> If there ever were candidates for a tube swap the HT-33A & B's are right
> up there with the MLA-2500 and HT-41. There is nothing wrong with the
> tubes except availability and cost.
>
> The sraight 33 uses a pair of 4CX300A's which are another variant of the
> 4CX250's. One of a kind twist lock socket and about 100W more than the
> 250. They have a reputation of seal leakage over time.
>
> I have a SX-115/HT-32A and might look for a tubless HT-33A/B to experiment
> on. The 8877 would appear to be a "natural" in place of the Penta which
> had a reputation of being extremely clean; I never tested one.
The 8295A is much larger than the 8877 although it only has 1000 watts plate
dissapation compared to the 1500 for the 8877. OTOH the fins are coarse
with lots of space so the tuve is easily cooled with a fan rather than
requiring a squirrel cage blower to produce plenty of back pressure. Those
fins are very soft and easily bent, but they are easily straightened as well
so. In a way being so soft they protect the insides from damage from some
pretty good bumps. The biggest problem with that conversion as I see it
would be adding suficient cooling in an unobtrusive manner. That and the
plate transformers all have 110 VAC primaries only.
73
Roger (K8RI)
>
>
> ----- Original Message -----
> From: "Roger Halstead" <sub1@rogerhalstead.com>
> To: <amps@contesting.com>
> Sent: Friday, September 28, 2007 1:47 AM
> Subject: [Amps] The HT-33B and swamped grid
>
>
>> The comments about the swamped grid got me to thinking about the
>> Hallicrafters HT-33B which uses a Beam Powered Pentode (PL-172/8295A
>> witht
>> he straight 8295A being ceramic and metal.) I've had several HT-33Bs
>> over
>> the years and they appeared to work well, even putting out today's legal
>> limit, but I've never really taken a hard look at the efficency or IM.
>> The
>> 33A and B use the same tube, while the straight 33 uses a Tetrode ( a
>> pair
>> of 4CX-300s I believe)
>>
>> Any comments on this one?
>>
>> Roger (K8RI)
>>
>> _______________________________________________
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>> http://lists.contesting.com/mailman/listinfo/amps
>>
>
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