Hi All,

I'm doing some voltage tests on my Astor HM after recapping, and am finding unusual voltages.

* AC input is at 242VAC.

* AC output are 297VAC and 298VAC with centre tap ground. (measured at pins 4 and 6 of the 5Y3GT)

* Filament winding is ok at 6.3VAC.

* Pins 2 and 8 of the 5Y3GT is at 395VDC.

The schematic states it should be 280VDC after an initial surge of 370VDC. ( Schematic visible https://ibb.co/DDhtfZY and https://ibb.co/7gnKWJn )

That same 395VDC is hitting the plate pins on the other tube sockets, which apparently is supposed to have stepped down to 245VDC.

The unit doesn't have a voltage selector switch, but the input windings have a 200-220 and 220-250 tap, of which the 250 tap is used

Unfortunately, I didn't take any readings before recapping, so I don't know if this is a pre-existing condition.

There are two scenarios. One is that it is not drawing enough current & the biggest power hog is the OP tube. Did you check resistors?

6V6 rarely has good grid resistors and the valve prior to it good plate resistor/s. +/- 20% is considered normal for voltage. Also check the 6V6 cathode resistor and the voltage across it. Might be a tired valve?

Otherwise drop the value of the first filter cap to say 16μF. If everything seems normal

Marc

Hi Marcc,

Thanks for the tips.. I haven't checked the resistors yet.

I think you may be right about the load. I removed all the tubes and reinserted them, now I'm getting 245DCV on the plate of the 6V6 as opposed to the 395VDC I was getting before.

As an added bonus, I'm now happily listening to radio without that annoying hum...