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Author Topic: Am I reading this correctly and does this look suspicious?  (Read 334 times)

Den.

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Am I reading this correctly and does this look suspicious?
« on: December 28, 2021, 04:26:15 PM »
Although I have an identical working board I'm going to try to repair this burned circuit board. This resistor (R55) is small and my eyes are getting old. I see brown, grey, yellow, gold 180K 5%, or maybe red, grey, yellow, gold 280K 5%. And, does this cap look suspicious? The cap on the good board looks much "cleaner".
« Last Edit: December 28, 2021, 04:31:01 PM by Den. »

Loudthud

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Re: Am I reading this correctly and does this look suspicious?
« Reply #1 on: December 28, 2021, 06:57:03 PM »
That resistor looks like 1/8W. At 180K it would take 150V to reach 1/8W. If it is 18K ( multiplier looks like orange to me ) it would take 47V. E=Square root (P*R)

Is there that much Voltage in that circuit ? If it were me, I'd unsolder one end of the resistor on the good board and measure it.

Enzo

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Re: Am I reading this correctly and does this look suspicious?
« Reply #2 on: December 28, 2021, 07:00:48 PM »
Perhaps if you told us the make and model of what these parts are in, we could look on the schematic?

You have a good board?  Stick your ohm meter probes on the good one and see what it measures.

Resistors don't burn up on their own, something caused the excess current.   Very often a semiconductor.

CAp, hard to say.  Replacement cost well under a dollar.  WHy take chances?

Den.

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Re: Am I reading this correctly and does this look suspicious?
« Reply #3 on: December 31, 2021, 06:30:54 PM »
You have a good board?  Stick your ohm meter probes on the good one and see what it measures.
I was trying to avoid having to disassemble it again. But I did. That resistor measured 182K. Replaced the resistor and the cap and now the board functions. Thanks.

DrGonz78

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Re: Am I reading this correctly and does this look suspicious?
« Reply #4 on: January 01, 2022, 02:38:50 PM »
I am still curious, like Enzo was, about what make and model amp we are looking at. Perhaps there is a schematic to look at to figure out what could have burnt up that resistor in the first place.
“A person who never made a mistake never tried anything new.” -Albert Einstein