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Mystery componant in a guitar amp

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TacomaRyan

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Hello everyone. I'm bringing an old guitar practice amp back to life and I believe I have found the bad egg after testing everything else with a couple of different multimeters. The only problem is...I have no idea what the heck this little guy is. I do know however that I can't get a continuity reading of any kind out of it. It's a black cylinder with 4 legs (two on each flat side). On one side each leg is marked with either a positive or negative. It is marked "Lt 99". The circuit board printing denotes it as "PH1". I looked into photo transistors but didn't find anything that looked remotely like it. I'm attaching a picture. Any ideas? Thanks!!!

**broken link removed**
 
It's a combination of an LED and an LDR, probably used for the vibrato circuit - it's almost certainly not faulty, and wouldn't stop the unit working in any case.

You can't repair things by randomly attempting to check components with a meter, you need to fault find.
 
You can't repair things by randomly attempting to check components with a meter, you need to fault find.

Amen. So true.

A good place to start would be to make a note of the make of the amp. And then try and find a diagram on the amazing WWW. Once you have a diagram and post it there are plenty audio pro's here that could help you a lot.

Cheers
 
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The PH1 component is a sealed photocoupler. It can only fail if the internal LED is operated outside its operating voltage range.
 
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