Mike Silva wrote:
On Dec 16, 9:58 am, "Rick" wrote:
A few years ago someone gave me a box of tube sockets and some 5763s. I
always wondered if they were any good. So I built up a sloppy little
oscillator, running on 7038 and 22 out of 23 of them oscillated. It takes
17 seconds for a filament to warm up and the circuit to start putting out
power.
Ok so what next? I notice in the tube manual, ARRL handbook 1966, that it
has 13 watts plate dissipation. Wow that seems like a lot for a little 9
pin tube. So I built another stage next to the oscillator and a little pi
network output and drove the heck out of it. Only got 3 watts. Then double
checked the voltages since I was running on a variac and lo and behold I
only had 5 volts on the filament so cranked her up where she should be and
now getting 9 watts into 50 ohms.
Then checked the great W8JI website and see where he put some shaping into
his DX60 to clean up the clicks so I looked at my output with a scope with
my keyer banging away at the thing and ye Gads, a square wave. So now
working on values of a grid block keyer circuit to round off the edges.
Fun stuff.
Added a socket for an 807. Wow, got plenty of drive !! 55 watts out with
600 volts on the plate. 2nd harmonic 45 db down, not too bad. Total money
expended to date - $zero.
Anyone like to do something similar? If you need a 5763 and socket just let
me know. All I ask is you to really use it, not just throw it in the drawer
for some day in the future.
Oh by the way. This is just posted to homebrew, don't need to cross post it
to the other newsgroups, too much of that going on. Pick the group that it
belongs in and they will find it if they are interested.
73,
Rick K2XT

About 5 or 6 years ago I think the government must have dumped its
supply of 5763s since they started showing up by the thousands, 1980s
manufacture. Since as a kid I had seen lots of articles that used
them, I quickly bought Too Many. I think everybody I know has at
least 25 and often 100. Since then I've donated some and sold some
and used some. It's a very nice little tube, and should last forever
(+/-) in oscillator or QRP service.

Very interesting to hear how much difference the lower heater voltage
made. It's tempting these days to just make up a 6.3VDC regulator and
be done with it.

73,
Mike, KK6GM
The 5763 seems to be an original design as opposed to a re-design of an
octal tube into a miniature tube format. I can't find any similar beam
power tubes with a 6.3v .75 amp heater in larger format.
It is amazing just how many miniature tubes are simply re-hashes of a
similar tube in a larger format.

For example, the 6AQ5 is a rehash of the 6V6. The 6BQ5 and 6GK6 are
rehashes of the 6F6 (which itself is a rehash of the 42 and 2A5, and
similar to the directly heated '47). The 6AK6 is a rehash of the 6G6G.
The 6CL6 is a rehash of the 6AG7. I could name many more, and I haven't
even considered the Lockal equalivants either.