The PHILCO Phorum
A Few Model 60 Questions - Printable Version

+- The PHILCO Phorum (https://philcoradio.com/phorum)
+-- Forum: Philco Radio Discussions (https://philcoradio.com/phorum/forumdisplay.php?fid=5)
+--- Forum: Philco Electronic Restoration (https://philcoradio.com/phorum/forumdisplay.php?fid=8)
+--- Thread: A Few Model 60 Questions (/showthread.php?tid=16870)


A Few Model 60 Questions - Winky Dink - 06-23-2017

I spent several days making silicone tuner mounts to replace the dry and cracked original rubber mounts…

[Image: https://c1.staticflickr.com/5/4214/35347930801_8573913a5f_z.jpg]

…and it occurred to me that I don’t know the purpose of the rubber mounts.  They insulate the rotor from the chassis, but then you need a chassis ground for the rotor.  So, what for are the rubber mounts?

And speaking of chassis grounding, this radio has a puzzling way to ground the tuner.  The wire with yellow dots goes from the ground post of a compensating condenser to the ground of a Bakelite block condenser, and then it’s soldered to a tuner-mount screw head.  

[Image: https://c1.staticflickr.com/5/4266/35437400916_68d5347b23_z.jpg]

It appears to be an original wire, but I’m don’t think the factory soldered it to a screw head.  Isn’t the connection from (1) to (2) superfluous?  How was the tuner originally chassis-grounded?

Finally, was the connection to the speaker hard wired, or was there a plug?  

Thanks for your help.
- Henry

RE: A Few Model 60 Questions - morzh - 06-23-2017

The grommets do not insulate: they are to prevent the microphonics.
As you could see there is a metal bushing inside; it will get squeezed between the washer and the chassis when the screw is fully tightened. But the grommet will prevent the cap from rocking and vibrating. It is not an insulator.

RE: A Few Model 60 Questions - Steve Davis - 06-23-2017

The ground wire soldered to the tuning condenser mounting screw is factory. Philco did that on several models.

Steve

RE: A Few Model 60 Questions - Winky Dink - 06-23-2017

Got it. Thanks.
My self-learned concept of microphonics relates to actual movement of vacuum tube components when the tube vibrates. Is that wrong, or how does vibration make a tuner go microphonic?

RE: A Few Model 60 Questions - morzh - 06-23-2017

Anything that is capacitive or inductive and where vibration can change the characteristics enough for it to become noticeable due to the sound propagation whether through air or through chassis can create microphonic effect. Tubes have large electrodes on flexible enough support that they could experience oscillation; so do the tuning caps.

RE: A Few Model 60 Questions - Winky Dink - 06-23-2017

Okay. I'm a little smarter now. Thanks again.