>
>Rich said:
>
>"? As I understand it, the larger anode cooler diameter limits it to two
>3cx800s. The larger coolers also requires moving the sockets farther
>apart. Since the 78 has no tuned input, I would consider using 4cx800s
>in AB1. "
>
>The 76 only has 2 tubes and that requires moving one socket. However, the
>76PA and 78 uses 3 tubes and requires no socket moving.
? Thanks for the heads up.
> The middle socket
>is plugged and it works fine. Only 2 x 3CX800A7 tubes are necessary. The
>power output is limited by the power supply.
>
>Although the 78 has no tuned input, it has a resistive termination that
>absorbs about 2 to 3 db of the sxcitation. That, plus the clean imd specs
>of the 3CX800A7 tube mean that the amplifer is cleaner than most
>transceivers. Distortion does not increase when the amp is used.
>
? The trouble with no tuned input in g-g is that solid state radios like
low
SWR loads.
>Before converting to the 4CX800 tubes, look at all of the safety features
>built into the Alpha 99. I assume that they would not put all that
>protection in if not necessary - which means that a simple tube swap to the
>4CX800 tubes using a grounded cathode design and terminated grid and supply
>of regulated screen voltage in the 78 would be an incomplete conversion.
>
>As far as decrease in value, I think that would only be if the conversion
>was ugly. Sloppy workmanship devalues anything.
>
? Amen, Colin. Done right, such a conversion would be a valuable
circuit improvement.
- R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K,
www.vcnet.com/measures.
end
--
FAQ on WWW: http://www.contesting.com/FAQ/amps
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
|