I'm sure no expert, any chance the Iron's not built for 60Hz?
Gary KA1J
> Corollary to a previous issue with a B+ transformer I passed thru the
> group a while back, which before I repaired it had a current loop due to
> bad/no insulation on the core bolts. Transformer has a 240V primary,
> 2800-3000V secondary rated at 2 amp CCS. Is installed & in use on a HB GS35b
> 6m amp. When "module" testing the amp the transformer taps met specs,
> measured with a Simpson 260. Calculations based on measurements then
> indicated a 12.5 to 1 ratio.
> Fast-forward to completed amp...After some occassional use (~30 minutes
> of total operating time) am having the following "issues." The 3000VAC
> secondary tap is now only putting out 2700VAC with line voltage measured at
> 243VAC (240V mains line is 10 guage wire, a 10 ft run from the breaker box &
> then 6 feet of 12 guage line to the amp... original measurement taken with
> same lines). The even more disconcerting problem is that after a couple
> hours of sitting at "idle" (amp on, power to B+ but no RF) the transformer
> iron is getting hot- enough that you wouldn't want to keep your hand on it
> for long, and particularly so near the left & right sides of the core. (Yes,
> I checked the plate meter & no current thru tube, bias relay fine).
> Lamination bolts remain cold so no more current loop around the mounting
> brackets.... I am baffled as to why this thing is getting hot just idling.
> There is no "bleeder" per se on the PS, just 6 x 220k ohm Rs across each of
> twelve 450V caps in series. The only other constant current draw is a 5 MEG
> dropping R to the B+ meter. I am baffled as to why the transformer
> laminations would get hot with almost no current draw, and am concerned that
> once I really work this thing out during a contest or Es opening the heat is
> going to short the secondaries.
> Any ideas as to what could be going on? Is this normal, or as I am
> beginning to think, an 86 lb misdesigned piece of junk??? Any input
> appreciated.
>
> 73 Dave N3DB
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