[Kenwood] TS940 power supply problem?

Tue, 30 Jul 2002 12:52:22 -0400

I just received my '940 from Kenwood East last week.  I sent it to them in mid
April.  From my conversations with them, it appears they've gotten quite a few
'940s lately.

From the postings I've read, it appears that there are a lot of '940s with this
power supply problem.  Mine had the same thing.  Just one day - poof - and the
smell of burnt electronics filled the air.  I received a bag of parts that they
replaced, included was a transistor (I assume it was a pass transistor).

I wonder why '940s are having this power supply problem now?

Its a great rig, but I wouldn't buy one used again (I purchased mine a year ago
from AES).  Seems like there's some flaw in the power supply that's rearing its
ugly head now.  Hopefully with this fix, it'll be good many years to come.

Mark, AA4MF

-----Original Message-----
From: [email protected] [mailto:[email protected]]
Sent: Sunday, July 28, 2002 1:57 AM
To: [email protected]; [email protected]
Subject: [Kenwood] TS940 power supply problem?

Well, I appear to be having trouble with the power
supply on one of my 940's. I replaced the pass
transistors with MJ802's and initially it looked
like that had solved the variation in VC, but after
letting it run for a while, the voltage will increase
if I turn the power control lower. Given the headroom
of the MJ802's I have trouble believing that I have
blown them again, and in any event, I need to find out
what caused it if I did. 

I see there is a service bulletin suggesting a 22k resistor
between the collector of Q1 and ground, and a 4.7k resistor
between the junction of R7/VR1 and the base of Q2. Has
anyone done this mod? However, this mod is apparently 
for voltage increases while in receive mode, and that
does not seem to be my problem. I only see the variation
in Transmit.

The voltages at the various AVR connectors seem to be
ok. Any thoughts???

cheers, Paul - VA7NT ex VE7CQK - email: [email protected]
"Those who hear not the music. . . think the dancers mad."
- - -

Your moderator for this list is:
Larry Wilson KE1HZ [email protected]

_______________________________________________
Kenwood mailing list
[email protected]
http://mailman.qth.net/mailman/listinfo/kenwood