It may well have been Roger- I can't tell for sure. One thing that
bothered me a LOT was that when redoing the E I core lamination thru bolts,
some of the plates were not aligned properly- I had to grind/drill parts of
the holes to get a teflon-insulated bolt thru it (and it was markedly
smaller than the actual core hole diameter). This is beginning to appear
more & more like a bad transformer design/assembly issue. 73 Dave
----- Original Message -----
From: "Roger" <sub1@rogerhalstead.com>
To: <Gary@doctorgary.net>
Cc: <Amps@contesting.com>
Sent: Thursday, February 12, 2009 1:38 AM
Subject: Re: [Amps] Transformer heating (problem?)
>
>
> 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
>>>
>>
>> _______________________________________________
>> Amps mailing list
>> Amps@contesting.com
>> http://lists.contesting.com/mailman/listinfo/amps
>>
>>
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|