Hello, Jasen.  Thanks for responding.

 JH> I ended up blowing it up - - I'll tell about that later.  Took it
 JH> apart, and the only thing in there which could possibly be a
 JH> rectifier is this lightbulb-looking thing, with 2 bare leads out
 JH> of the bottom of the glass, and wired to the circuit board.

 JB> Circuit board, I guess that means it's not old enough to have a
 JB> metal-oxide rectifier stack in it   (looks like a buinch of metal
 JB> plates with a brass rivet throught them and 4 wires attached)

Nope, and actually there isn't really a circuit board.  all the
components, what few there are, connect to an old fashioned terminal
strip.

 JB> That one wasprobably a real light bulb.  they make a handy current
 JB> limiter for trickle chargers.

Nope, in that case also, the bulb-thingie was the only thing there which
could have been a rectifier.

 JH> My questions - -1.  What the heck are these bulb things, and how
 JH> much would a replacement for the unit at hand cost?

 JB> the cost is small, the trick is getting the right one....

I expect they're hard to find now, having been superseded in the market
by the selenium type by about 1960.

 JH> 2.  How can a rectifier with only 2 leads give good enough DC to
 JH> run an auto stereo back in the home, without a lot of hum.

 JB> I don't think it can, keep lookimg.
 JB> trace the transformer secondary circuit, it's gotta go to the rectifier
 JB> or possibly the on/off switch of fuse)

Done, and I'll have to make up a little graphic of the schematic and
post it later - - going out of town for a week, to check out new
grandson in Alabama.  :-).


 JH> 3. Should I pitch the thing, or could maybe some large diode or
 JH> diodes be added, which would make it useable again?

 JB> if it's got a dead lightbulb it needs a new one,  check the one you
 JB> have for clues. for low voltage ones the colour of the glass bead on
 JB> the filament supports indicatees the voltage.

This is not a standard lightbulb.

 JH> FWIW, in desperation, after probs with the riding mower, I used
 JH> this unit for a battery charger.  It worked OK, and put some
 JH> charge on that there lead acid battery, but I blew it up and 'let
 JH> some smoke out" when I tried to crank the mower while this
 JH> makeshift "charger" was still attached.

 JB> you could have cooked the transformer primary, (I reecently did that by
 JB> accidentallt to tow of my plug packs)

Transformer still OK - has 15-0-15 VAC at the secondary.


 JB> OTOH that thing could have a switching reguilator that's been cooked,
 JB> (what all is on the circuit board?)

I'll post diagram later.  There are two small parts there which are
clearly cooked.  The bulb think looks to be OK.  The secondary side just
has those two small parts (now blown), the bulb thing, and a 4000 mfd
capacitor.

- - -  JimH.

... "Bother!" said Pooh, as he saw the sparks and smelled the smoke.
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