[Hallicrafters] HT-37 Question

[David C. Hallam]

I bought somewhat of a basket case HT-37 to restore.  In going through the
resistance measurements, I found infinite resistance at the plate of the 3rd
audio amplifier and both plates of the modulator.  Resistance should be 26K
ohms, which is the resistance to ground in the low voltage supply.  At other
points where you measure this resistance, i.e., the plates of other tubes in
the SSB generator, the heterodyne section, and at the plate of the 5V4
rectifier, the resistance measurements are within tolerance.  To me this
indicates that all three of the audio transformers in the SSB generator have
open windings on the plate side.

At some time in the past life of this rig, it had been wet.  The power
supply transformer, chokes, and filter caps have been tested and are OK.  I
took all of the tubes out of the rig, put in solid state rectifiers and
slowly (over a period of several hours) ran up the voltage with a variac
until I had rated voltage on the filter caps.  I did the high and low
voltage sections separately.

Can anyone postulate a scenario where there would be a failure of all three
of the audio transformers?

73

David C. Hallam  KC2JD