[AMRadio] Halli HT37 Phasing Mod problem


Geoff/W5OMR ars.w5omr at gmail.com
Tue Nov 27 18:05:57 EST 2007


DOXEMF at aol.com wrote:
> Geoff,
> I seem to be getting very good carrier null but then the sidebands are not correctly spaced in frq.
>   When in AM DSB mode the modulation is not symetrical and has af response issues. Everything aligns good up to the RF phase ballance adjustments where the variable C phase trimmer works but the Variable L trimmer has no effect. 
>   Looking at the related 12AT7s with socket extenders shows
> no change in the L side tube no matter how the trimmer is adjusted.  I may not have these trimmers at the proper range
> but it's difficult to tell just what that is from the manual.
>
>   It's near impossible right now for me to remove the box again and do component testing with major Rheumatoid Arthritus
> issues.
>   

You might have to get a neighborhood kid over, Bill, to help you with 
that.  What it sounds like to me is, that the little coil has a broken 
wire either in the windings around the form, or at, or near the legs, if 
adjusting the coil makes no difference in audio phase.

Break out the magnifying glass!

Speaking of which, sometimes Harbor Freight (if you have one of those 
near-by) has a clamp-on, lit, magnifying glass for such delicate 
projects.  Last time I saw one there, it was reasonably priced at around 
$20.oo (19.95+tax).

Good luck!

-- 
Driving your AM Rig without a scope, 
is like driving your car at night, without headlights. (K4KYV)

--
73 = Best Regards,
-Geoff/W5OMR



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