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Old 13th June 2014, 06:27 AM   #1
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Default Harman Kardon AVR 430 shuts down

I wish I could repair this. I switch the unit on and in a few seconds it shuts itself off. The power switch goes blue then back to white, never gets red.

I tried to check the bias but the unit won't stay on long enough. No help from the service manual. Any ideas, anyone?
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Old 19th June 2014, 09:39 AM   #2
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Check the voltage at the power amp output of each amp (not at speaker terminals). U should connect a DMM to this point and then power it ON.

If you find DC offset more than 50mV, then it needs to be fixed.

Gajanan Phadte
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Old 19th June 2014, 05:16 PM   #3
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I will check that. Not so simple, finding those check points on all those channels!
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Old 19th June 2014, 11:05 PM   #4
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I found two places to measure but not sure I know what to expect. The offset is more than 50 mV at first then settles to nearly zero after a second or two. Then shortly thereafter the machine shuts itself off.

I can't see where to find the other outputs to check their offset. This unit is obviously not designed with repair in mind.

Each amplifier has a low Q choke in the output. I found two of these chokes and used them for test points but can't find the rest of them.

I'm about ready to throw in the towel. No matter how well these units might be designed electrically, no matter how carefully they are assembled and tested, no matter what quality components are used, I consider it a piece of junk if a reasonably competent technician can't work on it.

And there is no adequate technical description of the protection circuitry. I'm open to ideas but my frustration level is high.
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Old 20th June 2014, 04:22 AM   #5
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Other method is to check for the protect output on the controller. Then go back and check the inputs that are responsible for this. There may be four to five of these.

Gajanan Phadte
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Old 20th June 2014, 05:54 AM   #6
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Gajanan. I have searched the board layouts and diagrams in the manual and cannot find where the controller is. The diagrams aren't clear regarding interconnections. I think it may be at the front panel but I'm just guessing.

Can you guide me?
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Old 20th June 2014, 09:26 PM   #7
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Okay Gajanan, I believe I have repaired it. Not knowing where to measure, I decided that it might be a major problem and so began to measure all the little test points for the bias. I figured the voltage wouldn't be the offset exactly but would at least be within a volt or so of it.

I measured a few and when I got to one in particular, it measured zero. I wiggled the little connector and suddenly the unit started working properly! Apparently it was a loose or corroded contact and now everything works. I didn't have to plug in the soldering iron or measure anything precisely or make any adjustments.

I appreciate your comments and without them I would have given up. Thanks!
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Old 21st June 2014, 04:49 AM   #8
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An update. I was happy with the repair and was replacing the cover when I realized the unit was getting very warm. There turns out to be a service bulletin, three pages long, that describes a procedure for just this problem. It requires removal of all the bias boards (I think) and replacing the interconnection cable with hard wiring, avoiding connectors. In addition, the same procedure is done for the fan.

This looks like a lot of work. I'm not sure this 10 year old unit is worth it. But at least I know where I stand with this.
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Old 1st July 2014, 03:21 PM   #9
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