[Collins] 32S-1 grid problem found

[Gerald]

On Fri, 2005-12-02 at 20:02 -0800, Glen Zook wrote:
> The basic grid circuit is definitely different from
> any of the manuals and there is definitely glyptol on
> the solder joints.
> 
> The feed through is located just to the right (when
> viewed from the front of the transmitter) of the rear
> most slug in the tuning rack.  When viewed from the
> top this feed through is virtually hidden by the
> tuning rack.  There is a piece of "sub miniature"
> coaxial cable that comes through a cutout under the
> final tank cage that runs to this feed through.  The
> shield of the coax is connected to a solder lug that
> is held in place by the "nut" that secures the feed
> through to the chassis.  The center conductor of the
> coax is soldered to the feed through.
> 
> The feed through is ceramic (remember, the transmitter
> was designed before Teflon was being used).
> 
> Worse comes to worse I can probably make one from a
> very short section of the center conductor and
> insulator from a piece of RG8/U or RG213/U.  The hole
> is just about that size in diameter (3/8 inch
> diameter).  I will have to go through my "junque box"
> and find a second nut to put on the underside of the
> chassis to hold the "home brew" feed through in place.
>  A nut should cut its own threads in the insulation
> material of the coaxial cable.
> 
> Glen, K9STH
> 
Are you sure its NOT C62? I see that going up through the chassis in the
S-3A book. Nut on the top. I know the schematic shows C62 as a plain
capacitor, but its the same part as C137, C56, C166, and C167. C137,
C166, and C167 are on the side of the PA grid compartment. C137 carries
B+ to the driver, C166 and C167 carry heater power to the PA and driver
tubes.

C62 is part of the neutralization bridge and is infamous for failing so
that it messes up neutralization. In the S-1 manual, all the feed
throughs are +80 -20% tolerance. In the military style S-3A manual, that
still applies to all but C62 which is shown as +/-10%.

In the S-3 manual it shows all the feed throughs have that 10%
tolerance. Shows it to be an Erie SK10066S. 500 volts, 1000 pf.

CPNs:
S-1 913-1292-00 for all the feed throughs.
S-3 says C56 is 912-5232-00 but says C62 is the same description as C56
but is part number 913-4061-00.
S-3A says C62 is still 913-4061-00 or mil number 327029H3M0102K and
shows a different part with wider tolerance for the other feed throughs
on the PA grid box.

The nut is probably a 1/4-40 thread.

-- 
73, Jerry, K0CQ, Technical Advisor to the CRA
All content copyright Dr. Gerald N. Johnson, electrical engineer