[Kenwood] TM-2570A Tx VCO Fixed !

[Tom Anderson]

Paul:

The first 2570s (I've got one #70311XX) had a horrible SWR problem and 
would also cause the heat sink to get extremely hot to the touch. Lean 
on it and you could get a nice red spot on your arm.

With mine originally I could only set the Larsen mobile antenna for 
either 144-146 or 146-148, not in between and cover the entire 2 meter 
band.  Otherwise the SWR protection circuit would cause the power level 
to drop to maybe 30 watts, plus the heat sink got really hot. Kenwood 
finally came out with a mod for the SWR circuit that also cured the 
overheating situation. I believe the 2570 was one of the first high 
power 2 meter mobile rigs(when most were either 25 or 50 watts).  I know 
they also came out with the 2530 and 2550 which were basically the same 
radio, which a few exceptions, just depended on what output power level 
you wanted.  The early 2570s I think were the only ones in the series 
who had the SWR problem at first.

The tech who did the mod for me also found some cold solder joints in 
the rig too.  That rig was nice when I traveled West Texas on business 
as a newspaper reporter.  I could easily hit repeaters 100 miles away. 
 Once in the Dallas Fort Worth area I was driving around and found a 2 
meter traffic net, so I checked into it.  The net control said he didn't 
recognized my call so he asked my QTH.  I told him the small town I was 
in, which he still didn't recognize so I told him I was between Dallas 
and Fort Worth and there was dead silence.  I finally asked him where 
the repeater was and he said San Antonio (250 miles south and no ducting 
either) and I don't think he believed me so I finally just sent him a 
QSL card to prove it.

Tom, WW5L





W0rw at aol.com wrote:

>This TM-2570A was intermittent...
>When it was good it works fine...When bad it doesn't lock up.
>i found a damaged solder joint under L1 on the Control Board.
>The VCO's are potted so there is no stress relief on all those
>components.
>Since the VCO components are epoxied down, the temperature
>cycling from mobile environments has caused
>the lead wire of L1 to pull out of the solder joint.
>It is easy to see under a microscope.
>Paul  w0rw
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