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Dial Drive
Mechanism Rebuilding for 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 60 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
Yes, the replacement O-rings are round, while the originals were square tires
(as shown in the illustration below). 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 60 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
get on). 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 we 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 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.
Our thanks
to Ed Holland for sending us the following note:
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.
 Return to the Tech Section Index. © 1997-2006, Ron Ramirez. All
rights reserved. Unauthorized duplication prohibited.
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on Philco 16/44 tuning dial drive assemblies at
the Philco Repair Bench website.