-----Original Message-----
From: Rob Atkinson
Sent: Tuesday, February 19, 2013 5:52 PM
To: Jim Thomson
Cc: amps@contesting.com
Subject: Re: [Amps] Peter Dahl Transformers
You're warping this into an argument for cooling for an entire amp
cabinet. That makes it seem like I was against that.
The original context was about a fan on the plate iron only. My point
was that if you have the B+ supply transformer sitting somewhere and
it gets so hot it has to have a fan on it, then it isn't big enough.
this is probably what would happen with a table top RF amp built for
SSB and CW but being run for AM or RTTY.
### 100% agreed. If you want to run rtty/fm/am/digital modes,
or any other high duty cyle mode, get a real xfmr, that rated to do the
job....with minimal temp rise. Get a real xfmr anyway, (read BIG) even
if for cw/ssb modes. The bigger xfmr's will have way better V regulation
esp when used with a high C filter and bigger wire back to main panel.
## The difference in price between the small xfmr and the big one,amortized
over the next 10-20 years amounts to dick. If you size it too small to
begin with,
you will burn it up, and have to replace it with a bigger one anyway, so you
just
wasted a ton of money. A lot cheaper to just do it right the 1st time.
Jim VE7RF
I have no hesitation about
carving open the cabinet and setting some big transformer that will do
the duty out to one side, and using the fan for the RF deck.
73
Rob
K5UJ
On Sat, Feb 16, 2013 at 6:40 AM, Jim Thomson <jim.thom@telus.net> wrote:
## Nothing wrong with running a small, low speed fan in any HV supply.
The temp inside the
cab should be the same as the room temp. It’s worth it to keep the plate
xfmr, hv electrolytics, bleeders,
eq resistors, and any glitch resistor cool.
## I use filters over my 120mm fans... then push air into the cab. Then
any warm air comes out the other side. That puts
positive pressure inside the cab at all times.... which in turn always
ensures a dust free environment inside the cab. I have
a solid top for the hv cabinets. That way dust can’t get in through the
solid top since it has no holes it.
## Those 7 watt, 65 cfm whisper fans are dead quiet. Easy to slow down
if you want.
Jim VE7RF
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