Harbinger Class D Amp with Crossover - No Output

DIYaudio Members:

My friend asked me to look at his Harbinger Powered Speaker. It uses a mono Class D amp with the IRS2092S amp module. Currently, there is no output. I am hoping Harbinger will send me a schematic. The output seems to be going to a Second Order Crossover that is on the Power Amp / Power Supply Board. I am looking at generic schematics for the IRS2092S but there seem to be differences.

The Low Speaker output has 40 volts dc on it. So there is an issue. The two Mosfets tested good. The board also uses a TIP41C NPN transistor - also tested good.

The Power Supply is your traditional Transformer, Bridge Rectifier, two caps. The plus and minus 50 volts are working. I am not a Class D expert but it seems rare that this Class D amp is not using a SMPS.

Any ideas on troubleshooting or trying to find a schematic that might be close to this particular unit?

Thanks in advance, Tom
Check the IRS chip is oscillating, if it is not then one side is latched on, the high side.
Remove any load first and check for oscillation of approximately 450kHZ.


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Well... it appears I can now pass a signal. I will test the amp over the next few days to make sure it continues to work. When I look at Pin 14 (High Out) on the chip, I see a nice square wave , 700mv. But Pin 11 (Low Out) has a weirdo looking square wave and only 93mv. Maybe it is supposed to be that way? I am not familiar with how this IC works. Anyway... I will follow up in a couple days. Thanks again Jon and Nigel.


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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.



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Hi TomCarlos,

I have on my bench a 2115 with the same problem - DC across the "low" speaker output. Thanks for posting the schematic, it's an immense help.

I know it's an old thread, but hopefully you still remember the details.
I was just wondering what ended up being the fix - based on your description it sounds like you just took the MOSFETs and complementary power transistor out, reinserted them, and that was all. Is that accurate? If so, do you think it was simply a solder joint issue? I can't quite see how that could create this problem.

No problem if you can't recall, again thanks for posting the schematic.
Hey AshlandSoundMachines,

Did you ever find out why you had DC across the the speaker out ? I have the same issue, I replaced a few components mosfets, resistors, diodes and the IRS2092. Thought everything was golden because I had a sine wave and nothing was putting out magic smoke anymore. I put with a dummy load 8ohm resistor on and it was heating up fast. Metered and saw I have rail voltage on the outputs -53V.

Anyway i'm at a loss here, maybe someone can point me in the right direction.
Hey, sorry I should have mentioned I put both Mosfets back on before scoping the gate. The top picture is pin 1 Q4 bottom picture is pin 1 Q5. Still negative 22v DC on the Low out.

Looks like both gates have negative DC voltage??
Q4 pin 1 -30VDC
Q5 pin 1 -55VDC
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