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In Reply to: RE: Schematic? Shelf? posted by Lew on May 12, 2017 at 10:44:06
I've ruled out the shelf, it runs just as hot in other locations. Will try other tubes, here are schematics.Thomas
"In a democracy, uneducated voters get the leaders they deserve."
Edits: 05/12/17Follow Ups:
The design IMO sux. The anode resistor value should be 47K. The voltage is WAY too low. 6SN7 sounds better with a hefty B+, like at LEAST 350 VDC. I know there is a strong belief by many that a shunt regulator is the sheet, but, it wastes energy, creates a lot of heat needlessly, and doesn't sound as good as a pass transistor regulator. The Cathode resistor value might be correct for the rather low B+, but, if B+ were where it belongs the cathode resistors would need to revised.My experiences with those 100 and 150 volt Zeners was a high failure rate, and I suspect that due to inductive kickback. When they fail, they short, and the output voltage will go low AND there will be a lot of heat generated as a result of increased current through those power resistors. . Consider replacing them with a string of lower value zeners and use very high voltage capacitors to absorb the inductive kickback when the power is shut off. The very rapid collapse of the magnetic field causes a very high voltage spike that kills solid state devices. MY solution was to use voltage regulator TUBES instead. They looking F-ing kewl, and they don't get taken out by inductive kickback.
Edits: 05/13/17
ALSO, since you are using SS rectifier, you can go much higher than 47 UF for the PI filter. I'm betting one of the zeners is blown, The power supply should be well over 300 volts if the zener leg was absent.
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