Which WD 553/653 Variation Do I Have?

[unbeldi]

I am wondering whether the cover was even on the base originally.  If it was a 533 originally, it should have had its transmitter mounted in the center of the front, yet I cannot see any old mounting holes in the center and it does not seem they could have been in the area of the dial opening, which appears being cut.  Were there 533s with the transmitter in the lower half?

The cover is made from copper, not steel, as far as I can make out, so the base should be copper too.  Is it?   It seems made from steel, judging by the wear around the wall mounting holes.

You are correct...the cover is copper and the base is steel.

I refurbishing it as a 553...I'm using a 2AB dial, 323BW transmitter, 75Z receiver. 

The cover has been stripped, and professionally repainted.  You are correct, the dial hole was hand cut (pretty decently), but the transmitter hole and the hanger slot on the side are WE original cut.  Since 533s had the transmitter in the center, I still have no idea what this cover was originally.  Any other guesses?

In the meantime, I have rewired the base (and yes, it is steel), and it tested it with a 102 wired D2 phone, and it dials/rings; still not sure what it was a part of.

In the core, even the copper units are steel, IIRC.  The copper plating is pretty heavy though. I have seen them only in pairs, when the cover was plated, so was the base. The time period when this was practiced, or the reason, is still unknown to me. Perhaps it was an experiment into corrosion resistant substrates for painting or japanning.

I had examined your pictures about the other cutouts, and also concluded that they looked original, the hookswitch location also has that mounting bracket welded inside, IIRC, which needs more than hobbyist equipment to replicate.
Whence, my surprise ...  I don't see a reason for recutting the dial opening if there was one there before.  Removal of the apparatus blank should have been sufficient.  So there still is a puzzle with this.

The parts you are using are perfectly alright for the period.    The receiver designation, 75Z,  I believe is probably actually the nominal impedance of the unit, rather than the part number. These are stamped on the magnet internally.

[unbeldi]

Ah, I haven't commented about the SC number.  I have seen Signal Corps equipment, that also had the Signal Corps logo, with stamps that looked just like this one, except a different number after the SC. So, I do think this was military equipment, and it's likely that they had professional skilled technicians to perform the conversion. Parts became scarce in 1941 and WECo stopped making new telephones in 1942, at least for the domestic public network.

[extremecinema]

I've noticed that there are different versions of the #20 induction coil... the original large white one circa 1917-18, and another considerably smaller one with a black center coil.  Is there any electrical/efficiency difference in these coils?

[unbeldi]

I've noticed that there are different versions of the #20 induction coil... the original large white one circa 1917-18, and another considerably smaller one with a black center coil.  Is there any electrical/efficiency difference in these coils?

In the late 1910s, WECo replaced the core materials of all induction coils with new silicon doped steel, instead of using bundles of soft iron wires.  The new material had much better magnetic permeability and therefore the coils could be made smaller and were more efficient.  We discussed this recently, and I posted this picture for comparison of the cores, comparing a NO.20 with a NO.46 coil.


Here is the forum link:  http://www.classicrotaryphones.com/forum/index.php?topic=13500.msg141598#msg141598

[extremecinema]

Thank you,  I read that thread.   I recently finished renovating my 553a, and the #20 coil works.  I happen to have a #46 coil in hand.   Would swapping it out change the performance of the 553 in any material way?

[unbeldi]

Thank you,  I read that thread.   I recently finished renovating my 553a, and the #20 coil works.  I happen to have a #46 coil in hand.   Would swapping it out change the performance of the 553 in any material way?

No, not really.  The No. 46 coil was the successor to the 20, and was interchangeable.  The precise impedances of the coil were changes just slightly, but it has very little bearing on performance, especially since you are using the set on a modern line with strong signals.  I would keep the original one.

[extremecinema]

Thank you.