[Amps] Alternative cooling strategies for SB-220?

[Bill W5WVO]

After reading all the suggestions (serious and otherwise), I am
left with only one really appropriate and practical option: Leave
it the way it is.

(a) The tubes ARE graphite anode 3-500Zs, and (b) I do operate
mostly WSJT digital modes, full carrier 30 seconds on/off, or in
the case of EME, one minute on/off. So maximum cooling is
required. I'm not comfortable with slowing down the fan given
these two realities. I will just have to live with the noise.

Thanks for all the feedback, guys, both on and off the reflector.

Bill W5WVO


----- Original Message ----- 
From: "Bill K2OWR" <k2owr at comcast.net>
To: "Carl" <km1h at jeremy.mv.com>
Cc: <amps at contesting.com>
Sent: Thursday, December 17, 2009 1:09 PM
Subject: Re: [Amps] Alternative cooling strategies for SB-220?


> :::: I'm very thankful someone finally called this discussion,
particularly
> relating to possibly water cooling an SB220 amplifier,
"impractical"....
> I can think of other words, but I'm new here, so I wouldn't want
to be
> obscene.
> BILL
>
>
>
> ----- Original Message ----- 
> From: "Carl" <km1h at jeremy.mv.com>
> To: "Rob Atkinson" <ranchorobbo at gmail.com>;
<amps at contesting.com>
> Sent: Thursday, December 17, 2009 15:03
> Subject: Re: [Amps] Alternative cooling strategies for SB-220?
>
>
> > The SB-220 fan draws air in from the rear and the output is
split by the
> > chassis to pass over the socket pins and the glass envelope.
It exhausts
> > thru the top and side perforations.
> >
> > Remoting a fan is impratical due to the friction loss and a
big blower
> > would
> > be needed.
> >
> > Nice to talk about for 3 days but not very practical.
> >
> > As I said before, add a resistor or as another said, go back
to the stock
> > fan. However graphite anode tubes need the extra air if those
are being
> > used.
> >
> > Carl
> > KM1H
> >
> >
> >
> > ----- Original Message ----- 
> > From: "Rob Atkinson" <ranchorobbo at gmail.com>
> > To: <amps at contesting.com>
> > Sent: Thursday, December 17, 2009 2:09 PM
> > Subject: Re: [Amps] Alternative cooling strategies for SB-220?
> >
> >
> >> Not sure what mode you want to operate (i.e. what duty cycle)
but if
> >> high d/c the duct trick with the blower remoted may have this
problem:
> >> the 220 fan is normally placed in the cabinet in such a way
that air
> >> is drawn in through the p.s. from what I remember of it.  If
you run
> >> duct direct to the rear hole next to the RF deck, you loose
that p.s.
> >> cooling through the v.doubler and B+ transformer.  But I have
no idea
> >> how hot the p.s. gets under normal condx or if it gets hot at
all.
> >>
> >> Another thing you can try is a tx keyed relay switch on the
power line
> >> to the fan that bypasses a resistor on tx but is n.o. so the
fan power
> >> goes through a voltage dropping resistor to slow it down so
it is only
> >> full speed and noisy when you are transmitting.   You have to
wire it
> >> so the fan is not powered in series with one side of the B+
primary
> >> (if that is the stock SB220 arrangement).   If you make a
long RTTY or
> >> SSTV tx and the tubes get real hot you will need to use a
timer relay
> >> with a set delay time so the fan speed drops around 30
seconds after
> >> you switch to rx.
> >>
> >> Just some ideas.
> >>
> >> 73
> >>
> >> Rob
> >> K5UJ
> >> _______________________________________________
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> >
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