Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: fossilshark on May 02, 2025, 06:12:42 pm
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Hi all! this 5150III has a very strange issue with the pilot LED. It is very dim and flickers.
The strange part is: I already rebuilt the +15v and -15v supply to get the amp working, I measure absolutely no AC on the +15v and -15v lines (I even checked with an oscilloscope, perfectly flat) and the flickering is not corresponding with any output levels or me wiggling the LED connections. I cleaned and re-installed the pilot LED with no change.
Any ideas on what could cause this?
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It's a red LED? My 1st thought would be a ground connection, a possible faulty LED, or a bad connection in the LED circuit.
But different color LED's require different currents. The schematic shows red.
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Yes it is a red LED. I also thought ground connection but it is tied to the same trace as the 15v supply GND so I would expect other issues if that was the case. I am really scratching my head on this issue.
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I already rebuilt the +15v and -15v supply to get the amp working,
Including new voltage regulators?
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try another LED