[TenTec] power supply trip setup on Century 21

Bob McGraw rmcgraw at blomand.net
Mon Jan 18 11:52:17 EST 2021

Well, I'd say if one does not have or have access to the required 
equipment to align the power supply, setting the correct voltage and 
current trip points, then best one not attempt to perform such a task.

I've repaired a lot of radios  {and made a nice tidy sum of money doing 
so} where attempts to align, tweak, or repair a piece of equipment was 
attempted where proper test equipment or fixtures was not available.

In other words "if it isn't broke, don't try to fix it!"


Bob, K4TAX

On 1/18/2021 9:20 AM, brianpepperdine brianpepperdine wrote:
> Now that I have the PTO restored on my Century 21, I wonder if there is anyone
> who can guide me around the rather obtuse instructions on the TT manual
> regarding setting the power out / current trip setup.
> It calls for large wattage variable resistor (yeah, like we all have those
> sitting all around us) and an ammeter in series. I can say I don't have this
> resistor nor do I likely have access to that sort of thing (not so aptly
> described as it is (not) ).
> I see that they have a relationship between the current trip level and the Drive
> level indication meter on the rig.
> Can I just circumvent this whole thing by hooking up an RF swr meter in line
> with a dummy load and observe a decent power level out from the C 21, say for
> 40m and 20m and accept something around 20 or 25 watts out (that should be
> pretty conservative) as the level of output and then set the determining meter
> resistor at the half or 2/3 scale as the Drive level. That should in theory (I
> think) we well below the danger zone of current draw and allow the trip circuit
> to engage when power gets too high or the feedback circuit is saying too much
> current draw in regard to SWR ??
> Otherwise I really cannot see a way to do it the somewhat zany way TT has it in
> the manual - User parts required that are not user obtainable....
> tnx
> Brian VE3HI  VE3VAW
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