[TenTec] power supply trip setup on Century 21

Mike Bryce prosolar at sssnet.com
Mon Jan 18 11:33:17 EST 2021


here’s the condensed method I use to set the overcorrect trip

place the C21 into a dummy load with an accurate watt meter
Go to 20 meters, middle of the band
Turn the current trip trimmer all the way counterclockwise (If I remember) 
Key the rig and adjust the drive for about 35-40ish watts RF into the dummy load
Adjust the trip trimmer so the rig shuts down, then back the trimmer off a bit.

IF the power supply trips as soon as you key the rig, reset the trimmer all the way clockwise. Then repeat the test

The idea of course is to trip the over current protection should there be excessive current drawn by the PA transistors. However, one must understand that you can have a high swr, but not draw enough current to trip the OCP circuit.

But that’s how I do it.

Mike, WB8VGE

> On Jan 18, 2021, at 10:20 AM, brianpepperdine brianpepperdine <brianpepperdine at sympatico.ca> 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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