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Tubes Asylum Questions about tubes and gear that glows. FAQ |
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Tubes Asylum Questions about tubes and gear that glows. FAQ |
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In Reply to: Tube Power Amp Not Working - Help? posted by capone on September 5, 2015 at 19:27:47:
I would start by checking the secondary windings AC voltage.Pull the two 5AR4 rectifier tubes. Power up the amplifier.
First check for 5Vac filament winding voltage between pins 2 & 8 on the 5AR4 tube sockets. (If measuring from the top of the tube socket count counterclockwise from the keyway). You should measure 5Vac. If no voltage,(TURN OFF the amp and unplug from AC power), trace the 5 volt filament winding leads, wires, back to the power transformer. (These leads could be twisted together from the power transformer.) Look for a fuse or resistor that may in series with one of the leads that may be blown. While looking look for a possible poorly soldered cold soldered connection that may have burned free making the connection open.
If nothing is in series between the tube socket pins and the transformer then the 5 volt winding is open, burned out.*But if you measure 5Vac......
Next check for AC voltage on the high voltage secondary winding. Be careful the voltage will be several 100s of volts! Measure the voltage from pin 4 to pin 6. If you measure a high voltage of several hundred volts next measure from pin 4 to the metal chassis of the amp. You should measure 1/2 of the voltage you measured from pin 4 to pin 6. Next measure the voltage from pin 6 to the metal chassis of the amp. The voltage should measure the same as it did from pin 4 to the chassis. (I am assuming the high voltage secondary winding is center tapped.)
Post back what you find.
Edits: 09/09/15
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- RE: Tube Power Amp Not Working - Help? - jea48 17:48:25 09/09/15 (0)
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