06-19-2007, 09:52 PM
Terry,
Here are the results of the measurements you suggested, and maybe a couple more. The negative grid bias of the 41 tubes seems a little less than you suggested.
Grid bias of 41 tubes: -10.2 and -10.4 V DC
HV secondary winding resistance to center tap: 133.8 and 144.3 ohms (Schematic says 150 and 160.)
Primary current: 1.5 mA AC at 120.3 V AC (about 3 mA AC during warm-up)
Rectifier cathode to center tap: 256 V DC (Schematic says 265)
Secondary voltage across rectifier plates: 503 V DC. Each plate to center tap is almost exactly half the total.
Plate to chassis ground voltage of 41 tubes: 180.3 V DC (the schematic says 175 V DC at that point. I assume that is measured to chassis.)
It doesn't look like a existing overcurrent problem now, unless you think the grid bias isn't negative enough. The wax must have come from an old problem. I guess the temperature of the transformer is normal. What do you think?
Here are the results of the measurements you suggested, and maybe a couple more. The negative grid bias of the 41 tubes seems a little less than you suggested.
Grid bias of 41 tubes: -10.2 and -10.4 V DC
HV secondary winding resistance to center tap: 133.8 and 144.3 ohms (Schematic says 150 and 160.)
Primary current: 1.5 mA AC at 120.3 V AC (about 3 mA AC during warm-up)
Rectifier cathode to center tap: 256 V DC (Schematic says 265)
Secondary voltage across rectifier plates: 503 V DC. Each plate to center tap is almost exactly half the total.
Plate to chassis ground voltage of 41 tubes: 180.3 V DC (the schematic says 175 V DC at that point. I assume that is measured to chassis.)
It doesn't look like a existing overcurrent problem now, unless you think the grid bias isn't negative enough. The wax must have come from an old problem. I guess the temperature of the transformer is normal. What do you think?
John Honeycutt
![[-]](https://philcoradio.com/phorum/images/bootbb/collapse.png "[-]")
