[Hallicrafters] HA 1 Keyer

[Roy Morgan]

At 11:11 PM 7/10/2005, Rinkie & Ron Pollack wrote:
>Any experts out there on this item?
>
>I can't get the weight and balance to work.  The dots are too short (when
>measured on an ohmmeter, cannot get half scale.)

Check all the resistors in the multivibrator.
Replace any that have drifted more than a little bit.  Especially R1, R2, 
R6, R7. 2.2 and 5.6 meg resistors..

Those resistors aroung V3 may also be giving trouble. 470K, 1Meg, 
100K.  R25 is a 2.2 meg and should be checked.

Replace all paper caps in the thing.  Do not fool yourself into hoping they 
are still ok.  C1,2,3, and 9 are "molded tubular' caps and they are the 
suspect ones.  The disk ceramics are unlikely to give trouble (but might). 
Any tubular paper ones almost certainly are causing trouble.

>Did the balance procedure
>per manual.  It works, but the space between constant on and where the dash
>starts is only about 20 degrees of rotation.  I seem to remember a bigger
>gap.  I replaced V3, and substituted for the other tubes, with no change.



>
>Only discrepancy is that the balance pot, 500K, measures only 300K.  I don't
>remember ever having a pot change so much!

Measure it out of the circuit first.

>  I'll replace it, but need to be
>sure that it's a linear taper, and what wattage is appropriate.

Likely any pot will work fine.  I would expect a linear taper, but use what 
you have.

Roy

- Roy Morgan, K1LKY since 1959 - Keep 'em Glowing!
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