[Hallicrafters] HT-33A Fan Assembly Needed

[rbethman]

Paul,

No, didn't misinterpret.

Note he said "shaded pole fans".  That is the FIRST clue that it is AC, 
AND brushless.

Look at a wall clock motor, a bathroom exhaust fan, and the like.

Computer fans are 12VDC, and do NOT move enough air for ANY amplifier 
that I would own!

Perhaps some 11 meter amps might use such.

Bob - N0DGN

On 4/16/2010 3:53 PM, Paul Kraemer wrote:
> 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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>
>

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