[AMRadio] Modulator troubles


Joe Walden w5jdy at intergate.com
Mon Feb 19 22:54:06 EST 2007


>From Joe w5jdy in Okla.   My experience with a modulator.    I replaced the
audio drive transformer in a Viking II (the one feeding the grids of the
final modulator tubes) with a brand new in the box Hammond Transformer from
Antique Radio in Tempe Arizona...  I had mod current but distorted audio and
a real low modulation per-centage. Even the dummy load light bulb dimmed on
mod peaks.
After many,many moons,the trouble
was located.   The NIB Driver transformer was wired wrong inside.  It had
two individual windings for the grids
 and they were phased wrong inside the transformer.  It was a nightmare...
All
voltages and currents were as the manual stated and I had good audio from
each grid to ground but hardly any audio from grid to grid.   As I say the
mod tubes
were bucking each other... It was running Push-Push instead of Push-Pull?
 I emailed Hammond and they sent me another NIB
same part number transformer NO Chg.and the trouble was totally corrected...
90% Plus Modulation NO distortion.... If you replaced any new parts,look
there first???   w5jdy  Joe in Okla.....







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