Subwoofer Board Level/Power Supply Repair, did I find the problem? - AVS Forum
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post #1 of 17 Old 05-20-2010, 10:51 AM - Thread Starter
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My infinity PS-10 sub started going goofy a couple years ago. It would start to make popping and/or hissing sort of noises about 2 years ago, even when the volume was muted on the receiver. The capacitors all look okay. I wouldn't say any of them are even swollen, and the fuse is still intact.

The only thing I see out of the ordinary is on the power supply. Please see the attached pics. There are 2 layers that are supposed to be identical I am sure. The top section is a darker yellow/orange and is night and tight and smooth, and is about 1/4 inch inside the outer edge of the power supply. The bottom section is a lighter yellow/orange, and bows out quite a bit from the power supply and I can actually see inside the yellow/orange tape or whatever that is.

1) Would this most likely be the cause of my problem?

2) Can I get another power supply like this? How can I find a similar power supply? This one has 042-010053-003 YT-10616-4 ELY 0441 printed on the top of it.

Any tips, info, suggestions would be great! I would love to get this sub back up and running on my own. I am now going to pull out the woofer itself and inspect for issues there and will update with what I find.
LL
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post #2 of 17 Old 05-20-2010, 11:40 AM - Thread Starter
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Crap. I searched Bing and found this web site as the ONLY result! $86 and it doesn't fully match all the numbers, so it appears to not be an exact match. dang it.

http://www.encompassparts.com/products/?042-010053-003

Again, any tips/info/advice/etc would be greatly appreciated, thanks!

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post #3 of 17 Old 05-20-2010, 11:54 AM
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While it is possible the transformer is bad, I suspect it is something else. IF it overheated and that caused the cover to bow out, it could be a failure indication. However, transformers usually die when a coil opens up, resulting in no sound. It's possible the coil is intermittant, which could cause some loud popping as the supply sycles on and off, but I think it likely the problem is elsewhere. It could be a bad solder connection someplace on the board (or at the transformer).

If you have a decent voltmeter, preferably analog (meter) or digital with a bar graph, you can measure the output voltage and see if it fluctuates on the transformer's output. That might indicate a bad wire in or leading up to the transformer.

Good luck! - Don

"After silence, that which best expresses the inexpressible, is music" - Aldous Huxley
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post #4 of 17 Old 05-20-2010, 12:31 PM - Thread Starter
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Don - thanks for the response. I do have access to a pretty decent voltmeter. Unfortunately I don't know how to use it!! I have attached pics of the voltmeter and the transformer cabling.

There are 2 blue and 2 red wires going out from the transformer, no other wires attach to it.

What voltmeter settings do I need, and then what do I touch with the red/black terminals on the voltmeter? Which wires?

Thanks again.
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post #5 of 17 Old 05-20-2010, 12:44 PM
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Sorry to be negative, but if you don't know how to use a voltmeter you probably won't be able to fix this yourself. Visually inspect the board looking for bad solder joints - you might get lucky and find a bad joint somewhere. More advanced troubleshooting isn't really a DIY project without some basic electronic knowledge.

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post #6 of 17 Old 05-20-2010, 12:48 PM - Thread Starter
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Well, I do have basic electronic knowledge, I simply haven't used a voltmeter hardly at all. I have a soldering iron and have modified 3 xbox 360 controllers using several delicate soldering jobs.

As stated in the OP, I examined the amp thoroughly and didn't see anything as little as an expanded or swollen cap, let alone a blown cap or disjointed solder. Anything like that would pop out as I do board level replacements on PC's for my job.

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post #7 of 17 Old 05-20-2010, 01:55 PM - Thread Starter
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Okay, I figured out the basics of the voltmeter. I got it where I could test 120 volts coming out of the wall outlet. I then discovered there is only a white and black cable coming out from the power switch heading over to the board on the amp.

I tested the ends of those 2 cables both attached and unhooked from the board and they test at 120 volts just like the wall outlet did.

From there, I don't know what to test, as it appears the 2 blue and 2 red wires are inputs to the transformer. As well as a gold colored wire that appears to input to the transformer between the 2 red wires.

I tried testing all kinds of combos of wires, 1 red and 1 blue, both blues, both reds, etc and never got more than around 3 volts or so, certainly nothing that power the sub. The sub does still work though, when I fire it up cold it generally works for a couple hours. At that point the strange noises start to kick in.

I emailed Harman and they claim to have that transformer in stock, even though they gave me a slightly different part # than what is stamped on this one here.

Check out the attached photos and if you can suggest which combo of colored wires to test for output voltage from the transformer. Thanks!
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post #8 of 17 Old 05-20-2010, 07:36 PM
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Hmmm... Honestly, my first response is the same as petew's -- you are dealing with high voltages and currents and could easily hurt or kill (yes, kill) yourself or the amp. I would never hire a tech who couldn't use, or was unfamiliar with, a voltmeter!

If you are determined, start by turning the amp off and unplugging it from the wall. Leave it for 10 - 60 minutes, then measure the d.c. voltage across the caps. Make sure it is zero, or durn close.

Now, trace the wires from the a.c. line input to the transformer. One side probably goes pretty straight to it; the other likely goes through a fuse and switch before the wire goes back to the board and then to the transformer. that's the primary side, and will lead to two wires into one coil of the transformer.

The output, or secondary, side may have several groups of wires. These generate different voltages, for example a low-voltage circuit for any logic circuits and the front end, maybe a medium-voltage one for the driver stages, and a high-voltage coil for the final power amp. Chances are you'll be able to tell by the way the wires are grouped on the PCB (printed circuit board). Check the voltage and make sure it is zero across all the wires (measure from each wire to ground and then across the pairs). Then use your ohmmeter and verify that the resistance between the pairs of wires is low for each circuit. (Using an ohmmeter on a charged circuit can fry the meter.) Gently prod the wires and make sure continuity is maintained (no loose/broken transformer wires). this won't check the wires deep in the transformer, but may indicate a bad solder joint or wire broken right as it comes off the transformer and/or into the board (common stress points).

While you have it apart, take a bright white light and shine on the back of the board. Look carefully as you gently push on various components/wires and see if there are any hairline cracks in the solder joints. A bad joint can be hard to detect, and if it's intermittent may be almost impossible to see until the circuit warms up (maybe not even then).

You can try to check the rectifiers (diodes) with your ohmmeter -- should read high one way, low the other. Other circuit elements may make it impossible to tell without removing them, however.

If you are comfortable playing around with live high-voltage circuits you can power up the amp, clip the a.c. voltmeter to the various transformer outputs, and see if anything happens when the problem occurs. You can also check the d.c. output voltage across the various filter capacitors, again watching to see if the meter fluctuates when your noise happens.

Honestly, you are playing with fire, and blind probing is very hit and miss for something like this. If you aren't terribly familiar with using a voltmeter, I would do the power-off tests, then if nothing obvious shows up, take it to a tech with the equipment and experience to troubleshoot it. You will money, frustration, and possibly a lifetime ahead. The voltages in a power amp are way above any computer/game rig (past the incoming line).

FWIWFM - Don

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post #9 of 17 Old 05-20-2010, 07:55 PM - Thread Starter
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Thanks Don. I actually have used a different voltmeter quite a bit in the past, never this one. I also used to work with 210 circuits that could easily cause an instant heart attack, so I am aware of and very cautious with the dangers or electricity. I already live tested the amp with it plugged in and powered on to verify that 120 volts were coming in from the wall.

Those 2 wires, 1 black and 1 white, plug into the PCB. I believe they are labeled AC1 and AC3 at the connection. Now going out from the PCB to the transformer, is where I don't know what to test. It's hard to tell what feeds into and what goes out from the transformer. I am pretty sure I tested all possibilities earlier, but maybe I missed something.

I did just get an idea though that I will try tomorrow as it's getting late. There are 2 connectors from the PCB to the internal wiring of the sub that feeds the woofer itself. I will power it back on tomorrow and see what volt readings I get from those two connections. Hopefully I can come up with the magic combination that gives me an accurate reading on volts going into and leaving the transformer that I believe is fried. If that is the problem, Harman has it for less than $40 plus shipping. It would be great to get my sub back in working order so cheaply.

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post #10 of 17 Old 05-20-2010, 08:11 PM
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Use the ohmmeter to find which wires go from a.c. line to transformer inputs with the power off. Do as much as you can on the "off" circuit -- easier and safer no matter your experience with live circuits. I power on only if I have to when troubleshooting something like this.

Unless the woofer is transformer coupled in some very strange fashion, there will be no direct connection from the power transformer to the subwoofer (speaker) itself so that won't tell you anything. The ground connection may be common, of course... I must have misunderstood your statement.

Ask Harman if they'll send you a schematic. - Don

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post #11 of 17 Old 05-21-2010, 08:40 AM - Thread Starter
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Quote:
Originally Posted by DonH50 View Post

While it is possible the transformer is bad, I suspect it is something else. IF it overheated and that caused the cover to bow out, it could be a failure indication.... I think it likely the problem is elsewhere. It could be a bad solder connection someplace on the board (or at the transformer).

This. You were dead on. I don't know how I missed it, but I inspected the board further today and did in fact discover a burned out connection. I never even checked the back side of the board until today! I was checking the caps on the top side. None of them had the tops swollen or busting open (which is what I usually see on PC's) so I assumed the caps were all good. Not true!

See attached photo. Harman says they have a replacement amp board for $159 + shipping. That really sucks. If I had a guarantee that my sub would work for several years with no problems, I would do it. Because this really is a good, solid sub with great bass. But, I am worried that $170 won't be a long-term fix.
LL

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post #12 of 17 Old 05-21-2010, 10:38 AM
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I can't tell where the original traces go from the picture. If it were mine, I'd try to remove the offending component, clean up the board (a white plastic eraser can help, and perhaps some contact cleaner), replace the component, add jumper(s) as needed to bypass the burnt traces, and see if it works. If the joint was cold/loose and arcing it may have caused that damage and there may not be anything wrong with the rest of the amp.

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post #13 of 17 Old 05-21-2010, 04:13 PM - Thread Starter
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although I do have a soldering iron, i don't know how to find out exactly which components I need to replace the burned up stuff. Harman won't budge on their amp price. I'm just gonna put the Infinity back in the garage I guess and keep using my Acoustic Audio 12" to get me by. It does ok bass at times.

Don, thanks again for your help buddy.

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post #14 of 17 Old 05-21-2010, 07:13 PM
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Find a friend with an iron and some tech experience. Looks like a six-pack job to me, not worth a case.

"After silence, that which best expresses the inexpressible, is music" - Aldous Huxley
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post #15 of 17 Old 05-21-2010, 07:41 PM - Thread Starter
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Will do thanks. I know a bench tech that would know right away what is messed up and what he can do to sort it out.

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post #16 of 17 Old 10-23-2012, 01:12 AM
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Voltage output of the Power Transformer


hi Muckrak3r,


On your post #8 , the two (2) red wires and yelow are the secondary

terminals of the power transformer.smile.gif




As DonH50 have posted (post #3):



To determine the AC output:,



negative (black) of the multimeter

set at AC volts, >> to yellow wire.


the red probe of the multimeter to either of the two red wire
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post #17 of 17 Old 02-07-2014, 10:34 AM
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Quote:
Originally Posted by Muckrak3r View Post


This. You were dead on. I don't know how I missed it, but I inspected the board further today and did in fact discover a burned out connection. I never even checked the back side of the board until today! I was checking the caps on the top side. None of them had the tops swollen or busting open (which is what I usually see on PC's) so I assumed the caps were all good. Not true!


See attached photo. Harman says they have a replacement amp board for $159 + shipping. That really sucks. If I had a guarantee that my sub would work for several years with no problems, I would do it. Because this really is a good, solid sub with great bass. But, I am worried that $170 won't be a long-term fix.
LL

I'm sure you have moved on, but that burned section was a SMD Capacitor (C71) that burned out.
I just wated to add to that to this thread in case someone else comes across with the same issue/burn spot, to help them point them in the right direction.

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