07-11-2025, 11:21 PM
Quote:The output valve grid coupling capacitor, 0.01mf, is slightly leaking, it will be monitored as soon as power is applied and if the grid voltage gets a bit too positive it will be changed.
No point in not changing that immediately.
Also any paper caps on screen grids as the leakage will kill gain.
Without a 400V leakage tester, one solution is to remove all the valves and apply HT. Then check the voltages. All paper dielectric caps, unless hermetically sealed cans, leak badly after about 10 years. Water dissolves in the oil/wax/paraffin and into the paper. They are often OK at transistor radio voltages, but not at 50V +
