[TenTec] Century 21 problem

[Mike Souhrada]

Kb4utv@aol.com wrote:
John
I would not be too hasty on diagnosing it as a drive problem.
Further, the meter may or may not be properly set.

The manual covers this on page 3-28, second paragraph.
Find (good luck) the 2.5 Ohm 100 watt load resister and use an external
meter to measure the actual current draw under load. I found a 5 Ohm
about
50 watt variable in my junk box so I was lucky to be able to do this.
Set the meter first when drawing 6 A. Then adjust the SCR to trip when
operating normally.
I saw the other reply-could be that -not likely; however, it would
explain
the jumping 30-15 watt situation. So would failure of the drive
transisters
or finals.
Remember this unit shuts down when the load exceeds 6 A and that's
controlled
by the SCR circuit.

The 2N3055 should not get "really hot"-
Mike
Le Claire, Iowa

The scr  
> I have a Century 21 with a drive problem.  It is hard to get the full 60
> watts input without drawing to much current from the power supply.  I get the
> hum in the side tone whenever this occurs.  Also when it seems to be behaving
> itself, the power output will flucuate between 30 and 15 watts, never a
> steady output/input, but not a large current pull on the power supply.  I
> checked antenna, coax, etc to be sure I wasn't getting a mismatch.  Am using
> a MFJ Tuner.  I think it might be associated with the power supply.  The
> switching transistor on the rear panel, I believe it is a 2N3055, gets really
> hot.  Could this transistor be the problem?  Looking at the power supply
> diagram, I think this is what regulates the voltage for the drive operation.
> Am I on the right track?  Any suggestions most helpful.  73's  John  KB4UTV
>

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