[Collins] 32S3 loading control

Wed Jul 23 23:30:32 EDT 2008

Smith,

Adjustment of C80 is problematic, and is not likely to yield acceptable
results without compromising the load setting on the other segments that C80
influences. The root of the problem is S5 and the taps on L15. While the
exciter tuning is capable of tuning any frequency in the specified range of
the 32S-3, the emission tuning and load lever are not, because of the
limited L15 taps. This problem also shows up on 17M. On 17M you can
sacrifice the 21.0 band and add a tap for 17M between 1 and 2 turns lower on
L15. I have never been interested in 30M, but the schematic shows that the
unused 3C segment of S5 may allow you to add a tap to L15, again between 1
and 2 turns lower than the 14 MHz tap, and get good results. This mod will
not be for the feint of heart. It is risky to S5, and you obviously have to
remove the PA cage. If you pursue a "proper" fix, be sure to use the same
size buss wire, and be sure to flatten the end soldered to the coil (L15)
just as the factory did to avoid a melt-down of the joint. There is a lot of
RF current at that point.

Several outboard kluge fixes have been published. One of these may be OK.

V/R
Bob KF6BC

-----Original Message-----
From: collins-bounces at mailman.qth.net
[mailto:collins-bounces at mailman.qth.net] On Behalf Of w9hak
Sent: Wednesday, July 23, 2008 3:14 PM
To: Gerald Johnson; CRA Reflector
Subject: [Collins] 32S3 loading control

My 32S3 loading control capacitor is fully meshed when loaded up on 30 
meters. In looking at the schematic it seems that increasing the 
capacity of C-80, 100-500 pf, would help move the loading capacitor from 
the fully meshed position. I have been living with this issue for some 
time. I have to reduce the drive to maintain proper plate current.

C-80 isn't easy to reach and I suspect it was set at Collins during 
construction. Haven't found any information on setting up the loading 
assembly on this transmitter. Therefore I have been hesitant in tuning 
these capacitors. Any insight in the area would be greatly appreciated.

Smith Bradford
W9HAK

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