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Re-Installing ZC1 Tuning Dial Assembly

by Chris Underwood ZL2CU

Refurbishing Tuning Dial    

A key part of of re-installing a ZC1 dial is ensuring that you do not cause damage to the dial assembly itself or associated parts such as the flick tune flag assemblies.

Set the two V notches on the flick set plates in line.  I usually set them behind the 3.5MHz graduation on the scale plate.

Check that the clamp is fitted as shown with the screw head to the right hand side with the slot pointing downwards.  Fitted the reverse way makes it very difficult, if not impossible, to access the screw head to tighten the clamp once fitted.

Note:  It is important that with the V notches set behind 3.5 MHz on the scale plate that the clamp is in the position shown.  If it isn't you will find the Scale plate is upside down when you attempt to fit the dial assembly.



Select "Flick" to allow the flick-tune followers to drop down and show at the top of the cutout in the front panel for the dial.  Lightly smear the followers with grease.

Next select "Tune" to to lift the followers up out of the way.  Carefully slide the the dial assembly onto the shaft of the variable capacitor.  Watch from above the set that the V notches of the set plates are centered under the followers.

The dial assembly should slide on about half way reasonably easily.  At this point resistance will be felt.  Select "Flick" to lift the fine tune drive wheel down allowing the scale plate to pass over it.  Sometimes it is necessary press the fine tune shaft down with your thumb while you push the dial assembly fully home.


With the dial assembly fully home, the scale plate should be flush with the dial indicator pin, check that the fine tune wheel is centered under the edge of the scale plate.

  1. Before tightening the clamp onto the tuning gang check the scale limit stops.  The small cheese head screw located near the large slot headed screw at the top of the dial cut out on the front panel is the main stop.  Cheese head rivets on the back of the scale plate limit the scales travel by striking the screw.  It is easy while focused on refitting the dial assembly to place one of these rivets on the wrong side of the cheese head screw making it impossible to set up the proper tuning range.

  2. Next check the Flick tune.
    • Set flick knob to tune.
    • Use the fine tune knob to set 4.5 MHz.
    • Use the tip of your finger to turn the setting plate nearest the front panel so that the V notch is under the front follower.
    • Lock the two grey set screws.
    • Use the fine tune knob to set 3.5 MHz.
    • Use the tip of your finger to turn the second setting plate so that the V notch is under the rear follower.
    • Lock the two Red set screws.
    • Use the fine tune to set 3.00MHz
    • Select Flick Tune and rotate the main knob anticlockwise.
      • First the tuning knob should lock at 3.5 MHz and the Red flag be displayed.

      • Continue rotating the knob and the the second lock point at 4.5 MHz should be found and a grey flag displayed.  (Blue if a Mk-2 set)

      • The locking points should be clean and decisive.  Reasonable, but not excessive, pressure should required to continue tuning for each lock point set.

      • Back off the the Grey/Blue set screws and a new lock frequency should be settable by rotating the main knob to the new frequency while flick tune is still selected and retightening the set screws.

      • Repeat using Red set screws.
    • Fully close the tuning gang and check the scale plate is set to the lowest frequency band edge.
    • Using fine tune slowly open the tuning gang until the head of the set screw in the clamp comes into view.  When the gang is about 170 degrees open the head of the set screw of the clamp should be fully accessible and can be tightened.
      • Caution:  Do not over tighten or you will break the clamp.  These die cast clamps are very brittle and break easily.  Finger tight is all that's necessary.
      • If you have ignored the earlier advise re fitting the clamp you will find that you cannot access the set screw head to tighten it, or that the edges of the clamp jamb on the flick tune levers preventing full tuning range being achieved.

      Your dial is now re-installed and should work smoothly and without slippage.

      • Note: The ZC1 Handbook warns that when fine tune is selected to use only the fine tune knob to tune the set.  Use of the main knob can/will form flat spots on the fine tune drive wheel and scale plate.  The main tuning knob is only for use with flick tuning.

    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)

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PART ONE  Adjusting ZC1 Tuning Dial Mechanisms

PART TWO Flick Tune Flags and Actuating Linkages.

PART THREE Refitting Dial Assembly to set.


top                                                                                         September 2011