06-30-2015, 03:21 PM
Use common sense.
Once you have established the B+ power and your filament voltages are OK (easily detectable), start mapping voltages across the tubes.
It is normal for anodes of most tubes to be at high enough voltage (100V-250V, or a bit more in case of audio output ones), the screen grids should be also fairly high, almost equal or a bit less than anode voltages, control grid is at low DC potential, and Suppressor grid is at Cathode potential.
Absence of Anode voltage is a good indicator of the load open, like the primary of an interstage RF/IF transformer.
Voltage chart helps but I rarely actually look at voltages against the chart values, I just look at the absent/present and the value if it makes sense. Like, on a plate detector Anode voltage of 250V does not make sense. It should be much lower. On the other hand in the output pushpull stage Anode voltage of 80V does not make sense - should be almost as high as B+.
Once you have established the B+ power and your filament voltages are OK (easily detectable), start mapping voltages across the tubes.
It is normal for anodes of most tubes to be at high enough voltage (100V-250V, or a bit more in case of audio output ones), the screen grids should be also fairly high, almost equal or a bit less than anode voltages, control grid is at low DC potential, and Suppressor grid is at Cathode potential.
Absence of Anode voltage is a good indicator of the load open, like the primary of an interstage RF/IF transformer.
Voltage chart helps but I rarely actually look at voltages against the chart values, I just look at the absent/present and the value if it makes sense. Like, on a plate detector Anode voltage of 250V does not make sense. It should be much lower. On the other hand in the output pushpull stage Anode voltage of 80V does not make sense - should be almost as high as B+.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
