My Kenwood TS870 is drawing too much current. At 50W CW output it is drawing
20A. If I go for 100W it just keeps going up and kills the supply at 25A. Specs
say that it should take no more than 20A at 100W.

This excess current is when the rig is fed into a dummy 50 load as well when
into different antennas when matched to 1:1. The current varies slightly band to
band but only by a couple of amps or so. One clue: on 80M I can detune the
external tuner antenna cap (to 2:1) in one direction and the rig current can be
brought down to 14A with the power out staying at 50W. Under this condition I
can then increase the drive back to a current reading of 20A and get 100W. I can
reproduce this effect on 40 and 30M but to a lesser extent.

It has 2SC2879 finals. Is this a final problem? I don't have much test equipment
or expertise but I suppose I could change the finals if I had to. Actually 50W
is quite adequate for me (only 3DB down) and I have been using it this way for
quite some time with no noticeable differences in the quality of my operation.
Still it bugs me as to what is causing this excess current.

Justa Gess wrote:

What are you measuring the current with?

I'm using the power supply meter, but I have checked the supply meter accuracy
using 2 other ammeters and they all agree.

the power supply might be where the problem is.

And I've tried 2 other power supplies, but still the same rig problem.

Are you getting bad signal reports as in poor quality RF?

All on the air reports have been normal, even after I tell about the problem and
ask for a critical report.

Thanks for the suggestions.

Very expensive classic radio, to "tinker with".
I don't let my nephew (learning) touch my classic car --
but then again maybe it has no value to you - and you are have the money to
buy a TS2000.
http://www.g0sjh.com/Puttenham/hamra..._ts870_PIC.htm

Service manual
http://www.g0sjh.com/Puttenham/hamra..._ts870_PIC.htm

Give Clif a call at Avvid
http://www.avvid.com/

http://home.computer.net/~pritch/raspy.htm
http://www.k1ttt.net/technote/ts870s.html

"Jackson Lake" wrote in message
...
My Kenwood TS870 is drawing too much current. At 50W CW output it is
drawing
20A. If I go for 100W it just keeps going up and kills the supply at 25A.
Specs
say that it should take no more than 20A at 100W.

It has 2SC2879 finals. Is this a final problem? I don't have much test
equipment
or expertise but I suppose I could change the finals if I had to. Actually
50W
is quite adequate for me (only 3DB down) and I have been using it this way
for
quite some time with no noticeable differences in the quality of my
operation.
Still it bugs me as to what is causing this excess current.

"w9gb" wrote:

Very expensive

When I bought the TS870 in 1995 it was expensive, I think around US$2500. But I
doubt it is worth anything like that today.

classic radio, to "tinker with".

If the TS870 is a classic then I'm more ancient than I thought. My idea of a
classic radio has the name Collins, Johnson ect on it. Maybe even my old
Heathkit DX-20 qualifies.

I don't let my nephew (learning) touch my classic car --

I don't blame you not letting your nephew touch your classic car. But don't you
touch your classic car?

but then again maybe it has no value to you

The TS870's only value to me is in fun. And I think I have had as much fun
playing around inside it recently as I do using it.

and you are have the money to buy a TS2000.

Well I could buy a TS2000 but then I would be in the same position I am now
someday.

Service manual

I have the service manual.

Give Clif a call at Avvid

One thing I've never done is to have someone else fix my ham gear. If I can't
fix this I'll modify it. I've already figured a way to feed the TS870 VFO output
to feed a set of tube finals (tube stuff I can fix). Some would be appalled at
that idea. I call it hamming.

Thanks for your suggestions.