[Milsurplus] RS-6 on the air

[Hue Miller]

----- Original Message -----
From: "Kenneth G. Gordon" <keng@moscow.com>

> > The dual section oil cap in the RA-6 only lasted about 30 minutes and
then
> > spilled its guts, I had to replace it with an electrolytic.  The 5 uf
single
> > section cap seems perfectly happy though. The original 6X4 in the power
supply
> > could have shorted and taken the cap out, or the other way around. But
either
> > way, with a new cap and 6X4 it seems OK now.

As i have pointed out in previous posts, this first filter cap is the prime
failure mode
of this radio set. It's just too close to the power voltage-dropping
resistors (don't
have a schematic before me now). I truly believe anyone contemplating using
this
radio should replace this cap first -because it is not a good use of your
time, probably,
to be cleaning oil out of the radio. I think best to: move this cap
elsewhere in the
radio, even giving up stowage space if you move it to a storage area; or,
remove
it altogether, and deal with a little less power - and less heat - but this
approach
causes the receiver B+ to fall too low to fire the voltage regulator tubes,
so if you
go this route you will have to paralled the receiver dropping resistors to
bring the
receiver voltage back up.
However, to repeat, running these as-is is asking for trouble, the oil
inside that first
filter cap will be boiling, just waiting to force itself out!

> > The pops in the headphones on key up were pretty annoying and tended
> > to confuse me when sending, especially on a series of dits(like 7s, Vs
and Hs)
> > Do other RR-6 receivers sound this way? I had to disconnect the
headphones while
> > transmitting.

One of the changes in the RR-6A, besides the tuning range change, moving the
high
end up to 22 MHz and the low end up to i don't recall what, is that the
headphone
circuit has in one leg, two diodes, back to back in reversed polarity to
each other.
I *believe* this is to offer some threshhold resistance to lower level
signals such
as the sidetone and keyclick, by being virtue of the knee voltage or barrier
voltage
effect.

Now, i have not used an RS-6 in about 20 years - but if i recall, the key
sidetone
is delivered by some kind of alligator clip thing to the headphone lead? I
too seem
to remember that the key sidetone, which comes from a neon bulb relaxation
oscillator, does it not, didn't seem too ideal in either pitch or (mostly)
volume. I think
the volume level problem could be reasonably solved by inserting some
resistance
into the jumper that carries the sidetone over to the headphone lead.
Hue Miller