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December 03, 2022, 07:51:31 PM

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Am I reading this correctly and does this look suspicious?

Started by Den., December 28, 2021, 04:26:15 PM

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Den.

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".

Loudthud

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

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.

Quote from: Enzo on December 28, 2021, 07:00:48 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

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