[radiorich]

Hello Howard ,
Anyway I am glad you got the issue narrowed down and hope you get the part you need !

Sincerely richard

[morzh]

If I were too design that (I mean I woulbe told to use ball gear or be fired), I would machine a ball with a small pin at the end, drill a hole in the shaft (concave) and glued the pin in the hole. That would be unbreakable. Better yet, just drill two holes, in the shaft and in the ball, and use separate pin.

[rfeenstra]

Yes, it is a mystery.  The Scott drive is definitely larger, making it easier to machine out of one piece. Philco's is so small that I presume they felt they needed a hardened assembly, hence the ball bearing.  I machined the one for the Scott but I doubt I could do the one for the Philco!  I have a couple of these 38-116 (or maybe they are 37-116's) chassis.  I hate to break them up by robbing parts.  Perhaps you need a complete chassis!? 


Morzh - I would have just machined it out of one piece and then hardened it!

[RodB]

Rob, any light as to how the whole assy is kept together?

[HowardWoodard]

Hi Ron.  That pin holds the coarse shaft in place.  If the coarse shaft can't move, then it's three ball bearings prevent the vernier shaft from coming out.  So I guess you could say it holds the whole assembly in place.

[HowardWoodard]

I may end up buying a whole chassis + shipping just to get the shaft -- no pun intended. -- because at the end of the day, the cost is peanuts vs what it would mean to my family. Personally, I like to keep things in use as long as possible and then out of the landfill as long as possible, so I assume I could turn the chassis into a parts donor after using the tuning shaft.

It cost my brother $148 to ship the 37-9 to me here in the Seattle area. What would you want for your chassis?

Something to consider for sure.

[rfeenstra]

The outer housing has a hole in the side where a pin fits loosely (removable with a strong magnet, or in this case striking the unit on the side so that inertia would pull the pin out.)  This pin rides in the groove you see on the brass part with the gear on the end.  The fine tuning shaft is held in by the 3 ball bearings that ride on the ball bearing on the end of the fine tuning shaft.  That's why that little ball has to be strongly secured to the end of the shaft (how they did that is where our mystery is!).  To assemble this thing, you need to push the fine shaft in to compress the spring so that the 3 balls can be inserted all the way to the narrowest part of the groove.  This allows the brass shaft to be inserted into the outer housing.  Once the 3 balls are inside the outer housing, you can release the pressure on the fine tuning shaft and the 3 balls will expand outward and ride on the small ball on the end of the fine tuning shaft. Then you need to get the groove lined up with the hole and insert the pin.  The pin will hold the brass shaft in place.  The pin could fall out since it fits loosely.  It is held in place by another assembly that turns on this outer housing.  A fairly complex assembly as you can see by looking at the diagram that Morzh posted!

Since I had this unit apart, I cleaned it all up, re-lubed it, and assembled it with masking tape around the outer housing to hold the pin in. I should reinstall it in the radio chassis before I forget how the whole thing goes together!!

[rfeenstra]

This is not the place to buy or sell!  PM me.

[HowardWoodard]

The possibilities of finding one may be greater than I thought.

Hints & Tips #33 ( Philco Service Hints & Tips, Number 33 ) says...

In the 1937 and 1938 model years, Philco introduced a line of high-end radio models that had the new Automatic Tuning Dial and the Cone-Centric Dial mechanisms. The models in 1937 were:

Models:
37-9, 37-10 (Codes 121 & 125), 37-11 (Codes 121 & 125), 37-116 (Code 122 only)
37-675 (Code 122 only) and 37-690
and in 1938:

Models:
38-1, 38-2, 38-3, 38-116, 38-690.

Philco Automatic Tuning

[MrFixr55]

Hi Howard,

You could try to degrease the heck out of the shaft and single ball bearing, rough up a small section and use J-B Weld epoxy. Alternatively, just solder the 2 shafts together or glue the 2 knobs wth contact cement or auto emblem glue. This would allow you to disassemble the unit if a suitable replacement is found. You will have no fine adjustment, but you could tune the radio easily enough without it.

I can't remember, but you said that this set had 2 6a8s? This is rare, as a 6A8 is a "pentagrid convertor". I can't remember if I am repeating myself or if I posted this in a different thread. This set was likely heavily used in the WWII years where consumer electronics and consumer electronic parts were not available due to all factory production shifted to the war effort. Therefore, many substitutions and "hacks" were made. RCA, GE and Philco all published tube substitution guides to keep these sets running during the war.

I may have stated in this or another post, but I am always a fan of getting the audio section to work and putting in a radio - aux switch. Not only a "divide and conquer" troubleshooting technique but allows the injection of MP3 or computer audio of period (WWII era) broadcasts directly without the distortion of modulation / demodulation.

BTW Howard, I forgot to mention this in welcoming you to the Phorum. I have no formal education in electronics; my BS Degree is in Medical Technology. However, I taught myself electricity and electronics. I broke my first TV at the age of 3 and fixed my first TV at the age of 10. As a kid, I loved taking things apart and fixing them instead of sports and other Kid activities. One of my most treasured Christmas gifts from Dad was the US Navy "Basic Electricity and "Basic Electronics" courses written by Van Valkenberg, Nooger and Neville, printed by John Rider Publishing. IMHO, Must reading, especially to help understand the thought process behind these radios from about 1935 to the end of the vacuum tube era.

Below is a link to Volume 2 of this text, covering AF amplifiers, via the "World Radio History" website:
https://www.worldradiohistory.com/Archiv...nics-2.pdf

Hope this helps.

[HowardWoodard]

Hi and thanks. I tried the KwikWeld epoxy process, but it didn't hold, just not enough surface plus it's always hard to glue spherical objects, especially with finished and hardened surfaces. I'm gonna try silver soldering it next week. Might be the same problem. I'm still holding out hope that I'll find a good shaft, whether part of a larger assembly or not.

No, it doesn't have 2 6A8s, just one.

I always appreciate help.

[morzh]

Nothing is going to hold it the way it is; I also doubt it could be soldered. It is polished hardened steel that does not lend itself to soldering very well.

If you want to increase the adhesion, you should attempt (and I am not sure how to do this with objects this small) roughen the surface of the ball, and, desirably, the surface of the convex.
Perhaps an adhesive exists that would do it without roughening, but I do not know adhesives that well.

[HowardWoodard]

Thanks.  I haven't a clue how I can rough up the surface of the steel ball.  Maybe with a diamond cutting wheel on my Dremel.  The convex is already pretty rough.

Under a microscope you can see a ridge of some kind of residue on the ball from where it was in contact with the top ridge of the convex end of the shaft.  Maybe there was some kind of electrical welding used to manufacture the completed shaft.

I'm still hoping to find a replacement shaft.  I have a lead on what might turn out to be a parts donor.

[morzh]

Yes. And you want only the lower part roughened, AND below the equator: the equator and some part between the roughened surface and it should be smooth.

[HowardWoodard]

I think I found a replacement. My daughter picked it up down in Indiana over the weekend and will be shipping it to me.

Fingers crossed.