[Hallicrafters] HT-33A Fan Assembly Needed

[Roger (K8RI)]

Point taken.

Carl wrote:
>
>   
>> Al Parker wrote:
>>     
>>> Hi Gary,
>>> Yup, you've got it.  I think some of the guys haven't realized that
>>> this tube is an external anode, finned, air cooled, tube similar in
>>> configuration, but bigger, to  a 4CX350 series, etc.  It requires a
>>> specific air flow to properly cool it, and that necessitates more
>>> pressure than what's required to cool glass 3-500's, 4-400's, etc.
>>> I had a "modified" HT-33 for several yrs, but sold it last yr due to
>>> acquiring a Henry 3-KA which replaced it.  You can see at
>>> <http://www.boatanchors.org/HT-33hb.htm>  I thought there might be a pic
>>> of the bottom, showing the fan, but guess not.  I do have a complete,
>>> nearly original, HT-33B that I can drag out & get pix or info if you
>>>
>>>       
>> The stock fan in the HT33A and B does not move a lot of air, nor does
>> the PL172/8295A need a lot with much back pressure.  It'd take one whale
>> of a fan to get much back pressure with that tube.  The tube has a very
>> large anode, almost twice the size of a 8877, and has a very coarse fin
>> structure. It is rated at 1000 watts plate dissipation, can be run from
>> class A to C in the 33A and B series with front panel bias adjust. In
>> class B at the old legal limit the tube was loafing along and in mine
>> only gets warm. IOW at 1000 watts DC input, or 2 KW PEP the tube is
>> running only 400 to 500 watts of dissipation, or half it's design max.
>>     
>>> need.  It's a future project, I do have one good tube for it.  There've
>>> been threads on the Halli & BA reflectors every so often abt those
>>> tubes, and the fact that most glass ones are gassy by now.  It's said
>>> that keeping filament voltage on them every month or 3 is helpful,it
>>> might be, but it won't restore a real flat one (experience).
>>>
>>>       
>> I've found a lot of duds that died from lack of use. I've also found
>> some very old ones that worked just fine. If it hasn't been run in a
>> long time, just plug it in and let the filaments run for a few days
>> before turning on the plate voltage and hoping for the best.
>>
>> So far I've had very good luck with the 33Bs but just remember they are
>> built for 1 KW DC input, not 1500  out.
>> They are also Pentodes and not triodes.
>>
>> 73
>>
>> Roger (K8RI)
>>     
>
> That will work only if the cathode is the getter. If it is the plate it will 
> have to be run. One way is to run low HV and enough positive bias to get 
> sufficient idle current; many gassy tubes (not leaking air) can be restored 
> that way.
>
> Carl
> KM1H
>
>
> ______________________________________________________________
> Hallicrafters mailing list
> Home: http://mailman.qth.net/mailman/listinfo/hallicrafters
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Hallicrafters at mailman.qth.net
>
> List Administrator: Duane Fischer, W8DBF
> ** For Assistance: dfischer at usol.com ** 
>
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
>