JIM HOLSONBACK wrote in a message to ROY J. TELLASON:

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

 RJT> It looks like a light bulb?  Clear glass?  Can you describe anything
 RJT> about the innards?

 JH> Bulb thing is about 1- 1/2" long and about 3/8" diameter. Clear
 JH> glass, with kind of a strip of metal looking thing in there maybe
 JH> about 1/16" wide where you'd expect a filament. It is bent in
a "u"
 JH> shape and maybe total length of that is about 1/2".

Oh!  That sounds like one of those circuit breakers...  I have a few of
them around here someplace that I took out of a Heathkit audio amp I
scrapped out some years ago.  Ever see those light bulbs that flash?  Same
principle,  it's self-resetting,  unless you seriously overload it,  which
it sounds like you did.

We could be pretty sure that was it if that strip of metal was not one
piece,  but two,  with some slight overlap between them.  If you can look
closely at that point and see a gap,  that's your problem.

 JH> (ed. note -  since you don't seem to know about the kind of unit 
 JH> I'm talking about, you're maybe working toward some sort of a 
 JH> consolation prize)



 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.

 RJT> Good question!

 JH> I probably won't hold that one against you - - after all, lots of 
 JH> "all American five" radios worked ok with only a single wave 
 JH> rectifier. BUT -  I still would like to know how these bulb 
 JH> rectifier things with only two leads work.

From what you say up there I'm beginning to doubt very much that this
device is a rectifier.

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

 RJT> Cheap and simple -- get one of those 25A bridges from radio shack,  and
 RJT> bolt that puppy to some metal to draw off heat.  I have one PS I built
 RJT> for a bench supply,  uses a 4A transformer and a 3A regulator (TO-3
 RJT> package),  but the original "6A" rectifier didn't last. 
So I put one
 RJT> of those heavier-duty units in there.  I shouldn't ever really expect
 RJT> RS stuff to meet their specs,  but it's awfully convenient sometimes.
 RJT> :-)

 JH> I'll have to post a circuit diag of the thing and do some more 
 JH> study before I invest to put a bridge rectifier in place of a 
 JH> single wave job. Sounds like new bridge, heatsink, hardware and etc
 JH> would now cost maybe $10? Mayhap too much of an investment in this
 JH> oldie.

Maybe,  maybe not.  I know that I have some chargers here with bad diodes
(you wouldn't believe how cheesy they're made,  and how poor the coupling
was to what they were using for a heatsink -- basically a flat bit of
aluminum),  and I'm probably going to repair them in that fashion.

 JH> IMO, buying at RS is convenient, but expensive, kinda like buying a
 JH> large bag of potato chips at a convenience store -  pay maybe 3x
 JH> too much, but instant gratification..

Exactly so.  They're all over the place.

 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 charge
 JH> on that there lead acid battery, but I blew it up and 'let some
 JH> smoke out" when I tried to crank the mower while this makeshift
 JH> "charger" was still attached.

 RJT> Heh.

 JH> Yep.  I was in a hurry to get that mower restarted, and made a big
 JH> mistake.

 RJT> I have a number of battery chargers around here that have bad diodes,
 RJT> probably from similar causes.  Though a number of them seem to be rated
 RJT> for surges of a LOT of amps for fairly short periods of time (30
 RJT> seconds or whatever).

 JH> No rectifier bulbs in there?  Best I can tell, these bulb types
 JH> were superseded by the Selenium type rectifiers by late 1950's to
 JH> 1960. Maybe before your time?

Seleniums I remember,  cook one of those and that's a smell you never forget. :-)

I've also seen lots of references in older books of mine to copper oxide
rectifiers,  can't say I ever ran across one.

 RJT> Speaking of battery chargers,  this reminds me of one that my
 RJT> grandfather used to have.  The rectifier in that one did look like a
 RJT> light bulb,  only it also had a wire coming out of the top.  That was a
 RJT> mercury vapor rectifier,  and I haven't seen one of those since I was a
 RJT> kid.

 RJT> If that's what it is,  good luck in finding a replacement.

 JH> AFAICT, that was the Tungar type which Tom W. mentioned.  3 leads
 JH> min. Tungar was just a trademark name, by GE or somebody.  Pix of
 JH> those old types fairly easy to find with google search on Inet.

The one I'm thinking of had a base like a regular screw-in light bulb,  but
in addition to that it had a single wire coming out of the top,  about the
thickness of one of the pins on a miniature tube,  but somewhat longer.

 JH> With a little research, I see that there was another kind, with
 JH> tungsten filament and Argon gas, but I still haven't found how any
 JH> of those may have worked with only two leads exiting the bulb, or
 JH> if that is what is/was here.

Let's see if what I wrote above gets us any closer to what's what.

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