Harbinger Vari V2112 Powered Monitor Speaker - No Output

[TomCarlos]

MEF Members -

I am looking at a Harbinger Vari V2112 Powered Monitor Speaker that has no output. There is a turn on thump so we know something is getting through to the speakers, but nothing else.

It appears something is wrong in the Power Amp section but without a schematic, I am lost. Even if I had one, I am unfamiliar with Class D.

The amp is generating plus and minus 50 volts for the high power supply. The amp is also generating plus and minus 15 volts that is present on the input pc board. I can see the input signal on the cable going back into the power amp but that is where the trail ends.

I wrote to Harbinger waiting to see if there is a schematic or replacement board. Other than a few parts, everything on the PS / Amp board is micro electronics. So chances are, it may be for replacement only. The sad thing is that one can buy this Monitor Speaker for $150 - so maybe we are wasting time here?

On the board, you can see the two large filter caps. To the left is the bridge rectifier. Behind that is the toroid power transformer.

Any ideas on something I can give a quick check to?

Thanks,

[Jazz P Bass]

How about a pic of the output transistors?
Look to see if they are shorted.

[Helmholtz]

Remove speaker and check for DC at the amp's output. High DCV can easily toast a voice coil. So also check the speaker and only reconnect if/when there is no DC.

[TomCarlos]

Thanks...

I will check the output for dc and will pull the heatsink to check the transistors. Will report back tonight.

Tom

[TomCarlos]

Back....

On the Amp board, there is a 7815 Positive Regulator and 7915 Negative Regulator. I measured plus and minus 15 volts on the preamp board so these are ok.

There are four devices attached to the heatsink.

On the far right, there is a JUC-31F Thermostat. I am not sure how to check that.

Next to that is a single TIP41C NPN Transistor. I pulled that and checked with my Atlas Analyzer - it is ok.

On the right side, there are two IRF 640N Mosfets. Again, I checked that with my Atlas meter and they are ok.


I am measuring 42 volts at the Low Output (on the connector) and 0 Volts on the High Output (on the connector).

Behind the Mosfets, there is an inductor (in a black case), another inductor behind that (would), the big yellow cap and another mica cap (removed) that make up the crossover? I am guessing this is a second order crossover.

So... just wondering... how is it that I have 40 volts on the low output but 0 volts on the high. I am trying to follow the traces to draw up the output, through Xover to the speaker connector.

EDIT and UPDATE - This amp uses the IRS2092S amp chip.

[TomCarlos]

Update - today, the amp is working.

This Class D stuff sure is different. But I got a couple hints over at DIYaudio to help me look for key indicators.

After reinstalling the Mosfets and TIP41C, I put the scope on the Low and High outputs. Low and behold, I had a sine wave of 440Khz at 7vrms. I no longer measure any DC at the low output. I also checked at the chip. Pin 14, the High out had a nice symmetrical square wave (700mv). Pin 11, the Low out had a funky-do looking square wave and only 93mv. Maybe that is the way it's supposed to operate? I'm not sure. So maybe there was a bad solder joint? Who knows... double sided board, thin traces, who knows.

I will keep the board on my bench and test over the next few days before I put the amp back in the case.

I think I'll buy me an LJM L15D Pro Power amplifier mono KIT - same chip - a good learning experience. And look no micro components!!

[The Dude]

Those FET's don't look like they are soldered very well. I'm guessing the reason that you have DC on the low output and not the high output is because the high output has a crossover cap in line that is blocking the DC. Your datasheet link for the IRS2092S has a sample circuit shown. Your amp is likely very similar or at least similar enough for troubleshooting. If you have both +&- supplies to the chip and the FET's are good, but still have DC on the output, it's likely the chip is bad.

Edit: Sorry, I was typing while you posted. I'm betting it was connections to the FET's.

[TomCarlos]

Epilog:

For those interested, here is a copy of the schematic for the Power Supply and Amp. It's interesting to see how they modified the typical IRS2092S application to fit their needs. I can now see how they created to Low and High outputs.

Thanks to our friends at Harbinger for sending this to me.

Tom

[The Dude]

Yep. It's just like a crossover built into any passive 2 way speaker. It's just built on the amp board instead of being on it's own board.

[Vinh]

Hi guys,
Sorry to bring back this old thread, I am trying to fix the amplifier for my V2112 speaker. I need help identifying C25. It says 474/64V, is this means it’s 474 farad capacitor? Thanks for any help

[The Dude]

C25 is .47uF/63V. If it were farads, it would be massive.

[g1]

Here is a handy calculator for you. You can use it for any 3 digit capacitor value.
https://kiloohm.info/3-digit-capacitor/474

[The Dude]

I learned it this way. The last digit of the 474 is how many zeros to add to get picofarads. In other words, it's 47 with 4 zeros after, or 470,000 picofarads. Move the decimal point 6 places to the left to get uF, so it's .47uF.

[Vinh]

Thank you all for the info. It’s a 5cm width .47 micro farad. It blew up on my board so I can’t see what is on it. Hopefully this fixes the problem

[g1]

Do you mean 5mm? 5cm would be pretty big for a 63V cap.