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Help! 2A3 SET quit after hot restart

Mercury99

Member
2010-04-10 1:09 pm
I have a home-built 2A3 SET amplifier. The circuit is very simple. Two stages capacitor coupled with AC filament heating. The 2A3 are EH gold pin.

The amp runs fine except if I shut it off and turn it back on while still "hot". There is no sound. I measured the 2A3 and the plate voltages are around 400V and grid voltages are around 300V and the heater around 40V. I checked the coupling capacitors. There is no leak. The plate voltages of the previous stage are around 170V.

It sometimes refused to start up until I moved tubes around a few times. Can someone help to provide possible root causes? The 2A3 grid leak resistor values are 499K. Could this be a problem?
 

M Gregg

Disabled Account
2010-06-28 11:04 pm
UK
I have a home-built 2A3 SET amplifier. The circuit is very simple. Two stages capacitor coupled with AC filament heating. The 2A3 are EH gold pin.


It sometimes refused to start up until I moved tubes around a few times. Can someone help to provide possible root causes? The 2A3 grid leak resistor values are 499K. Could this be a problem?

Please post a schematic of your amp so we can get more information and ask for specific measurements.

Regards

M. Gregg