[Hallicrafters] HT-33A Repair

[Roger (K8RI)]

Carl wrote:
> How adaptable is the 5CX1500A or B? Those and even sockets appear to be a 
> lot more available.
>   
As the PL172/8295A is obsolete, while the 5CX1500A is still in 
production I'd say they are a lot more available<:-))
I haven't looked at the B version, but the A looks like a nice tube. 75 
Watt screen, 25 watt grid, and the "instant on" Thoriated Tungsten" 
filament (5V at 40A) SK840 socket rather than the SK800B used by the 
4CX-1500B. I don't know how much different the sockets are other than 
the extra ring for the Pentode.  It's about 0.1" longer  and the same 
diameter as the 4CX. It'd be a bit smaller in diameter by almost 3/4" 
than the PL172 and 8295A tubes with much more dense cooling fins which 
means more back pressure required.  I didn't find an air requirement.

It'll put out over 1700 watts (AB1) with 4 Kv on the plate @ 0.700A,  
500 on the screen, G2 grounded
It's a tube I could go for over many others if I had a source as I like 
Pentodes.  I'd only seen them new where they were a tad pricey. I'd like 
to get a pair if I could find a source at a reasonable price. BTW as a 
comparison, the 8295A puts out the same power with 3 Kv @ 0.800A (AB1) 
with 500V on the screen (screen is 30 watts and grid is 0.5W) with 50 
watts drive. Filament is indirectly heated oxide coated 6.0V @ 8.2A

CPI/Eimac has the data sheets on-line.

It looks like one rugged tube, comparatively speaking.
> Carl
> KM1H
>
>
> ----- Original Message ----- 
> From: "Roger (K8RI)" <Hallicraftersgroup at rogerhalstead.com>
> To: "John Hensley" <w5jv at hotmail.com>
> Cc: <hallicrafters at mailman.qth.net>
> Sent: Thursday, December 17, 2009 5:31 AM
> Subject: Re: [Hallicrafters] HT-33A Repair
>
>
>   
>> John Hensley wrote:
>>     
>>> By spring I should be knee deep in this repair and would like toexchange 
>>> emails with anyone who has "been there, done that" regards the HT-33A.  I 
>>> have ordered the Harback filament & biastransformer as well as the 110V 
>>> version of the soft-start add on.
>>> Left to plan out is a replacement capacitor array
>>>       
>> Doesn't that have an oil filled cap?
>>     
>>>  and the rectifiers:either 3B28, K2AW silicon's or two surplus SS 866A 
>>> replacements.
>>> Please reply via private email.  If you've got the same project aheadof 
>>> you maybe we can share notes.
>>>
>>>       
>> I think this is a project many would be interested in.
>> I rebuilt an HT-33B which is not much different. I decided to keep the
>> mercury vapor rectifiers for originality, but replaced the tube with an
>> 8295A version instead of the PL-172/8295A, they are different physically
>> and about a half inch taller. A lot more expensive too if you have to
>> purchase one that is guaranteed. I did not have to replace any of the
>> transformers or chokes.
>>
>> 73
>>
>> Roger (K8RI)
>>
>>     
>>> Thanks,
>>> John
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