Trouble shooting silicon rectifier diodes in power supply.
- Thread starter HowardK
- Start date
260 and 261
8.1 and 7.7 on the cathodes
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You can use either resistance value, so long as its the voltage measured across it. To ground you need the 125 ohm + transformer resistance. Across the 125 ohm, its just the 125 ohm. It will come out to the same current level either way.
slightly lower in triode makes sense too, there is the DC voltage drop in the transformer to consider, so the screen ends up a bit lower voltage than in pentode mode which drops idle current flow. I'd calculate this for pentode mode since its worst-case.
so long as its not more than 13.2 watts plate+screen dissipation you should be fine. If you really want to get more precise about it you can measure the voltage drop across the 220 ohm screen resistor to work out screen current and subtract that from the cathode current to get a precise value for plate dissipation and screen dissipation. Its 12W plate, 1.2W screen in design center for a 6bq5.
slightly lower in triode makes sense too, there is the DC voltage drop in the transformer to consider, so the screen ends up a bit lower voltage than in pentode mode which drops idle current flow. I'd calculate this for pentode mode since its worst-case.
so long as its not more than 13.2 watts plate+screen dissipation you should be fine. If you really want to get more precise about it you can measure the voltage drop across the 220 ohm screen resistor to work out screen current and subtract that from the cathode current to get a precise value for plate dissipation and screen dissipation. Its 12W plate, 1.2W screen in design center for a 6bq5.
