[Hallicrafters] HT-33A Fan Assembly Needed

[Paul Kraemer]

Ummm, you may have mis-interpreted the root of the message.
There are many type of "Muffin" fans. Those with ac motors will work fine in 
an rf environment. Many fans of the dc brushless type salvaged from or 
designed to be used in modern computers will not work in an rf environment 
at all frequencies. Some have been known to run slow or even burn up in an 
rf field of the right frequency.
So, it isn't the muffin fan,  it is the fact that many of them are not AC 
operated. AC operated ones typically are harder to find, cost more and in my 
experience noisier than the dc counterpart.
Apology accepted
Paul K0UYA

----- Original Message ----- 
From: "rbethman" <rbethman at comcast.net>
Cc: <Hallicrafters at mailman.qth.net>
Sent: Friday, April 16, 2010 2:17 PM
Subject: Re: [Hallicrafters] HT-33A Fan Assembly Needed


> Regarding being "that close to RF".  Hooey!  Amp Supply made their amps
> using one of the high speed 4" muffins blowing across the 3-500Zs from
> the side, no enclosure to protect it, no chimneys on the tubes either!
>
> They also used a resistor to switch in or out for "Lo / Hi" speed
> cooling.  The full legal limit output NEVER bothered the fan!
>
> The SAME fan was used in an old Z-80 based Northstar Horizon Computer of
> OLD!
>
> These are 120V fans.  AT&T used the same fans in some of their
> communications racks/equipment.  I've got a fan system from them that
> was headed for trash as upgrades were done.  That has been over ten
> years ago.
>
> I put the whole frame in the window sometimes if we need to vent fumes
> from over zealous use of a cleaner.
>
> They cool the finals VERY well! (In a commercially built amp.  I even
> run 25W AM in with about a 300W resting carrier out of the amp!)
>
> Bob - N0DGN
>
> On 4/16/2010 2:51 PM, Paul Kraemer wrote:
>> Gary
>> Kudos on the very nice find!
>> WW Grainger has a nice selection of these shaded pole fan motors and high
>> efficiency blades commonly used in small exhaust fans and range hoods. 
>> The
>> old mounting centers were typically 2" which is now 1 7/8", other than 
>> that
>> they are very close fit. I found one for an SB-200 linear. Motor plus 
>> blade
>> were about $17. At the time I noticed that the same one also fit a 
>> Heathkit
>> Warrior and CE 100V
>> The 3.5" computer fans run off a couple diodes on the filament 
>> transformer
>> do a nice job too but many of them don't like being that close to rf.
>> Paul K0UYA
>>
>>
>> ----- Original Message -----
>> From: "garyislander"<gary at garyislander.com>
>> To:<Hallicrafters at mailman.qth.net>
>> Sent: Friday, April 16, 2010 10:37 AM
>> Subject: Re: [Hallicrafters] HT-33A Fan Assembly Needed
>>
>>
>>
>>> It is a bladed fan according to pictures I have seen of a HT-33A..
>>>
>>> I also found a SX-101A and a HT-32A in this same land fill.  Both units
>>> were in rough shape, but after much work I got both to operate properly.
>>> Both units were mice hotels, but they cleaned up pretty well.  Had to 
>>> hand
>>> make several adjustable coils in the HT32A, but thats the fun of 
>>> restoring
>>> these boatanchors.  Some rewiring, replaced some tubes and re-aligned as
>>> close to spec. as possible.
>>>
>>> Have made about 300 contacts with this setup with very good reports 
>>> using
>>> a D-104.  Forgot what it is like to work a contest with a seperate
>>> receiver and transmitter.   Maybe the amp can be saved and put into
>>> operation.....this one could be a long shot!
>>>
>>> Gary K1MQ
>
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