[Hallicrafters] HT-32B

[Langston, Mike]

After many suggestions on how to check my concern about the power xfrmr, I have done the following:


*         Replaced both final tubes with a new matched set

*         Replaced both HV ceramic caps (top and bottom of rf choke)

I put the primary on a variac and inserted a Simpson milliameter in the plate circuit with a VTVM measuring plate voltage. The output was run through a wattmeter to a dummy load. Here's what happens:

I ran the variac up to a plate voltage of 500. After about one minute, the voltage dropped back to 375 and the plate circuit began to draw current. I ran the voltage back up to 500 and noted plate current as follows:


*         500 v = 24 ma

*         600 v = 34 ma

*         700 v = 46 ma

*         800 v = 70 ma

All of the above is with no drive. Switching to MOX and gradually applying rf while peaking drive and final tune, I get about 10 watts out at 800 volts with plate current measuring about 200 ma. The plate current at this point starts to rise slowly but accelerates rapidly. How far it might go is unknown because I chicken out and cut the rf drive back before smoking something.

Disconnecting the HV lead at the input to the rf choke and measuring HV at that point (output of filter choke/capacitor - no load) with the variac at max, I get 1090 v. This remains steady so the transformer, choke and filter cap seem to be fine.

I know this has got to be something simple to find if I just knew how to go about doing it.

Any further suggestions on what to try next would be appreciated.

Mike KL7CD