If you ran a drill thru the bolt holes you probably created a short from
plate to plate in doing so.
73
Gary K4FMX
> -----Original Message-----
> From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
> Behalf Of David Craig
> Sent: Thursday, February 12, 2009 2:07 AM
> To: Roger; Gary@doctorgary.net
> Cc: Amps@contesting.com
> Subject: Re: [Amps] Transformer heating (problem?)
>
> 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
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|