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Class D Switching Power Amplifiers and Power D/A conversion

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Old 23rd October 2012, 06:27 AM   #1
KVP is offline KVP  Belgium
diyAudio Member
Join Date: Aug 2010
Default Is there any hope?

Dear DIYers,

Iím following this forum for quite some time and I must say itís just unbelievable the amount of information one can find. Didnít believe though I would ever post a message myself. I listen quite a lot to music and did already make some amplifiers, or better I bought kits (e.g. Velleman), put them together and they just work. So far so good. Unfortunately I only have a limited knowledge of electronics (Iím an IT guy) so when I encounter problems, itís difficult for me to begin troubleshooting. So here is my problem: I bought some time ago via Ebay 2 amplifiers item 190733464398 from Zoe_Tsang (YJ New 700W 4ohm Mono IRAUD350 IRS2092 IRFB23N15D+speaker protection board). This should be pretty straightforward: connect power AC 45-0-45, input signal, output to speakers and play. Unfortunately not in my case: the little blue LED indicator does light up, speaker protection LED does not turn on but speaker protection relay does not close either. So where to start with my limited knowledge and no schematic? Didnít expect to get it, asked Zoe_Tsang for the schematic anyway, didnít receive it, nor did I get any measuring point to check whatsoever. He suggested sending back the modules but this would cost me as much as buying new ones. Besides, maybe error is on my side since both modules show same behaviorÖ Power is getting to the board (I read approx. +- 65V at the caps), I already shorted the speaker protection because it doesnít close, but also that doesnít give the hoped for result. I must say Iím not using a SMPS power supply, only a toroidal transformer 2X45V AC. Maybe is this the issue? I read in another forum bridge rectifiers are not done for D class amplifiers, which surprises me because they are on the board itself. So what could I check, having no scope and only own a few multimeters? Any suggestion?

Many thanks, regards Ė Koen.
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Old 23rd October 2012, 07:49 PM   #2
Join Date: Jan 2005
Sounds to me like you got sent defective products.

Do you have an oscilloscope ? If no, further troubleshooting will be very difficult if not impossible.

Do NOT bypass the speaker dc protection, its there for a reason! If it remains off, it may well be off for a reason, such as excess DC offset on the output.

The first thing i would check is whats happening before the output filter inductor, using an oscilloscope to determine if the amp is switching or not.

If its not, it might be a faulty voltage regulator for the IRS2092 gate driver, or the IRS2092 is simply a counterfeit part, the same can go with the output devices. This is chechable with a DMM, check if the IRS2092 is getting power by measuring from negative rail to the VCC pin, if no voltage, theres your culprit, either dead reg or dead irs2092.

Btw did he actually include the TDA8920BTH board as stated in the auction or is that just bait to attract buyers ? I will be powering up a Sure Electronics 2x250W class d in around a week which uses the same IRS2092 gate driver.

Last edited by Tekko; 23rd October 2012 at 07:57 PM.
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Old 24th October 2012, 12:15 AM   #3
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Join Date: Apr 2008
Location: Carlisle, England
I have found that there is little to go wrong on the irs2092 amplifier boards.
I usually find the mosfets have blown and sometimes take the 2092 with them, so I always replace mosfets and 2092 regardless.
If the mosfets are ok then you need to check voltages around the 2092 like VCC, VSS, VAA etc I found the 2092 to be touchy about scope probes and I have blown a couple putting cope probes on when powered up.
Anotehr thing to catch you out is making sure the power supply is fully discharged before replacing the 2092. Putting one in with volts still on the supply (caps still charged partly) will blow it up.
Murton-Pike Systems PCBCAD51 pcb design software.
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Old 24th October 2012, 12:35 PM   #4
diyAudio Member
Join Date: Oct 2012
HI,as you are a IT engineer,it is easy to be know theory of electronic,Irs2092 is a single channel gate driver,very easy to be used,
if you have time.refer to my thread:

spend time to study step by step,i make sure you will be not just only a Diyer~~~
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Old 28th October 2012, 09:10 AM   #5
KVP is offline KVP  Belgium
diyAudio Member
Join Date: Aug 2010
Hello again,

Sorry to coming back only now, but I can only work on this during the weekend. First of all thank you for your reactions. Please don't worry about bypassing the speaker protection, I did put another one on the output. Then I did some measuring, for which the result seems quite strange (to me anyway when looking at the IRS2092 datasheet) : VAA = 5,5V, VSS = 5,5V, VCC = 49V. I can also confirm there is no TDA8920BTH on the board. Maybe a typo cause this is not mentioned anymore on his site.

Best regards,
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Old 28th October 2012, 09:42 AM   #6
Join Date: Jan 2005
If the IRS2092 is receiving 50V on its low side drive pin VCC, the regulator for it is definately dead, and thus the IRS2092 is dead too, im actually chocked the IRS2092 dident explode violently, receiving that kinda voltage.
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Old 29th October 2012, 02:13 PM   #7
KVP is offline KVP  Belgium
diyAudio Member
Join Date: Aug 2010
Well, I'm afraid then my journey stops here, because I had the amps already some time in possession so difficult to return back. Moreover sending them back would cost almost the price of a new module. Without any schematic it isn't easy either to figure out where this 49V comes from. Besides, I don't have the gear to work on such tiny parts as the 2092 on the board.

Again thanks for your reactions, maybe we meet again another time,
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