[TenTec] Ten Tec Centaur issues

[rick@dj0ip.de]

Mike, it is most likely a tube.

PLEASE TAKE ALL SAFETY PRECAUTIONS FOR WORKING WITH HIGH VOLTAGE.

1)  Power OFF, remove A.C. plug from outlet, wait a couple of minutes, then carefully remove the cover. BEFORE DOING THAT THOUGH, make sure there are no kids or pets in the room with you.  

2)  While waiting for the high voltage to bleed, connect the amp to a dummy load, even if it is just a 100w dummy load.  Bigger is better.  Connect the transceiver to the amp as usual, including amp keying cable(s).

3)  With the Amp 'OFF' but connected as normal, set the transmitter's power output to just 10w carrier output.  I don't mean 10w in "Tune", I mean 10w in CW position.  Switch to SSB and make sure the power is still in the 10w range.  THEN TURN THE MIC GAIN TO MINIMUM. 

4)  BACK TO THE AMP:  Check that no residual voltage is left on the plates of the tubes.  Check voltmeter on amp and then short the top of the plate caps to ground with a long screwdriver.  Don't touch the metal of the screwdriver.

5)  Remove any 2 tubes.

6)  DANGEROUS:  DEFEAT THE INTERLOCK by placing a book or two on top, THEN DON'T TOUCH IT.

7)  Now plug the amps AC connector into the wall outlet and Power the amp ON.

8)  Key the amp without applying power.  In SSB position, simply key the mic and do not speak into it.  Check the idle current of the single tube.  RECORD ON PAPER.

9)  Key the transceiver in CW (applying 10w) and peak amps 'Tune' and 'Load' for max output power.  Should be in the range of 60 to 80w.  Measure and record on paper together with the idling current for that tube.

10)  Power OFF and unplug it's AC from the outlet. WAIT A COUPLE OF MINUTES.

11)  Repeat step #4.

12)  Remove the one tube and lay it aside.  Insert another tube (by itself) into the amp.

11)  Repeat steps 8 thru 10.

12)  Remove the tube and replace it with the 3rd and final tube.

13)  Repeat steps 6 through 10.

You are done.  You now have a snapshot of how each tube is performing.  
Each tube should have reached about 60w to 80w.

Glowing red-orange plates (normally) not a good thing, though you will see some light glowing on current peaks.
HOWEVER, if one of the tubes is bad and you don't know it, in your effort to tune the amp to reach normal power, you are often drawing more power from the 2 remaining tubes than you should be and that is why they are glowing.

NEVER DO ANY OF THIS WORK WHEN YOU ARE TIRED.
YOU MUST BE FULLY CONCENTRATED WHEN WORKING ON HIGH VOLTAGE AMPS.

Gud Luk Mike.


73 - Rick, DJ0IP
(Nr. Frankfurt, Germany)



-----Original Message-----
From: TenTec [mailto:tentec-bounces at contesting.com] On Behalf Of Mike Bryce
Sent: Wednesday, November 09, 2016 10:56 PM
To: Discussion of Ten-Tec Equipment
Subject: [TenTec] Ten Tec Centaur issues

gang..

Haven’t use this amplifier is years, but with the crappy conditions during CQ WW. I fired the beast up.

It wasn’t a good day.

The amp’s drawing too much current. I’m getting RF out, but not like it should.

On 160 meters, 570ish watts into dummy load

80 and 40, lucky to see 312 watts

about the same on 20

and only 225or so on 15 meters

The tube, all of them, have nice red plates———not good!

160 meters, no red plates and current seems to be within limits.

Grid current about 50 ma on all ands

resting current, no drive, 80 ma.

Not an amp person, so up for some clues

I’m Mike, WB8VGE

Mike Bryce
prosolar at sssnet.com



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