[Hallicrafters] HT-33A Repair

[Carl]

They were used all over the world starting around the late 60's in TMC 
equipment and then in other brands and even FM. Seems to be overlooked 
possibly due to the socket. A friend offered me a NIB pair a few years ago 
for a NIB 4CX1000A but I couldnt oblige.

Carl
KM1H




----- Original Message ----- 
From: "Roger (K8RI)" <Hallicraftersgroup at rogerhalstead.com>
To: "Carl" <km1h at jeremy.mv.com>
Cc: "John Hensley" <w5jv at hotmail.com>; <hallicrafters at mailman.qth.net>
Sent: Thursday, December 17, 2009 3:10 PM
Subject: Re: [Hallicrafters] HT-33A Repair


>
>
> 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 As the PL172/8295A is obsolete, while the 5CX1500A is still in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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