. The off input goes to a comparator, but I fail to see why the module won’t turn on.

[The Dude]

I believe there is a triac on the output/jack board of these things (part of a crowbar circuit). Have you verified it is not shorted? It's easy to check. Just measure the resistance across the speaker output and see if there is a short or near short there.

[AaronT]

its usually C66 (startup mute delay capacitor)