:::: 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@jeremy.mv.com>
To: "Rob Atkinson" <ranchorobbo@gmail.com>; <amps@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@gmail.com>
> To: <amps@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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