[Milsurplus] VT-25/10 subs?

[Richard]

Another option:  A triode connected 6L6 has an amplification factor of 
8, the same as the VT-62/801A and VT-25/10Y.  Further, the triode 
connected 6L6 is good for 500 volts, the same as the 801A.  I made a 4 
pin to octal adapter with a 4 pin tube base and an octal socket glued on 
top, the heater dropping resistor outside, and a wire from the cathode 
for grounding.  Tried it in my TBW (for the 801A) and there is no 
difference.

Richard, AA1P


On 02/23/2018 11:20 PM, Bruce Gentry wrote:
> There are several possibilities. First of all, the 10 has a 7.5 volt 
> filament at 1.25 amps. That is the biggest issue. The filament is fed 
> by two resistors from the 24 volt source. Not only does this reduce 
> the filament voltage, it raises it above ground to help bias the 
> tube.   A triode connected 6V6, 6L6, or 6CA7   should work fine as 
> long as a ballast resistor is added across the heater to bring the 
> voltage down to 6 volts. A 6CA7 with it's 1.5 amp draw might be just 
> about right  with the original filament dropping resistors and no 
> ballast resistor. In any of these cases, the cathode has to be dealt 
> with. It may work fine to connect it to one side of the heater, try 
> each and see which works best. The alternative would be to use two 20 
> ohm resistors in series across the heater and connect the cathode to 
> the junction between the two resistors.   It should be possible to 
> build an adapter that will plug into the original socket and work with 
> the unmodified circuitry of the transmitter.
>
>       Bruce Gentry, KA2IVY
>
> On 2/23/18 2:48 PM, Kenneth G. Gordon wrote:
>> I have recently been offered the chance to get a pristine, but 
>> tube-less, BC-375, with TUs.
>>
>> I have plenty of good VT-4Cs here but no VT-25/10.
>>
>> Is there a substitute for this tube which could be used by simply 
>> building a base-adapter?
>>
>> Ken W7EKB
>>