Brenda Ann schrieb:

I got 2 S350's and 1 S350DL pretty cheap. Got one of the S350's working (all
three had been reverse polarized on the power, and the protection diodes
were all shorted),

Not a very smart construction there. At 6V supply, a kludge like a
protection diode in parallel should no longer be necessary (much safer
to use one in series). (I once tried operating my Sony ICF-SW30, 4.5V
nominal, with wrong polarity - that plug got pretty hot pretty fast
indeed. Fortunately nothing more happened.) A radio shouldn't go up in
smoke like this with reversed polarity. (Even in the YB400 which is a
little sensitive to that, it's merely the AF amp that dies.)

but the other S350 doesn't power up properly (I have to
input B+ to the input filter cap, and then it will only stay on as long as I
hold the power button), and the S350 DL is still totally dead.

Look what you can find in terms of regulators, maybe the one for µP
supply in the totally dead sample is defective. As for the half-working
sample, this could be a problem with battery voltage detection. For
troubleshooting this, a schematic would be handy indeed.

Stephan
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