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Old 9th December 2004, 10:26 PM   #1
rkc7 is offline rkc7  United States
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Default Klipsch Promedia BASH amplifier

Not sure if anyone around here is familiar with these. I'm pretty sure they are Class D type amps, but if anyone has even looked at these, I don't know. Well, I have the small subwoofer with the plate amp which contained the 6 amps (5.1 speakers), but only the subwoofer is getting powered, none of the other channels work. So, is anyone familiar with the common malfunction with these items? I know that it is common with many of the older Promedia sets (I had one fail before, but replaced under warranty), so I figure someone may know what to look for. At a quick look over, I found a bad resistor (R7, 100ohm, 1/2watt) which is in the power supply, on one of the little side-boards off of the main, right between the large supply capacitors. I figure that's not good since I really first noticed it looked "browned," but was wondering if there's anything else I should look for and where. Thanks.
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Old 10th December 2004, 07:26 AM   #2
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Old 11th December 2004, 08:03 AM   #3
rkc7 is offline rkc7  United States
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There's a small diode on this "PDC" board which the blown resistor is on that is damaged. I can't see any markings on it, but the board has two pole markings unlike the other diodes marked for the cathode, this has it on both sides (the board printing, not the diode). I was wondering what this could be or what to replace it with? I tried measuring with a diode tester and get nothing either direction. I don't think it's damaged in a way which impairs its function, but the glass or whatever it's made of has a chip in it. I can post a pic if that would help.
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Old 11th December 2004, 02:25 PM   #4
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BASH amps are Class G - the rails track the input signal.

If the subwoofer channel works, then I would start by checking the other channels. It might be a safe initial assumption that the power supply is fine.

I have a PM4.1 that I have been trying to fix. What exactly is the PDC board? This might help me know what you're talking about.

I'm not sure what you're saying about the diode. If it is 2 diodes, back to back, in the same package, that is a triac. It will start conducting in either direction once a certain breakover voltage is reached. That is why it is an open with a DC diode tester.

I heard somewhere that the PM5.1 amp is $37 direct from Klipsch.
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Old 11th December 2004, 04:27 PM   #5
rkc7 is offline rkc7  United States
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The "PDC" board is the small board that comes off of the power supply right near the filter caps. It may be a triac, I'm not familiar with what they look like. I attached a picture of the board with the component in question circled. As for the question of what is bad, That bigger top resistor was bad at first, so there was something obviously wrong in the power supply. I got a response from a tech on the Klipsch site, just saying in response to bascially what I said on here that the common problem I was seeing was due to a resistor. Also, I don't see them selling any replacement amps, I wish I could get it that cheap!
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File Type: jpg pdc.jpg (82.1 KB, 412 views)
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Old 11th December 2004, 05:26 PM   #6
rkc7 is offline rkc7  United States
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Another thing. Two of the resistors from the original board (the one I posted is the same board from another item I had), are marked the same (orange white brown gold), but one reads 385 ohms, the other 2.66kohms. This is out of circuit testing. Does that mean the one (2.66k) is bad? Should I replace it with a another 390ohm resistor or leave it 2.7kohm? The color definately is not red violet red which correspond to that value.
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Old 11th December 2004, 05:30 PM   #7
Steven is offline Steven  Netherlands
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A triac has 3 pins, so it is not a triac. But it could be a diac, these are often used to trigger a triac.
http://www.americanmicrosemi.com/tutorials/diac.htm

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Old 12th December 2004, 01:50 AM   #8
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A diac. Yes. My mistake.

Well, since you tested the R out of circuit, if it reads the wrong value it is bad.

I belive you have to call Klipsch, and perhaps hound them. They would lose a lot of repair money if they advertised the amp prices that low. Plus, I imagine there might be a demand for them if you can get a decent 5.1 BASH amp for $37. It might have been the PM2.1 that was $37, now that I think about it. However, it couldn't hurt to check with them and find out.
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