'71 squareback clock repair

[jadney@vwtype3.org (Melissa & Jim)]

>From: JK <jsk2649@osfmail.isc.rit.edu>

>My clock seems not to be working anymore. Do you have any idea how do I
>repair it? By chaning the fuse? I would like to hear out your tips! 

Type III clocks are divided into two groups:

1)  Standard mechanical clockwork, wound at about 1 min intervals by a solenoid.
        a) 6 V, -'66
        b) 12 V, '67-70 (I think)
2)  Continuously driven transistorized (not quartz) clockworks, 12 V, '71-73.
        a) grey face
        b) black face

The early ones can almost always be fixed by just cleaning them up.  They 
need a bit of "sticky" (so it won't migrate away) oil in all the pivots, and 
they often need to have the contact points polished with a small point file. 
 If the points have welded, then the tiny wire fuse will be blown away.  You 
can replace this with a single strand from a piece of fine stranded copper 
wire.  Just solder it back in the space between the two hollow rivets that 
already have solder in them.  I always replace the resistor that bridges the 
solenoid with a 1N4002 diode.  This will eliminate the sparking that causes 
the points to weld, but the diode MUST be put in the right direction: the 
banded end is toward the end of the solenoid that receives the +12 V from 
the contact points.

The late clocks are much more complicated.  I have had a lot of trouble 
getting these to be reliable, even though they should be much better.  In 
general I find that I can get them to work, but they eventually just stop, 
either on the bench or later in the car.  I SPECULATE that there is a 
problem with the transistors that leads them to either become leaky or lose 
gain after they are 10-15 years old.  Otherwise it could just be a matter of 
a poor internal electrical connection due to oxidation after a few years.  I 
would be pleased to hear from anyone who has more insight into this.

Keep in mind that these were never particularly good clocks.  While they can 
be adjusted to keep good time, they are not well temp compensated.  I got 
tired of spending time to adjust them only to find that they were quite 
different outside at 40 F.  Nevertheless, I wish I could keep them going.  
Working over the late style clocks is another of my long term projects.

Jim
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       Melissa Kepner                                    Jim Adney
       jadney@vwtype3.org               jradney@njackn.com
                             Laura Kepner-Adney
                             Madison, Wisconsin
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