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Re: [TenTec] Centurion 422 Bias Circuit Solved

To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Subject: Re: [TenTec] Centurion 422 Bias Circuit Solved
From: "Bob McGraw - K4TAX" <RMcGraw@Blomand.net>
Reply-to: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Thu, 5 Feb 2009 19:45:09 -0600
List-post: <mailto:tentec@contesting.com>
Can't see how you get that date/data from those numbers.

My translation says for SN 5B10053:
5 = May
B = Separator
1 = 1st production for May
005 = 5th unit
3 =  1993 or could that be 2003?

Don't see how you get 34 out of that or 9 as the year of manufacturer since the SN doesn't contain those numbers.

73
Bob, K4TAX



----- Original Message ----- From: "jack" <jfriend31@comcast.net>
To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Sent: Thursday, February 05, 2009 7:04 PM
Subject: Re: [TenTec] Centurion 422 Bias Circuit Solved


according to the tentec code for serial numbers:

amplifier s/n 5b10053

means:

5 = may
b=separator
1=production run for that month
034 =unit number for that run
9=year of manufacture

jack
ak7o

----- Original Message ----- From: "K0BX" <k0bx@arrl.net>
To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Sent: Thursday, February 05, 2009 5:44 PM
Subject: [TenTec] Centurion 422 Bias Circuit Solved


Last night I wired up the cable for my Icom IC-756PROIII to do break-in
CW.  CW keying to the 422, 422 to the rig.

So let me try to explain what I was looking for.

1.  In SSB, if you key the mike with no audio, you get a plate current
of about 100 to 150 ma, 1/2 way between 0 and .2 ma.  This is normal for
SSB.

2.  In CW, using breakin, the older models of the 422 would put the amp
in transmit and draw the 100 ~ 150 ma when it was in between keying.
Like you are waiting for the DX station to say QRZ again.
This would cause a lot of heat from the tubes.  See the QST Review on
the 422 from 1991.

3.  What I found is the later,  models of the 422 that are greater than
the one in the QST Review does not do this.  Instead there is no idle
current in breakin during the pause for QRZ.
I guess I should have waiting to ask the question until I had the wiring
completed.   I had this heat problem with my Drake L-7 and Ameritron
QSK-5.  It would lock the amp in xmit and just go around it for receive
but you
could see the 150ma on the plate meter.

The last question I had was about the serial number and the date it was
built.  From what I have found is that S/N with 'A' in it was before
year 2000.  The last number of the S/N is the year.
So mine would have been built in 1992 and was the 004th on of that
production run.  Any ideas if I am close or not??

Thanks for all the inputs

Joe K0BX

Carter wrote:

k0bx@arrl.net wrote:


I just received a 422 Centurion. My question is: How do I determine
if the newer Bias circuit is installed?? This circuit cuts off the
bias when the rig is in transmit but is in idle.



I think you sort of answered your own question.... if it's in transmit
but idle, plate current should be zero. Going back 10 or 12 years ago,
my bias board failed and then there was about 300 ma of plate current in
idle. You could take it out of its case and check the revision suffix on
the board (see below). Otherwise, I don't believe there is an easy way
to tell.

I had the original bias board that failed; as of ten years ago, I
believe TT  had a -B and then a -C rev of the board.

Note: all of the above is subject to the vagaries of my memory.   <grin>



QSL review from 1994 S/N 10A10091 had the old bias circuit and they
indicated that the newer one had the modifiy circuit. My S/N is
80A10042. But no date of purchase was indicated in the manual. Any
ideas? Any ideas on when the 80A10042 was built?



Probably ask TT.

It's a nice amp! Enjoy it.

73,
Carter   K8VT

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