[Kenwood] TS-2000X Final Driver Problems

Sat Jul 5 09:16:58 EDT 2014

A friend got all excited to work the VHF contest 2 weeks ago and found he
had no output on 2 meters nor 6 meters. He gave up disappointed but asked me
if I could look at his radio to see what was wrong. He had contacted Kenwood
who said it was probably a driver.
I've checked it out and indeed it seems to be the Q3 and Q4 2SC1972's that
are bad but a few other things don't seem right too.
The DC voltages are correct on Q2, the 2SC1971 but the RF levels are much
higher than expected.
Base is about right at 600 mv though spec'd at 450 mv, Collector is 8 volts
p-p spec'd at only 2.5 volts p-p WHY?
On the bases of Q3/Q4 I see 2 volts, spec'd at 1.4 volts p-p and Collector
150 mv spec'd as 6 volts p-p.
Now the DC readings for Q3/Q4 are supposed to be 0 in receive and .74 vdc in
transmit but I have 3.1 volts dc in both conditions. Collector voltage is
correct at 13.8 vdc.
I see a couple other questionable parts as well. D2, a thermistor seems to
be shorted. Someone replace F1 with a "hay bailed" glass fuse with leads.
Presumably that someone had replaced Q2 before and was none too neat about
it so what else may be wrong is a mystery.
I have not had much luck locating 2SC1972-26's yet at either PacParts or
East Coast Transistor or the usual suppliers. Any thoughts other than eBay
China?
Thanks in advance for your thoughts on the above.
73, Roger, NJ2R