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Tuning Instability: 1936 Philco 60B Cathedral - Printable Version

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Tuning Instability: 1936 Philco 60B Cathedral - KB1PKS - 03-10-2023

I'm seeking help on a troublesome persistence of sensitivity loss and /or completely cutting-out of reception when touching the tuning knob on my 1936 Philco Model 60B Cathedral. Just a little giggle on the variable capacitor tuning shaft can knock out the signal completely, especially on the upper short wave band. Placing rubber grommets and plastic spacers under the variable capacitor helped a little, but not much.
Please see the You Tube video I made at the link below for a visual reference to my issue:
 
https://www.youtube.com/watch?v=f7MoGcZ1Dpw
 
Please, if you've seen such issues before with these early to mid 1930's Philco Model 60 radios and know how to fix them I'd appreciate your help.  Thank you.

KB1PKS  (Bill)

RE: Tuning Instability: 1936 Philco 60B Cathedral - MrFixr55 - 03-10-2023

A few things in general that you should check:

Ensure that there is no oxide on the plates of the variable cap (capacitor) by fully meshing it and running a feeler gauge between the plates.

Ensure that the bearings for the rotor are fully cleaned and lightly oiled. Ensure that any grease in the bearings has not hardened.

There should be a spring clip between the cap frame and the rotor shaft. Ensure that this connection is clean and there is sufficient tension between the spring and shaft.

Ensure that the mounting screws do not protrude sufficiently deep through the cap frame to short out the stator.

Ensure that the frame of the cap is securely grounded to the chassis, preferably by braided wire.

Hope this helps.

RE: Tuning Instability: 1936 Philco 60B Cathedral - David - 03-10-2023

Just watch your video nice set. Cleaning variable caps can sometimes be a pain in the back side. Have had do its more than once. Try taking a flashlight and a lens and look down between the blades might be full on gunk. Mr Fixr55 has given you lots to check might take 4-6 tries to get it good and clean. Good Luck

RE: Tuning Instability: 1936 Philco 60B Cathedral - KB1PKS - 03-13-2023

As suggested by MrFixr55 I cleaned the plates of the variable cap with a feeler gauge, making sure to go through each plate gap when all the plates were fully meshed. Using DeoxIT D5 on a Q-Tip I made sure the rotor bearings were clean and free. I also ran a jumper between chassis ground and the frame of the variable cap making sure any loose grounds were eliminated.  Please see my You Tube video for a visual presentation of the results thus far at the following video link:

[/url][url=https://youtu.be/yvVStOo0LaY]https://youtu.be/yvVStOo0LaY

As one can see in the video, an improvement has been made in stability.  There is less loss of sensitivity and /or completely cutting out of reception when the shaft of the variable capacitor tuning knob is moved or jiggled. However, the tuning stability is still not complete, but it is better. I will continue cleaning the cap and, as suggested I will replace the jumper with a soldered ground wire from chassis to the variable cap’s frame. Thank you MrFixr55.
 
However, as seen, there still is some slight loss of sensitivity when the variable capacitor tuning knob is moved or jiggled. If anyone has further suggestions that may result in better tuning stability I would appreciate your comments and suggestions.  Thank you.

KB1PKS (Bill)

RE: Tuning Instability: 1936 Philco 60B Cathedral - klondike98 - 03-13-2023

I had a variable cap that was giving me fits. I finally took it out of the set, scrubbed and washed it. That finally solved my problem. A better solution is to take it out and use an ultrasonic cleaner on it. Some folks put them in the dishwasher. (you would want to disassemble in trimmer caps and remove the mica before doing this).

RE: Tuning Instability: 1936 Philco 60B Cathedral - KB1PKS - 03-13-2023

Thanks Bob,

But this variable cap is mounted on old rubber grommets that I'm sure I would have to destroy to remove the cap. First I'm not sure I could find the correct size rubber grommet replacements (the elevated height is important for the rotating dial to correctly display in the escutcheon) and second this cap's shaft has a reducing gear drive that I'm afraid might corrode in a water washing environment.  Do you know of other "non-aqueous" ways to clean variable caps in place?  

Cheers,  Bill

RE: Tuning Instability: 1936 Philco 60B Cathedral - Ron Ramirez - 03-13-2023

Renovated Radios has new rubber grommets. They should be replaced anyway.

http://renovatedradios.com/product.php?product=320

If thoroughly dried and then the tuning drive re-lubricated, washing should not be an issue. You could dry it after washing with a hair dryer or heat gun.

Incidentally, the tuning drive uses ball bearings, not gears.

RE: Tuning Instability: 1936 Philco 60B Cathedral - KB1PKS - 03-13-2023

Thank you Ron!

Your advise is always held as paramount!  Do you know who or where I can find the "in spec" replacement rubber spacers /grommets that we will need to remount the variable cap after it is pulled and cleaned so that it has attain the proper height to properly display in the tuning dial in the escutcheon?

The removal and cleaning is something I can do but the proper remounting, reconnecting and alignment may be a function of those with better equipment and far greater expertise than I to ensure success. I really love my old Philco receivers, my 1942-400X, and especially this old 1936 Philco model 60B receiver, and I'm hoping for nothing less than factory prime restoration!

I will copy my friend Kevin to see what he says at Antique Radio Restoration in Putnam Connecticut to increase chances for success!

Kind Regards,  KB1PKS  (Bill)

RE: Tuning Instability: 1936 Philco 60B Cathedral - Ron Ramirez - 03-14-2023

Quote:Do you know who or where I can find the "in spec" replacement rubber spacers /grommets that we will need to remount the variable cap after it is pulled and cleaned so that it has attain the proper height to properly display in the tuning dial in the escutcheon?

Please see the link I posted in my reply, in post #7 above.

Removal and reinstallation of the variable condenser in model 60 is very easy; nothing complicated about it other than keeping those two-piece rubber grommets in place as you attach the mounting bolts.

Alignment is not difficult either, provided you have a good signal generator. If you don't, then perhaps sending the set to a professional would be a good idea.

RE: Tuning Instability: 1936 Philco 60B Cathedral - KB1PKS - 03-14-2023

Thanks Ron, I missed the fact that you had a link to a vendor that supplies the correct size rubber grommets for model 60's to re-mount the variable cap in your #7 post above. 
I know water can remove the ink that prints the frequency positions on the rotating Bakelite dial.  Can that be removed (and re-positioned correctly afterwords when re-installed) so that the variable cap can be washed in water as suggested by klondike98?

Thanks, Bill

RE: Tuning Instability: 1936 Philco 60B Cathedral - klondike98 - 03-14-2023

Yes the tuner dial face comes off the variable cap shaft with the loosening of a set screw or two. Here's mine from a 60MB restoration. I see in that case I used a rust remover as the chassis was pretty rusty to begin with. You can note where the dial position is when the variable cap is fully closed and then replace it in a similar position when the variable cap is replaced.