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ZC1 Flick Tuning Mechanisms

by Chris Underwood ZL2CU

 
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Refurbishing Tuning Dial
 
 
 
 
 

The purpose of the flick tuning function is to permit the rapid selection of up to two different preset frequencies.  Transmit and receive frequencies are set separately.

With the dial unit removed limited access is available to most of the flick tuning linkage.

The photo to the left shows much of the linkage system, to gain full access requires removal of the front panel.

However with the dial unit removed most adjustments and lubrication of moving parts can be carried out.

Most components making up the flick tune linkage system are mounted on the front of the tuning gang mounting frames. 

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Not visible in the photo to the left is the linkage and spring which lifts the fine tune drive wheel away from the dial scale plate when the "Flick" position is selected.  This assembly is fixed to the back of the front panel.

The unit shown in the photo is a Mk-1 VFO module removed from a set undergoing restoration.  The flick tune linkage just requires cleaning and re-lubrication of the sliding mounts.  However the "Flag" assembly has suffered damage to the Red Flag.

Typically this  type of damage is caused when a dial assembly is removed from a set without proper care or full knowledge of the components involved as it is hard to see what's happening.   The set this module came from had been heavily modified, including the circuitry of the VFO, by a previous owner.  

Mk-1 Flick Tune Linking and Flags

Note: The linkage is identical on the Mk-2 and also both TX and RX sections of the sets.
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The photo to the right shows the Flick-Tune Knob assembly.  The key to this component is the flange just below, but forming part of the knob, which pushes on the end of the linkage above causing the lift pin shown in the photo below to lift the "followers" up and away from contact with the Flick set plates when the Tune function is selected.  It also allows a spring activated lever to lift and hold with some pressure the fine tune drive wheel rotated by the fine tune knob against the edge the tuning scale plate permitting the set to be tuned. 

When the "Flick" position is chosen the reverse of the above takes place.  The "Fine Tune" drive wheel is pushed clear of the scale plate and the "Followers" are allowed to rest on the edges of the Flick Set plates.  When the main tuning knob is rotated the "Followers" slide along the edge of their respective set plate until one falls into the notch of a set plate locking the set to the frequency the set plate is adjusted to.  When a follower falls into a notch its associated flag is activated to show which pre-set frequency has been selected.

 

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View of Flick Linkage showing Lift Pin for Followers

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View showing Fine Tune Drive Wheel Lever and Spring Set Up

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Close Up View

 

 

 

View Interface

Close up View Showing Flag Springs and followers

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View of Flag mounting from above

a(note: locating pivot pin for flags passes through front panel of set and is also the marker for the tuning scale)

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The flick tune linkages seem reasonably robust and normally give little trouble, occasional lubrication keeps them sliding freely.  A light grease is recommended. 
  • Note:  Sometimes it is found that fine tuning is erratic with the fine tune slipping.  Although this could be the result of a badly warn drive wheel or scale plate it can often be traced to the fine tune drive wheel not properly engaging the tuning scale plate.   A poorly cast flick tune knob or a poorly stamped or bent fine tuning lever can cause this problem.
    • The diameter of the base of the cast flick tune knob is sometimes too large and even though fine tune has been selected the knob continues to engage the fine tune lever preventing it from lifting the fine tune drive wheel into place.  Carefully filing the excess casting away should fix the problem.
    • Sometimes it may be found that the fine tune activating lever has not been punched out to the correct dimensions and the lever fouls on a tuning capacitor mount attached to the front panel or the cut-out is not deep enough preventing the proper action of the lever in lifting the drive wheel sufficiently.  In some instances it may be the punching of the front panel that is at fault.  If the photo above showing the location of the two fine tune levers, is examined it can be seen that the TX lever partially obscures a mounting hole for the tuning gang assembly.
The Flag assembly once properly set up also operates effectively with little trouble.   However it can be easily damaged or knocked out of adjustment by careless or forcible removal or insertion of the dial assembly.
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The followers are normally held under tension by a small leaf spring mounted above each follower.  Each follower-leaf spring pair is mounted at one end by a clamping plate and two small machine screws
The flags are mounted on a special bolt which first passes through the sets front panel.  The flags are held under tension by two individual very light weight coil springs.  These springs can easily be missed if coated by a layer of dust or lubricant.

The Flags position is adjusted by small extensions on their bottom edges resting on their associated leaf spring.  In some cases these have warn or broken and have been replaced by small blobs of solder, wire or solder filled braid as in the photo above.  Adjustment can be fiddly.

With the dial unit missing, both flags should be visible through the associated viewing ports.  In the front panel views above only the grey flag shows as the red flag has been knocked out adjustment and requires re-setting.

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Adjustment and resetting of the flags can only be carried out in situ.  No specific procedure can be given as resetting them is a "fiddly" business at best and each repair/adjustment will likely require a different solution.   Study the illustrations on this page to gain an understanding of their operation before attempting resetting and take your time, ascertain what the problem is then devise a fix to get it right.  Working on these relatively fragile parts things can rapidly go "pear" shaped if rushed.
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Recommended lubricants.
  • Oildag for rotating shafts.  ( A fine oil loaded with graphite)
  • Inox MX6 for sliding surfaces.  ( A high temperature, high pressure premium machinery grease that will not melt)

 

PART ONE  Adjusting ZC1 Tuning Dial Mechanisms

PART TWO  Flick Tune Flags and Actuating Linkages.

PART THREE Refitting Dial Assembly to set.

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top                                                                                         September 2011