[Amps] SB220 cooling was: Re: Coupling a blower to an air system socket

[Carl]

Many have reported that the Harbach fan cools less than the original and 
leaves hot spots on the tube. The Heath fan has to be cleaned and lubricated 
to stay at speed, the blades have to be positioned as per the manual, and 
that small aluminum plate on top must be in place to divert the air.

With several hundred SB-220's coming thru here since 1970 Ive yet to see a 
filament pin or socket problem when all the above was correct.....and not 
used by some CB idiot flat out on AM.

Carl
KM1H


----- Original Message ----- 
From: "Pete Smith N4ZR" <n4zr at contesting.com>
To: <amps at contesting.com>
Sent: Monday, March 18, 2013 6:29 AM
Subject: [Amps] SB220 cooling was: Re: Coupling a blower to an air system 
socket


> For what it may be worth, I seem to have cured a recurrent problem with 
> overheated filament pins on my SB-220 (which came unsoldered frequently) 
> by putting a muffin fan directly over the tubes, sucking air out of the 
> tube area.  The amplifier is used in contestservice at ~1200 watts output 
> on the lower bands and around 1KW on 15 and 10.  I had tried all the usual 
> fixes - swapping the socket springs, polishing the pins, adding the 
> Harbach fan - but this appears to have been an essential last step.
>
> 73, Pete N4ZR
> Check out the Reverse Beacon Network at
> http://reversebeacon.net,
> blog at reversebeacon.blogspot.com.
> For spots, please go to your favorite
> ARC V6 or VE7CC DX cluster node.
>
> On 3/17/2013 2:03 AM, Roger (K8RI) wrote:
>> I do not know of any way to achieve the required air flow at a reduced 
>> back pressure other than an exhaust fan reducing the exhaust pressure 
>> thus making it a little easier to get more cooling air through.
>> I believe Emtron and OM both use this approach on some models.
>
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