Crawls Backward (When Alarmed)

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Almost Done: Hickok 288X Signal Generator Restoration

Tracking down the rotors that were shorting against the stator in the tuning cap was fairly straightforward.  I used my DMM to determine where in the rotation the blades began to short. 

I just set the DMM to beep when it had continuity, and then put one lead to the stator and one to the rotor, then I turned the frequency knob.  About halfway through the rotation I got a beep, so I knew it was there that something was touching.

Now it's a matter of eyeballing the rotors to see where the problem is.  It's hard to photograph this, but I took a shot at it.

Two things: first, you can see the rotors engaging into the stator (red arrows).  If anything is obviously making contact, it may be visible.

Second, the rotors should more or less be the same distance apart.  The green arrow shows a rotor that is further from the rotor to its right than it should be.

It's easy enough to gently bend the rotors back into alignment.  In my case, I straightened a couple of them out, and the generator now goes to the lowest frequencies as it should.

Now (finally!), I can tidy up the tap that goes to the frequency counter.  I just need to shorten the 470pf capacitor leads, ground the braided shield from the cable, and shrink-wrap everything.

And here it is.

The shield goes to a tab on the frame of the tube socket that's riveted to ground (red arrow).  And the center lead goes to the mica cap, which goes to pin 1 of the tube.

There's an access hole in the cover for the coils right near where I made the connection.  I stuck a grommet in there and ran the lead through it.  One of my rules for modifying old gear is to make it unobtrusive, and to make it reversible.  I also avoid drilling into a chassis unless it's absolutely necessary.

This worked out well.  It could all be undone in 5 minutes.

I took out one of the ground lugs on the front panel and ran the cable through that.  Perfect fit.

I tried a couple of different 6C4s (the oscillator tube) until I found one that would oscillate all the way up to 110 Mc.  In this shot, the counter is reading 110.92730 Mc.  (The leading "1" is not visible - the counter has an "overflow" LED indicating it's at 100 meg or above).

It's stable until about 105 Mc, and then gets a little flaky, but should be fine for radio alignments.  The only time I'll need it that high will be for the highest band on the FM broadcast scale.

I need to epoxy the frequency dial scale into the escutcheon.

While the epoxy is setting, I work on cleaning up the knobs on the front panel.

Real close to being done!  FINALLY.

 
 
 
 

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