Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: JustMike on January 25, 2015, 09:45:58 am
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it fires up, tubes glow but no output on either channel. Where should I begin? The owner said he had the (original) tubes tested and they were good :icon_biggrin: , but even so, if I don't see any red plating or dead filaments, I should hear something, right?
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Need more info. Ask the owner some more questions, like how did it die. Get some voltage readings. Find out what is working and what is not working.
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Get some voltage readings.
+1.
When taking voltage readings, listen to the speaker. Start at the output tube plates for your measurements, and check for d.c. volts.
When probing plates & grids, you might hear a little "pop" in the speaker. As you work your way backward to the input jack, the pops will get louder. make sure volume controls are up a little way when you probe a tube stage before a volume control.
When the "pop" stops, but the volume control is up, you will have found a problem (either see no d.c. volts on a tube; or an open connection like a burned trace, loose connection, or open coupling cap; you might also find a short to ground at a coupling cap or tube grid).