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Be sure all hardware at these points is secure. ------------------------------------------------------------------------ Thats everything I show up to 1989 that covers the HD-10 Keyer. Enjoy! ------------------------------------------------------------------------

July 31, 1989

HD-1234

Bulletin No:

Coaxial Switch

HD-1234-1

Knurled Nut Change

The knurled thumb nut on the ground post on the HD-1234 is changed to a readily available type as follows:

Thumb Nut from [PN 252-23] nut to a [PN 252-824] nut.

Mark this change in your shop manual for future reference. ------------------------------------------------------------------------ Thats everything I show up to 1989 that covers the HD-1234. Enjoy! ------------------------------------------------------------------------

October 10, 1977

HD-1250 Solid State Dip Meter

Bulletin No: HD-1250-1

Calibration of Oscillator Circuit & Check-Out of Detector Circuit Operation

1.

2.

Build p

[SM-110

C].

lineari

ty.

Adjust

scale so hair-line aligns properly with low end of scale.

Calibrate HD-1250 oscillator with C21C and check

3. Connect this ci of at l Mhz coi action -----------

the pick-up coil and 150 ohm resistor in series and place rcuit across the output of a signal generator that is capable east 10 Mhz. Adjut generator at 0 db/9 Mhz. Insert 6.3-13 l into pick-up coil. Adjust dial to 9 Mhz to verify dipping of meter. -------------------------------------------------------------

February 27, 1981

HD-1250 Solid State Dip Meter

Bulletin No: HD-1250-2

Low or No Meter Indication With Brown Coil Installed

Check the length of the leads of Q11; Q11 should be approximately 1/8" above the oscillator board.

Check for 1/8" spacing between the oscillator board and turning capacitor, C21; this spacing is critical. If necessary, remove oscillator board and remount to obtain the 1/8" spacing. ------------------------------------------------------------------------

July 30, 1982

HD-1250 Solid State Dip Meter

Bulletin No: HD-1250-3

Will Not Oscillate at High Frequency

This is caused be a National brand transistor installed at Q11 on the oscillator circuit board. To correct this problem, replace the National transistor with a Motorola brand [PN 417-290].

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