[Kenwood] TS-2000X Final Driver Problems

Sat Jul 5 16:12:29 EDT 2014

East Coast has the 2SC1972 listed as available. Put in the Part Number
Field 2SC1972. They want 85ドル for each one.
Pete, wa2cwa
www.manualman.com
On 2014年7月05日 09:16:58 -0400 "Roger Shultz" <nj2r at verizon.net>
writes:
> 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