Gary Smith wrote:
> I'm sure no expert, any chance the Iron's not built for 60Hz?
>
> Gary KA1J
>
>
My question would be: has the transformer ever been fully disassembled?
To me the original problem would have indicated this might be a strong
possibility. I'm assuming this is the standard "E" frame with the
laminations interleaved. If so it's possible the laminations may have
been cleaned leaving them to make irregular contact with each other,
causing some current loops, or aggravated historesis (sp?) loss.
It's been over 40 years since I studied this stuff so I may be wrong.
73
Roger (K8RI)
>> 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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