At 2:12 AM +0000 10/18/03, olympus-digest wrote:
>Date: Sat, 18 Oct 2003 01:33:12 +0100
>From: "Julian Davies" <julian_davies@xxxxxxxxxxxxxx>
>Subject: Re: [OM] Re: [OT]Transformers (was Noisy T32 (wax potting))
>
>- ----- Original Message -----
>From: "Joe Gwinn" <joegwinn@xxxxxxxxxxx>
>To: <olympus@xxxxxxxxxxxxxxx>
>Sent: Friday, October 17, 2003 6:50 PM
>Subject: [OM] Re: [OT]Transformers (was Noisy T32 (wax potting))
>
>
> > But for retrofitting a small power transformer, I wouldn't worry about a
>new hole or two, even if it does raise the loss slightly. I suppose leaving
>space so the bolt can have a insulating sleeve would help, as then any
>connection would have to be via the burrs.
>
>It's the burrs that do it.. To clean the hole you would need to use an
>expanding reamer rather than a drill.
>
>
> > I would be far more worried about accidentally damaging the transformer
>while drilling, unless I could remove the core from the winding. If the
>core is removable, then it ought to be possible to deburr the holes. But
>this is a lot of work.
>
>And you'd never get it back together again! The potting varnish is designed
>to penetrate between the laminations and secure them. If you separate them,
>the will be a comlete mes and won't all go back in. If you clean them up,
>you'll end up with aa dry lamiated transformer which will re - define
>buzzing for you.
Yes, but if the core were already potted the laminations wouldn't be vibrating,
so I have assumed that the laminations are loose, permitting disassembly. I
have encountered many transformers with laminations not glued together over the
years.
> > Anyway, this is why I preferred wax potting. No disassemby needed, and
>wax won't hurt anything.
>
>Agreed as long as it's not so thick as to overheat the centre of the coil.
Yes. Although as discussed in other emails, potting may actually improve heat
dissipation, thus reducing the temperature in the center.
> > Maybe it matters for an audio output amp, which has to handle a wideband
>(20 to 20000 Hz) signal without distortion, but for a one-frequency power
>transformer it likely matters far less, so long as the power loss isn't
>excessive.
>
>Depends on the definition of excessive. Eddy currents equal heat production,
>so things can get tricky. You wouldn't want your wall - wart to melt while
>plugged in, would you? Very few people allow these things sufficient
>ventilation, so they can be quite marginal on temperature. Adding heat is
>not good in these circumstances. If they weren't so ugly people might not
>hide them behind the furniture...:-)
Yes, but the original issue was the transformer in a T32 flash. That said,
reports are that the T32's transformer does get pretty hot after a series of
shots. (I don't have any personal experience here, as I have not been tempted
to disassemble my T32, which works fine and doesn't make too much noise.)
> > Valve amps are making a comeback in hi-fi circles (for the mellow tube
>sound) and never died for guitar amps (for a better grade of distortion), so
>a new career awaits you.
>
>I was privileged to work for probably the greatest valve amp designer
>living. I am now privileged to count him among my friends (even though he
>likes N*k*ns). By comparison my "talents" in this area are pitiful, added to
>which, so much of a subsequent life has needed to be absorbed that I can't
>remember most of the old skills.
>
>Not all valve amps are "mellow", but good ones are "clean", certainly more
>so than the best of transistor. Our were serious butt - kickers. His currnt
>ones still are.
I would bet you know far more than you realize. Do you perchance own a copy of
The Radiotron Designers' Handbook, by any chance? If you do, your secret is
out, your fate sealed.
Joe Gwinn
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