Applies to: Model 16 (Codes 121, 122 & 123), Model 34, Model 44, and Model 144 (Code 121)

The process of rebuilding the dial drive mechanism in PHILCO Models 16, 34, 44, and early production 144 sets is actually quite simple. The dial drive in these sets are friction driven and operate with two rubber tires, as shown in the picture below. Two speed tuning is made possible in these models by pulling out and pushing in the tuning shaft. When pulled out, the sets tunes slow; when pushed in, it will tune fast.

Problems occur when the rubber drive tires become dry-rotted after 70 plus years of use. When this occurs, tuning of the receiver becomes impossible due to the rubber becoming hardened and shrunken, and no longer making the proper contact with the dial drive shafts.

The problem is easily remedied as follows:

Go to a large hardware store and look in the plumbing section for O-rings. Most larger hardware stores stock O-rings manufactured by Danco. You will need two different sizes – number 19 and number 94. Purchase one of each, which is enough for one radio.

If you cannot find the Danco O-rings, here are the dimensions for each replacement:

Number 19 – 1-1/4″ O.D., 1″ I.D., 1/8″ thick

Number 94 – 7/8″ O.D., 5/8″ I.D., 1/8″ thick

(NOTE: O.D. = outer dimension; I.D. = inner dimension)

Yes, the replacement O-rings are round, while the originals were square tires (as shown in the illustration above). However, no worries – the O-ring replacements work extremely well.

With the chassis removed from the set, loosen the two set screws which holds the dial in place on the tuning condenser shaft (be careful – the plastic dial is also 70 plus years old and may be quite fragile). Don’t lose the large rubber ring which is mounted behind the dial scale! Next, the pilot lamp mechanism must be removed. This is held in place by four 1/4″ bolts. Once removed, remove the dial drive assembly from the tuning condenser, which is held in place by two 1/4″ bolts.

It will now be obvious which new O-ring needs to go where. First, remove all traces of the old rubber drive tires (carefully soaking in ammonia will help remove all residue). Next, put the new O-rings in place where the old ones were. The Danco sizes specified above will fit somewhat tightly (but not so tight that they will be difficult to install). You can carefully use super glue when installing the new O-rings if you wish, to insure they will remain in place when the mechanism is operated; although I normally install them without the use of glue, and have had no problems.

Finally, reinstall the dial drive mechanism, the pilot lamp assembly, and the dial scale. Try the mechanism out; it should tune smoothly and the O-rings should not come off when the tuning shaft is pulled out or pushed in.

Read this note on Philco 16/44 tuning dial drive assemblies at the Philco Repair Bench website (as archived on the Wayback Machine).

If you still have trouble:

Check the condition of the large rubber ring mounted behind the dial scale. While these are usually still good, some have been known to deteriorate to the point that they no longer function. The diameter of the ring is critical. If too loose, the dial will slip; if too tight, it will not operate.

Steve Davis writes: I used a gasket from an oil filter to replace the large rubber ring behind the dial scale.

Here are brands and part numbers that I have found so far that should work.

AC PF63
Mopar 04892339AA
NAPA 1372
Premium Guard PG195 PG3387 PG4457
Pronto PO4670
Wix 5137

The Premium Guard gaskets have the largest cross-section and the tightest fit, almost too tight. But, I think any of these numbers will work fine. I’m sure there are other part numbers of these brands that will also work and there may be other brands that I haven’t come across yet. I will keep watching for other numbers.

Ed Holland writes: “Thought you might appreciate a trick I worked out whilst in the process of restoring a model 16 chassis with my girlfriend. I noted from your site that you mention how to repair the slow motion “friction” drives on model 16, 44 & 144. Our drive had crumbled away too, and we found that O rings would fix the smaller parts, but the large rubber ring behind the scale was causing serious problems. It occurred to me to try vacuum cleaner belts, so I found the nearest belt in terms of diameter and thickness, and cut it to the correct width, so that it would fit onto the dial wheel without overlapping and rubbing on the chassis. Unfortunately, it was not quite thick enough to engage properly with the rest of the drive. However this problem was easily rectified by adding a card shim under the belt, all the way around the dial wheel, to expand the belt out to the right size. The result is a dial mechanism that tunes beautifully, without slipping, and was repaired without modifying good original parts.”