Western Electric D97464 (field trial 302) project

[WEBellSystemChristian]

So, do you guys think I should rotate the induction coil, to make it look like the original '36s? Would that create electrical problems with the ringer magnet, as Unbeldi stated?

I thought you had already answered that question for yourself:
    My goal is to keep this phone as original as possible to a field trial 302.

Well, I was just wondering if the problems were small enough or unnoticeable enough (or even unnoticeable) that it would be okay to do. If it were a big problem, I would rather make it work properly than look correct inside.

[unbeldi]

I don't know about the problems they had.  The design goals in engineering for a large network like the Bell System, with all kinds of outside plant configurations, service types, and what not... is much different than designing one telephone for use on one telephone line, or your display shelf.   Some of their problems cannot even be replicated on single telephone line connected to modern equipment, because we don't have divided, grounded ringing anymore.

Since the ringer is always connected to the line, coupling between the audio circuit and a grounded ringer could produce line imbalances, which effects crosstalk and transmission characteristics.

I am curious why they placed those coils in parallel in 1936. In the early prototypes in 1932, the D-95137 (wall phone) and the D-95647 (desk set), they did it right and placed the coil axes at right angles, but in the wall phone there was quite some distance between the ringer and the coil, and it may not have mattered.

But it is known from another artifact that ringer performance is effected by the presence of ferrous materials.  When in ca. 1946 or '47 or so, they substituted the steel base plate with aluminum plates, they had to issue specially adapted ringers to compensate (marked with -A date suffix).

I don't think you're going to find much difference in your experience with any configuration, as you either only hear the phone ring and when not, then you talk.  You don't have to worry about parallel transmission lines and such.

[Jim Stettler]

The set I handled had a tag stating return to  Bell labs for service.
Jim S.

Jim, Did your set say Bell Labs, or Murray Hill ?
D/P

The phone belonged to another collector. It said to return to Bell Labs.

I have a 3A field trial payphone that also has a "Return to Bell Labs" tag.

[andre_janew]

I have a 1946 302 and it has a steel base plate.  Must've been the 1947 302 that had the aluminum base plate.

[unbeldi]

I have a 1946 302 and it has a steel base plate.  Must've been the 1947 302 that had the aluminum base plate.

I don't think this was an exclusive change.

[andre_janew]

That would explain why the 5300 series phone I once had had a steel base and a 1952 date.

[unbeldi]

That would explain why the 5300 series phone I once had had a steel base and a 1952 date.

Certainly.  Most 302s had a steel base. It appears that aluminum bases were only used in part for a short period, post-WWII. Some have attributed it to an oversupply of aluminum production as the war demand collapsed, but I have not seen reliable references for an explanation.

[andre_janew]

Have you had any luck finding the 194B condenser or any of the other parts you may need?  Any progress of any kind in the past three weeks?

[WEBellSystemChristian]

Have you had any luck finding the 194B condenser or any of the other parts you may need?  Any progress of any kind in the past three weeks?

I haven't really progressed at all, but I'll try to get some work done on it this weekend.

I've been scouting for the right condenser, but I haven't found anything yet. If anyone finds the same type of condenser that we discussed earlier in their parts or on ebay, please let me know.

I decided not to powdercoat the housing, because the paint isn't really bad looking (I over exaggerated before about the 'bad paint job'), and the finish is correct looking for paints at the time. High gloss is great for other phones, but not right for a piece like this.

I'm not sure how well ABS will hold up under wear and tear for plungers, so I was wondering if there's some way of attaching a piece of plastic or metal to the bottom of a couple 5302 or 500 plungers, in order to make them long enough to work properly? (both fit, but the 5302 ones are longer.)

[andre_janew]

I think that AE80 plungers would be longer yet.  However their smaller diameter would require bushings in the housing to get them to fit right.  Perhaps using super glue to attach a piece of metal or plastic to the bottom of a 5302 plunger would be the best solution.

[andre_janew]

Haven't heard much about this project in a while.  Have you given up on it?

[WEBellSystemChristian]

Haven't heard much about this project in a while.  Have you given up on it?

No, I just haven't gotten around to working on it lately.

It's sittin' pretty on a display table in my room right now. At least it's displayable as it sits now.

[WEBellSystemChristian]

A few updates:

I've decided to strip and powdercoat the housing and base. I figure the powdercoat will hold up at least 3 or 4 times longer than the paint. The longer the powdercoat holds up, the longer the metal is preserved. Because it essentially forms in one molecule, it chemically strips off in one or two pieces.

I found out the hard way just how stubborn paint can be to strip. I tried removing the paint from the outside of the housing with 3 or 4 passes of Rustoleum Aircraft paint stripper, but only got about 25% of the paint removed. The paint on the inside of the housing proved to be much worse, so I had no other choice but to lightly sandblast the inside. The outside of the housing has more delicate curves, so I will be using a drill-mounted wire brush to remove exterior paint. It should be powdercoated in the next couple days.

I'm planning on rebuilding the base, including sandblasting and powdercoating it in semigloss or matte. I already have a ringer cleaned up and temporarily installed. I still need a reversed coil and early, large 194B condenser.

Point is, the project is back on track!!

[Doug Rose]

I can't wait to see the finshed phone.  This was such an amazing find. Are you Still looking for an IV36 E1?......Doug

[WEBellSystemChristian]

I can't wait to see the finshed phone.  This was such an amazing find. Are you Still looking for an IV36 E1?......Doug

Thanks Doug! Visually, it should be finished before long, but I have a long way to go with wiring and finding correct 'guts'.

Nope, I found a III36 version to replace the 1935 E1 I had on it before. It's a lot closer to the I or II original housing manufacture date.

I will also try to replicate the Bell Labs tag on the inside of the phone. Because I don't know the original trial number, and the phone is almost a complete mockup under the hood, what should I put in place of the trial number on the tag (IE 000, 001, 1000, made-up number)? This tag will state in fine print that it's for demonstration only.