[Kenwood] TS-850 Erratic Power out..NOT DC/DC

[Dr. Gerald N. Johnson, electrical engineer]

First thing I'd do is monitor the negative voltage from the DC/DC
converter and see if its solid while power is changing. I'm still
suspicious of the aluminum electrolytics that are part of the DC/DC
circuit but not on the convertor board.

Then one can only find the trouble by signal tracing through the
transmitter. The fault could be anywhere in the transmitter signal and
oscillator chain. It could be a connection (cleaned by DeOxit is a good
cure), it could be a bad solder connection (I found that in the VFO of
one of my TS-120 a couple decades ago), it could be a bad component.

One other technique is to apply freeze mist or some other circuit cooler
to large chunks of the radio transmit circuits to see if cooling
introduces the erratic jumping, then heat with a hot air source (hair
dryer or hot air gun works well) to see if heat cures it. If those tests
work, then you reduce the area cooled and heated until you get it down
to the component and repair or replace as appropriate.

73, Jerry, K0CQ

-- 
Entire content copyright Dr. Gerald N. Johnson, electrical engineer.
Reproduction by permission only.