[Chas]

The Gernsback schematic shows two C voltages (4.5 & 22.5). Never saw that before. Also, the battery harness that came with the radio uses 8 connections instead of 7. So many questions for one radio!

The -22-1/2 is for the 120 output tube. That tube has a more open grid structure to keep the plate current in check ,a greater negative voltage is required...

The -4-1/2 is the other tubes, it also goes or should, to the center-tap of the loop. Then to the grid or the RF tube. The loop connections must be clean or there will be noise when manipulating the loop.

With the ARBE-III setting the "A" voltage is permanent and regulated. The BATTERY setting rheostat is used to follow the wear-down of the "A" battery. There should be a reference plate "still" even on an "AC" that recommends where to set the battery rheostat, there should be a cast-in "tick" at 3.3-3.5 one the setting escutcheon. RCA took sets in production and also sent kits to dealers, removing old "DC" data plates was not done, I suspect too "messy"

Those are the facts so, one can choose to bring the battery setting into play, by setting at 3.3 or the "tick" on the BATTERY setting escutcheon with the ARBE it would never be set again. OR dial out or jumper out the battery setting rheostat and set the ARBE-III for 3.3 to 3.5...

The overall filament voltage can be taken from the two jacks on the panel apron. There is an accessory meter that plugs into those jacks and actual supports the entire meter. The correct meter has a pair of swivel contacts, insulated that are rotated for either vertical or horizontal position of the meter. The black meter face has the obvious "RED LINE" at 3.3...

A reminder about the "VOLUME" rheostat... For series filament "AC" that rheostat is considerably higher value. The cartridge is changed. As I said in a previous post I do not know what the resistance is for "AC or "DC" However depending how many tubes when in parallel will determine the correct resistance. For only one '99 is should be around 30 ohms, for two 15 ohms and for three around 10 ohms. If you find you need a cartridge resistance, I'll see what I can find. Failing all else, the cart can be re-wound OR search the WTB.

I did place an WTB in Antique Radio Forum for a jumper strip.

IMHO if one traces the filament circuit and includes the battery setting rheostat, the resistance of the battery setting provides an additional voltage drop and additional bias in doing so. That bias may have a dramatic effect on the sensitivity and overall volume of the set... If you have small children that my twiddle with the controls, choose the safest method that provides results. No harm short term will come to the tubes if operated at 4.5 volts IN THE SHORT TERM, overall long term use (weeks) the emission will fall off at a faster rate than "normal".

The "AC" "battery" harness with the extra wire is to access a portion of the catacomb for the "AC" mode. Should not be in use when operated on "DC".

I took a second look at the "DC" jumper strip ,NO nothing changes in making the one you made, KUDOS.

It has occurred to me that the entire strip could be a PC board fabrication, double sided so circuits can pass with through hole jumpers to combine multiple connections. Holes through the board with contact rings for the screws. There is ample clearance to make the strip wider to account for filament current flow... Since the strip is unseen in normal installation, the "modernization" would not be noticeable.

I kinda wish I had thought of this sooner, like 20 years ago. As it would be inexpensive to fabricate multiples. The circuits could be sealed or not with a conformal coating. Seems all too slick, but my minds eye says it would work a treat. What a blessing for those who find 28 AC and no power supply

So many projects, so little time...

Oh!

Any problems extracting the open audio transformer?  Readers would like to know. Especially dealing with the "nest" of mica bypass caps. All stuck together with rosin...

Do post pix along the way...

Chas