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Help--Need a Harman Kardon 430 tech.


JohnW

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I think that green disc capacitor is an oops we gotta add this. it should be 47 thousand pico farads, hence the marking 473P. Any way can you unsolder the B3+ output wires and determine if the rectifier board itself is blowing the fuse or something further down the line.

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24 minutes ago, babadono said:

I think that green disc capacitor is an oops we gotta add this. it should be 47 thousand pico farads, hence the marking 473P. Any way can you unsolder the B3+ output wires and determine if the rectifier board itself is blowing the fuse or something further down the line.

This appears to be the next step. Though I'm not sure which wires to remove. 

 

 

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I would have your meter on a higher voltage range when reading voltage across the resistor. If it is smoking the way it did in the video there must be a lot of current flowing through it which will cause a voltage across it greater than 2v. Maximum current for the 1/2 watt resistor is 243mA which works out to 2v. If you are on the 2v scale it won't read the voltage because you are most likely well above the 2v which is why it's smoking.

 

Use the 20v range on your meter and test again. It's simple physics, you cannot have a resistor burn up without current passing through it, and you cannot have current passing through it without a voltage across it.

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32 minutes ago, JohnW said:

Though I'm not sure which wires to remove. 

The ones going to the loads not the inputs. So if I am decoding the manual properly/sufficiently I would say the red,orange and possibly the white/orange. Double check me please @captainbeefheart. It is possible that the filter caps are dried out old electrolytics and are not performing as they should. Also there is a member here who fixes Klipsch subwoofer amp boards and he swears that glue sometimes becomes conductive.

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9 minutes ago, babadono said:

It is possible thatthe filter caps are dried out old electrolytics and are not performing as they should.

 

The filter cap (C4) is on the rectifier board and is connected via a trace. It's painfully clear that we still have a major problem so the rectifier board should be removed and fully tested. We just need to find if the fault is on the rectifier board or after it on the load side where LP53 connects.

 

 

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You are absolute certain those are 8.2 ohm resistors and not something like .82 ohms? Can you test the meter and test leads with a battery or something to make sure the meter and test leads are working. Something is clearly way off in reading across the resistor. There is a lot of current passing through it which if it is actually 8.2 ohms then we should be seeing quite a bit of voltage across the resistor.

 

Something to try to see if the issue is the rectifier board or the load side of the regulator is remove LP53 wire and place a current limiting resistor in series, 100 ohms should do and see if that slows down R9 being smoked. If it does then we know the problem is not on the rectifier board.

 

 

 

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6 minutes ago, captainbeefheart said:

You are absolute certain those are 8.2 ohm resistors and not something like .82 ohms? Can you test the meter and test leads with a battery or something to make sure the meter and test leads are working. Something is clearly way off in reading across the resistor. There is a lot of current passing through it which if it is actually 8.2 ohms then we should be seeing quite a bit of voltage across the resistor.

 

Something to try to see if the issue is the rectifier board or the load side of the regulator is remove LP53 wire and place a current limiting resistor in series, 100 ohms should do and see if that slows down R9 being smoked. If it does then we know the problem is not on the rectifier board.

 

 

 

Just tested voltage on a motorcycle battery. 12.45v.

AAE21DA1-3832-4B30-BF72-AED22EDA6625.jpeg

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6 minutes ago, captainbeefheart said:

I zoomed in on your meter and see what the problem is. You have your meter set to DC volts and you want to be reading AC volts since it's before the rectifier. Sorry I didn't make this clear before.

Dude, you are unbelievably patient. Thanks again.

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It started out pretty high current, reading over 3v which would get that resistor smoking soon but then it settled right down to .5 volts which is about what I would expect to see with the unit working correctly. It could be a bad capacitor that is shorting out during power up but then the oxide layer decided to form correctly and that's why current dropped down to normal.

 

That's why I like doing things like reading current through resistors, you can see exactly what is happening. With the 3v reading that resistor was dissipating around 1 watt. But once it settled down to .5v that is most likely what you want to see with the circuit working correctly.

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