----- Original Message -----
From: "Patrick Barthelow" <apolloeme@live.com>
To: <sub1@rogerhalstead.com>
Cc: <amps@contesting.com>
Sent: Wednesday, April 06, 2011 4:07 AM
Subject: Re: [Amps] Alpha vs Henry
>
> Gentlemen:
> If you are pushing for enhanced reliability in a Ham manufactured amp, run
> above its ratings,
> say a Heathkit SB 220, and focus on the heat in the transformer being a
> power limiting,
> or a long term reliability factor, and since I would guess the the source
> of the heat, and probably
> the location of the highest temps is deep in the center of the core
> laminations,
> could you significantly lower the transformer temp where it counts with
> external cooling
> fans on the transformer? If the external core of the transformer under
> heavy Amp use, were
> very hot to the touch, sort of "ouch, that's hot!" with Pain threshold in
> 1/4 second of fingertip contact,
> how hot might that be, and say, if it was say, 190 F on the outside of the
> laminations,
> how much hotter is it likely to be on the inside center core?
>
> Best Regards,
> Pat Barthelow, AA6EG
>
Ive used fans on transformers dating back to the 60's when I ran a NCL-2000
hard in contests. In that amp the large bleeder resistors were right next to
the laminations and the heat reduction was considerable.
The Alpha 76PA now used on the 2nd station had been run in a multi op
Caribbean contest station for decades. The owner placed a fan on the
ventilated back panel and that amp had never had a meltdown until the Big
Bang which brought it my way....it wasnt the transformers fault either.
When contesters and heavy DXers started using the SB-220 at the maximum it
was capable of on CW and SSB they found out the transformer was the weak
link. Once they used fans all was fine again until filter caps began gradual
increasing leakage that went undetected and transformers failed again.
Heat is an enemy of most electronics. Whether it is a vintage radio designed
for 115VAC that needs a bucking transformer, a transceiver heat sink that is
undersized and needs an external fan (my TS-940 for example), sweep tube in
a Drake or other rig, and even a newly built AM rig using vintage glass
bottles, cooling will extend life.
Carl
KM1H
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