[TenTec] Johnson PS ??

[Ron Feutz]

Rich,

I tried to reply off-reflector but your email address on QRZ bounces.  I am 
an EFJ dealer and if you can send me a pic or model number I will try to ID 
the PS and will send you a copy of a manual.  I'm not a tech myself but 
have the people to do the job.  The EFJ repeater power supplies are brutes.

Ron - WA9IRV

At 04:17 PM 2/23/2003 -0500, you wrote:
>Hi,
>   Assuming that the P.S. is operating normally; I would use a string of
>silicon power rectifiers in series to reduce the output.  A silicon
>rectifier (any kind) will have a .7 volt drop across it.  Three in series
>will give a drop of 2.1 volts.  16volts minus 2.1 equals 13.9 volts.  Close
>enough to the classic 13.8 vdc.  Or if want add another in series then you
>would be down to 13.2 volts.  I would go with the 13.9 vdc.
>   You did not mention what TT equipment, I assume a 100 watt transceiver.  I
>would use 25 amp diodes at least and mount them on a heat sink.  These
>diodes are very cheap, and check their temperature by hand.
>   Check with JOHNSON or a Johnson two way radio shop for a schematic. Locate
>the voltage regulator and with a change in ONE resistor you could drop the
>voltage.  If you can read the letters/numbers on the IC's. (LM-340, and 723
>are common ones) I might be able to tell you what resistor to change.
>    Check to see if you find any pots.  If you see two, one would adjust the
>voltage and the other the crow-bar point, (voltage above the normal at which
>the PS shuts off)
>    GL and 73   Ken  WA4RPH
>
>    PS.  If you dont know the source of the PS it could be defective and
>discarded by some tech. Safest is to assume it is bad unless proven it is
>not.  Caveat emptor.
>
>-----Original Message-----
>From: tentec-bounces at contesting.com
>[mailto:tentec-bounces at contesting.com]On Behalf Of Rich Gaarden
>Sent: Sunday, February 23, 2003 3:24 PM
>To: tentec at contesting.com
>Subject: [TenTec] Johnson PS ??
>
>
>Hi Folks,
>
>This is off topic I suppose but the PS will be used on Ten-Tec equipment!
>
>I acquired a very heavy 40# perhaps PS which is not properly regulated (16
>V).  I was told it was from a repeater and that it was a Johnson 30 amp
>continuous.  I thought this would be an easy fix.
>
>There are heavily heatsinked diodes. There is a substantial choke and
>appropriate filter caps.  There is a large two section transformer. There is
>a small section which vaguely resembles a VR but there are no pass
>transistors.  Anyone know how this thing might work?  Could it be a
>saturable reactor?  Any one know how to regulate the output?
>
>I realize that I'm not giving a lot of information but perhaps enough for
>someone to point me towards help.  I have worked on a few supplies but never
>one like this!
>
>Thanks,
>
>Rich  KF3DQ
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