Re: Harman Kardon AVR 3700 blown standby power supply
I initially found it on eBay listed as JDS6600(IIRC), but I ended up buying it on Amazon to get it a bit faster. It starts around $85 on ebay, a bit more on Amazon. The one from Amazon came with two sets of output leads, so you don't need to buy more unless you want something special. Here is the amazon link, [URL="https://www.amazon.com/gp/product/B07211YWMK/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1"]Amazon arbitrary function generator.[/URL]
It's set at 5V p-p....
jacampb2
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Last Activity: 05-01-2021, 12:11 PM
Joined: 06-30-2017
Location: Beaverton, Mi
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Re: Harman Kardon AVR 3700 blown standby power supply
Ok, here goes. Please excuse my horribly messy test bench. It is on the very fine edge of organized chaos!
I'm going to do my best to explain what I have done, but keep in mind that I'm not 100% sure I am doing things exactly right. This is a bit of a case of the blind leading the blind...
**Edit** the capacitor in series is a 10nf polypropylene that I had around.
[B]This one is the bad Harmon Kardon transformer, trying to show the whole test setup. Signal generator is 1Khz square wave for...Last edited by jacampb2; 08-03-2017, 03:17 PM.Leave a comment:
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Re: Harman Kardon AVR 3700 blown standby power supply
I kept an eye on it as I went because I have inadvertently flipped it before. I can say that I took the readings on CS immediately after the ring test, and then I went on to do the FB and Drain waveforms. I know for certain I didn't switch it back, so if I fumbled it to 1x, I fumbled back to 10x. Not at all outside the realm of possibility, but I don't think I did.
Thanks,
JasonLast edited by jacampb2; 08-02-2017, 07:01 PM.Leave a comment:
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Re: Harman Kardon AVR 3700 blown standby power supply
Yes, it's a 10:1 switchable probe, set on 10x. I'm not sure what you are seeing, that it is peaking at nearly 4v? I don't have enough experience to know what to expect.
I don't know if it makes a difference, but the power supply was not in the receiver when I took those measurements. I believe I also had the 22R that powers the op-amp supply feed still as well. It's a 1.5hr job to get this thing out of the cabinet. Should I be concerned and pull it again?
Thanks,
JasonLeave a comment:
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Re: Harman Kardon AVR 3700 blown standby power supply
Thanks, I'll definitely take some pics tomorrow. It's pretty simple setup, and was based on riveax_60's ring test description much earlier in the thread. I can't take any credit for this at all. When I stared this repair I didn't even know that you could "ring test" an inductor or transformer.
Thanks,
JasonLeave a comment:
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Re: Harman Kardon AVR 3700 blown standby power supply
Great idea! I'll try to take some pics with the bad transformer when I'm out in the shop tomorrow. Thanks!
**edit** I forgot to mention, I just finished up rewiring this think in the home theater cabinet. It is indeed working again. Seems to be 100% functional.
Thanks,
Jason...Last edited by jacampb2; 08-02-2017, 03:07 PM.Leave a comment:
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Re: Harman Kardon AVR 3700 blown standby power supply
I'm pleased to say that I have the receiver back up and running. I bought a proper function generator and it arrived yesterday. I re-ran the same test I did on the old transformer with new function generator and on both the new and old transformer and have attached the waveforms below. It was definitely a bad standby transformer.
I also have the waveforms of the functioning power supply in case it will help someone else.
Thank you all so much for your help. It was a bit of a long road, but I am...Leave a comment:
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Re: Eclipse XA1000 car subwoofer amp full blast buzz
Carefully check over all of your reflowed solder joints. Dollars to donuts you have a slight solder bridge somewhere now, most likely across the outputs or possibly somewhere in the driver circuitry.
As for the original hum, I would do as suggested above, start by checking the big wet caps. I have seen many car audio amplifiers that the caps did not vent, but instead leaked electrolyte out the bottom. The electrolyte is conductive, and in some cases corrosive. Make sure you cleaned the board thoroughly where the...Leave a comment:
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Re: Harman Kardon AVR 3700 blown standby power supply
My meter would not measure the inductance of the primary either. Initially I assumed it was just below the range of my inexpensive tester or that my tester had a problem. I later measured several different transformer primaries with it and it worked fine. I also tested on known inductors and it worked as well. It may well be that that was my first indication that the transformer was bad.
As for testing, I did not complete all the ring testing that rievax_60 recommended earlier in the thread. The only function generator...Leave a comment:
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Re: Harman Kardon AVR 3700 blown standby power supply
The short answer is no, I didn't. The long answer is that when I said this call took a bit more than a half hour, it wasn't because of trouble convincing them, or having to go through some "tech support trouble shooting steps" before they were willing to entertain selling parts. It was simply because the support person had a thick accent and we were having trouble communicating. She was very helpful, and very patient, but it took the majority of that time to get the different part numbers transferred across...Last edited by jacampb2; 07-27-2017, 12:16 PM.Leave a comment:
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Re: Harman Kardon AVR 3700 blown standby power supply
What do you mean? Are you saying I may have damaged it by trying to test it with 12v 60hz AC? That may well be the case, but I think I had things narrowed down to the transformer before I pulled it and tried my not very well thought out test.
Aside from that, the only other thing I can think of is that this blew just after some big thunderstorms went through. You would have thought the MOVs would have caught any reasonable spikes, but I've heard of lots of mysterious issues following storms. ...Leave a comment:
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Re: Harman Kardon AVR 3700 blown standby power supply
Excellent advice, I will definitely do it and post a screen shot, maybe it will help someone else in the future.
Thank you,
JasonLeave a comment:
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Re: Harman Kardon AVR 3700 blown standby power supply
I called Harman Kardon tech support and they were willing to sell me the transformer. It took a bout a half hour to get it all taken care of, but in the end it was only about $15 shipped and my time is worth that much.
I still might tear down the old transformer and try to rewind it when I get some of my other backlogged projects done, but for now I will try out the new factory replacement.
It looks like it will be a week or so before it comes in, I'll post back when I get it installed and let you...Leave a comment:
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Re: Harman Kardon AVR 3700 blown standby power supply
I forgot to add above, I was using a very inexpensive "Function generator" (part of one of those ATmega based tranasistor testers) for the 1khz square wave. I tried to find the output impedance, but the spec is not published. I measured the output impedance by adding parallel resistance between the generator and the scope until I got to half of the unloaded p-p value. I read that this should give me a very close approximation of output impedance. I got 806R for the the measure output impedance.
Thanks,...Leave a comment:
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Re: Harman Kardon AVR 3700 blown standby power supply
Ok, I think the results are in...
First waveform is a known good SMPS transformer. 1kHz square wave fed through a 10nf poly cap (in series) with the scope across the same winding. When I short any other windings on this xformer, the ringing drops to 1-2 cycles and the amplitude drops dramatically.
Second is the Harmon Kardon transformer in the exact same setup. Shorting any other winding on the transformer changes nothing. I get a few more cycles from the ring if I check the bootstrap...Last edited by jacampb2; 07-23-2017, 02:47 PM.Leave a comment:
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Thank you, that is what I thought he meant, I just wanted to make sure. I ended up figuring it out. I thought I posted the results of the test but it looks like my reply is missing. I'll add it again in a moment.
Thanks,
Jason...Leave a comment:
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Re: Harman Kardon AVR 3700 blown standby power supply
Thank you for the tips. I will absolutely try to rewind it if it comes to it. I'm going to try to purchase first, I would like to get this up and running sooner than later and I have so many projects going right now that I have to pick my battles!
Thanks,
JasonLeave a comment:
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Re: Harman Kardon AVR 3700 blown standby power supply
Quick question, does the cap go across the primary, or in series?
Thank you!
Jason...Leave a comment:
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Re: Harman Kardon AVR 3700 blown standby power supply
That has been my experience with the search...
I'm really tempted to just build a new standby supply for it. I think I only need rails of ~28Vdc (for the 24V linear regulated supply) and ~7.5dc for the standby 5Vdc. Then what, something like 12V to supply the ICE switcher that does the +/-12Vdc rails...
That's my absolute worst case plan. Hopefully Harman will sell me a transformer if it comes to it.
Thanks,
JasonLeave a comment:
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Re: Harman Kardon AVR 3700 blown standby power supply
I mentioned earlier in this thread that I had a similar thread going on DIYaudio.
Eva brought up something interesting. She said that it is possible that the current sense resistors are wrong, that if they were 10x's higher resistance then they should be, that the switcher would behave similarly. This has me thinking. The schematic specifies 10R and there are 5 in parallel. I had to replace them because all 5 were scorched and reading 1+ Mohm. I used 10R, I measure the resistance of the group at the CS pin because...Leave a comment:
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