[AMRadio] Suggestions for restoring a DX-100

wwd at netheaven.com wwd at netheaven.com
Thu Apr 4 11:40:41 EST 2002

>Remember, a lot of older equipment was designed when "full gas" was 110 
>volts.  For some reason, the ac power in most areas has now been boosted
>up  to about 125 volts, which will shorten the life of the components.

>I have thought of rigging up a variac with a rotary switch, so that it 
>functions like the old fashioned on-off/volume control they used to put
>on  radios.  To turn on the rig, rotate the variac clockwise, and the
>switch  snaps on.  Then manually run the variac slowly up to max (or to
>the desired  voltage).  To turn off, rotate the variac anti-clockwise
>until the switch  snaps off.  This would gently turn the rig on and off
>with every use and  undoubtedly extend the life of many of the

>Don K4KYV

Or using a filament transformer to buck down by several volts. An old HP
scope transformer with several separate filament windings serves
buck/isolation duty here quite handily. The rotary switch came from the
scope, too. You can start @ 84vac, 95, 110, and finally 120vac.  Since
there are 2 independent primaries they can be wired to provide full
isolation from the powerline, but this reduces the load capacity. Still it
hardy ever gets warm. Bill K2AME

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