Philco 90 Dial movement - Printable Version
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Philco 90 Dial movement - Guest - 10-02-2008
After restoiration, my Philco 90 works very well. However, the dial is a little slippery. This is because the rubber roler that makes it turn is worn. I tried to adjust it, but it continues to slip a little sometimes, especially near the lower frequency end. Is there any paint or rubber coating I could use to make the metal wheel adjust better to the rubber shaft?
Thanks
Re: Philco 90 Dial movement - Chuck Schwark - 10-02-2008
Try replacing the rubber roller with a piece of similar thickness rubber hose. The old rubber has dried, shrunk and hardened. It cannot be brought "back to life."
Re: Philco 90 Dial movement - etech - 10-12-2008
Quote:After restoiration, my Philco 90 works very well. However, the dial is a little slippery. This is because the rubber roler that makes it turn is worn.
I am curious about this. I have two of those Philco 90 chassis and I don't remember seeing any rubber roller on either of mine. Mine seem to be metal on metal. Were some of them constructed differently?
Ed
Re: Philco 90 Dial movement - Ron Ramirez - 10-12-2008
I've never seen a Philco 90 that used any rubber in its dial drive mechanism.
These sets, as well as Models 20, 35, 36, 46, 50, 51, 52, and 70 use a friction drive mechanism. It depends on friction between the tuning shaft and the dial assembly to work.
Naturally, being dependent on friction, as the parts wear over the years from constant metal to metal contact, friction is lost; resulting in a dial mechanism that slips.
Philco switched to using dial cord in Models 71 and 91. Not dependent on friction between metal parts, cord drive is more reliable overall.
Re: Philco 90 Dial movement - etech - 10-12-2008
OK, Thanks for confirming this Ron.
Ed
Re: Philco 90 Dial movement - Ron Ramirez - 10-12-2008
This photo should prove helpful:
[Image: http://i326.photobucket.com/albums/k420/mrphilco/90drive.jpg]
Notice the entire lack of any rubber, or dial cord; only metal-to-metal contact.
Re: Philco 90 Dial movement - Guest - 10-13-2008
Thank you very much, Ron...and excuse me for the error! I never dismantled this mechanism and it seemed to me that the roller part was hardened rubber, but now I realize that it is metal. The mechanism in my set is exactly as shown in your photo. Incidentally, in my set, the dial wheel makes friction with a groove in the roller part. Is this intentional or has the groove been formed by friction along the years?
I must say that the dial slips only from time to time. I have found that it works quite well if I press the knob downwards slightly when rotating the dial. So I think I can leave it as it is. It is already in its cabinet. I re-aligned the set with the help of an oscilloscope and now it is better tahn ever. It is amazing how powerful this radio is. It is much better than any of my modern radios, and the sound is very good too!
Thanks to all!
Manuela
Re: Philco 90 Dial movement - etech - 10-13-2008
Hi Manuela,
I too am amazed at the sensitivity and selectivity of these old Philco 90 sets. As you say, they are very 'powerful' sets.
As far as the dial slipage is concerned, there is a groove formed in the roller wheel. Friction is created by the spring that forces the back side of the roller wheel forward. I would check to make sure that the spring is not stuck to the shaft. Be sure the spring is applying full pressure to the roller wheel. Also, if you turn the dial to somewhere between 80 and 85, you will see a mounting screw which holds the shaft bracket to the front of the tuning gang. You could try loosening that screw and then apply a slight amount of downward pressure on the knob shaft as you retighten it. If that fails, you could try cleaning any grease off of the dial wheel and apply some rosin to it to create more friction. Rosin can be purchased at a music store, as it is used to 'rosin a bow'.
I'm sure Ron or some of the others may be able to offer some additional advice on how to solve that dial slipage problem.
Regards,
Ed
Re: Philco 90 Dial movement - Ron Ramirez - 10-13-2008
Ed - I think you have pretty much summarized it all.
Re: Philco 90 Dial movement - Tim Tress - 11-13-2008
I successfully repaired the dial mechanism on my 90 cathedral. The hole in the bracket was worn, causing the spring behind the pinch disc to tilt the shaft up slightly. This caused the mechanism to slip. From the junkpile, I found a piece of quarter-inch ID brass tubing, part of the dial on one of those 1940s single-knob Zenith sets. I reamed the hole in the bracket big enough to fit the tubing's OD and soldered it in place, then cut it short enough so it wouldn't interfere with the knob. A drop of oil in the bearing, and it was as good as new.
If you have to do this repair, the rivets in the bracket will have to be carefully drilled out.
Tim KA3JRT