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The schematic (in Rider 1-1) calls it a "B power adjusting lamp" but I think it is really a current limit when the unit is first turned on, and the rectifiers look like short circuits. They need a little time to form. I don't know what the electrolyte was, sodium phosphate perhaps; the early ARRL Handbooks have instructions for making electrolytic rectifiers and mention a couple of possible formulations. At best, these things were messy as the electrolyte tends to creep over the top of the jar.
Thanks, Alan! Nice to see you here (I'm the guy who bought that FADA neutrodyne from you).
Your explanation does make sense. It would take time for the current to start building up if it has to pass four sets of liquid rectifiers.
It seems this may work like the in-line light bulb I use when first turning on an old radio.
I also noticed while looking at the book by Ron that there were a couple light bulbs poking through the holes in some of the other battery eliminators.
Technology sure has changed!
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Did you ever get the panel to fit the cabinet?
Electrolytic rectifiers work on the same principle as electrolytic capacitors, except they're intended to pass current in the "wrong" direction and are made to dissipate the heat produced. They went out of fashion very quickly.
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There is an article on the restoration of these devices, but I don't remember where I saw it! It might have been in an AWA publication. The article also described the appropriate solution for the electrolyte. The problem is cleaning out the residue without having to remove the metal caps. Here is part of an article on how they work.
http://www.thorneyhill2.freeserve.co.uk/metalrec.html (no longer works)
In 1920 it was already common knowledge that rectification of AC could be obtained by passing current through a circuit made by immersing an aluminium plate and a lead plate in a solution of ammonium phosphate or sodium borate. It had been found that when this was done a layer of oxide formed on the aluminium plate which then acted as a "valve" to the passage of alternating current in the circuit. Not only simple half-wave rectification was possible but full wave rectification was also achieved through the expedient of using two aluminium plates with the lead plate in between. For these "electrolytic" rectifiers, it had been found that some 60% efficiency was obtained, the other 40% being dissipated as heat. Future development had been forecast at the time, through cooling the aluminium plates, but because mercury vapour rectifiers were then the better option, the impetus of further experimentation leading to new devices was not a priority.
I tried unsuccessfully to restore one of these Philco supplies. Mine was a combination A and B eliminator. The large A rectifier was missing (really a wet-cell charger). The supply originally had a 6 volt wet cell inside. I could never get the cells cleaned out through the small hole in the top. I may jump at a more complete unit in the future and try again.
You see single cells listed on eBay all the time - usually listed as BATTERIES.
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Ammonium phosphate, that sounds right.
Nice cabinet, unusual to find a radio in quartered oak. My 2x2 file cabinet that I use for a desk here, is quartered oak, old office furniture.
There's no obvious reference to this in Lud's index to AWA publications but I do recall reading such an article somewhere. 20 years back maybe?
DaveMc & Alan...thanks for the additional information on the ammonium phosphate and sodium borate. I was able to clean the cells out pretty much fully. I used repeated applications of hot water and a little dish detergent through the fill hole. The cap that holds the electrodes to the bottle appears to be crimped on so I did not try to force it off. There is what looks like a very large square can capacitor inside. It had a burnt label that said "igRad CONDENSER". One lead was actually burnt. I replaced that. I also replaced the crumbling power cord. I don't hold out much hope for this unit but I will give it a try (very slowly) after finding a suitable electrolyte.
Alan...thanks for looking at the old oak cabinet. It looks nice. I just have to give it a function now.
I finally tested the Philco Battery Eliminator. I made a supersaturated solution of Borax and placed it still warm in the 4 rectifier bottles. When I applied power (through a variac) I got only a short dull glow out of the light bulb before the current started to pass through the cells. I could see which cells were working best by noticing the bubble rate. The measured voltages were a bit disappointing: B+ Detector-.60 v; B+ Power - 4.5-6 volts; B+ Amp - 4.6 volts; and B-, -5.5 volts. The bottles did heat up a little beyond when I started. The most difficult part was getting all the Borax out later. It all came out of solution rather quickly (even while current was going through it) and solidified on the bottom of the bottles. It took a bit of hot water and a long screwdriver to get it all out. I'm happy now. The unit will sit on the floor under an old Electrola.
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Just a guess, that the borax had less conductivity than the original electrolyte, so there was more voltage drop in the cells.
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