[Milsurplus] AT-12 Photo - 814 vs 807

[Richard]

Yes, all true, but you don't have to change the tube socket. Wiring 
changes are not as onerous as construction changes.

RB, AA1P


On 03/08/2017 04:02 PM, Kenneth G. Gordon wrote:
> On 8 Mar 2017 at 15:52, Richard wrote:
>
>> The 814 has a small 5-pin base, the same as an 807, so it's an easy
>> change.  However, the 814 is a beam-power tube, which is not so
>> sensitive to plate voltage, and will probably work fine down to 500
>> volts.  Overall efficiency will not be great when you're putting 32.5
>> Watts in each filament.
> Well, in point of fact, the 807 is also a beam-power tube.
>
> However, the 807 has a plate dissipation rating of 25 watts, while the 814's is 65 watts.
>
> Big difference.
>
> But in my opinion, the big problem is that the 814 is a "filament" type tube with no separate
> cathode, while the 807 has a cathode.
>
> Now, since the 807's cathode is connected to pin 4, and the suppressor grid is internally
> connected to pin 4 in the 807, while the suppressor grid in the 814 is ALSO connected to pin
> 4, substituting the 807 for the 814 may be fairly easily "do-able" but one would have to
> connect whatever is connected to the 814's "cathode" to pin 4 in order for things to work
> properly.
>
> But, since I don't have even a remote clue what the AT-12's schematic looks like, that issue
> may already be taken care of....or not, as the case may be.
>
> In any case, I cannot see how the 807 can be a direct sub for the 814...
>
> Ken W7EKB
>
> ---
>