[Johnson] VFO Removal

[Ed Tanton]

There is a MUCH better procedure: go in the side and SHORT the resistor 
with a wire. Trace the wire (connected to the now-shorted resistor) and 
plan to remove that wire from that connection. There is a spare lug nearby 
that you can use, depending mostly on how you want to mount your NEW, 5 or 
10W resistor. One end of it connects to the terminal (from which you 
removed the wire-think of it as your VFO voltage source), and the other end 
connects to the (removed) wire (that goes into the VFO compartment-think of 
the VFO compartment as the destination.) Voila!! The heat from the resistor 
is now OUTSIDE the VFO compartment, and that deadly VFO resistor is no 
longer a threat. (There are stories about the results of that very 
failure-prone component-such as a MELTED [!!!] 0A2... etc. etc.)

Something I am about to apply (since I am forced to go into my Ranger II 
due to the bandswitch cam-block slipping) is a pair of 5W 50V Zeners in 
series at the point that the wire (going back into the VFO compartment) 
connects to the 'dropping' resistor. This SHOULD regulate the VFO at 
100V  without the regulator tube ever firing. I may have to adjust this 
with some combination of 5W zeners. The plan is for the regulator tube to 
be effectively bypassed, and therefore not be there at all, 
heat-wise/failure-wise. That way I shouldn't have to actually go into the 
VFO compartment to implement this plan-saving all these hassles you're 
reading about. I'm not very good mechanically, and getting into the VFO 
compartment was a real bitch for me-for a while. Take your time, and note 
the nuts on the bottom you'll have to remove-and, as I recall-the 
bandswitch cam shaft. If you DO have to remove the shaft & cam: use a 
permanent Sharpie MARKER to place indexing marks on both the cam-block and 
the shaft (on BOTH sides of the cam-block and shaft)-and be careful not to 
rub them off!

In YOUR case, since you MUST go into the VFO compartment, you can just 
remove the VR tube, and add 105V (I think it is) of 5W zeners somewhere on 
the destination-side of the new resistor, to ground. One 4 or 5 terminal 
terminal strip mounted somewhere there's enough of a screw to mount it to 
would solve our mounting problems. I'll probably have to do the same thing. 
I MIGHT just fasten the zener 'string' well mechanically, solder them, and 
cover them with black shrink tubing. (That last point being what you have 
to do for insulation if you don't mount the extra terminal strip.)


P.S. I plan to TRY and drill shallow holes (for the set screws) into the 
cam shaft-so this darn shaft/cam 'connection' won't come loose again 
(combined with some 'locknut').


73 Ed Tanton N4XY <n4xy@earthlink.net>

Ed Tanton N4XY
189 Pioneer Trail
Marietta, GA 30068-3466

website: http://www.n4xy.com

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