[Kenwood] TS-850S DC-DC Converter Board

[Dr. Gerald N. Johnson, electrical engineer]

There are a couple (I presume aluminum) electrolytics that aren't on the
DC-DC board but essential to its functioning that I'd be highly
suspicious of. The miniature aluminum electrolytic was never really
great to begin with and ages rapidly. Its fairly heat sensitive and very
intolerant of long storage without applied voltage. When I check "new"
ones for leakage and power factor, I reject most. And lately the buzz in
the computer industry is that many coming out of China are blowing up on
motherboards with the first time power was applied. Apparently those
with the best prices haven't been formed or have used poor quality
materials. Perhaps being built in a chicken house has then contaminated
with eggshells.

12 volts in, -6 volts out is a natural application for the 7660 and its
many derivatives from Maxim, TI, Analog Devices, or Linear Technology.
With better regulation that the zener diode provides and more energy
efficient, though one should watch out for RF noise.

On the surface mount board, the failure could as easily be a bad solder
connection as component failure.

73, Jerry, K0CQ
-- 
Entire content copyright Dr. Gerald N. Johnson, electrical engineer.
Reproduction by permission only.