110vac ver 120vac

[Jerry-n5ugw]

I'm concerned with running a transformer designed for 110vac on 120vac. I've read it caused a lot of heating in the transformer.
Q1) is this a problem in DX-100B's and what design of bucking transformer is used to buck the 120v to 110v @10A? Thanks

[Pete, WA2CWA]

The DX-100B manual specification sheet indicates AC input as 115 volts AC. My Apache, Viking II, Ranger,  and numerous other boat anchors, have tolerated 120 plus AC volts for many many years.

[Jim, W5JO]

Most if not all old radio manufacturers specified 115 VAC 60 Cy input voltage.  They also knew the electric company's tolerance was 10%.  So to have at least 110 volts at the end of a rural run, they would install capacitor banks along those long runs.  People living near those banks would see 125 volts at their outlet.

So 115 X 10% = 11.5 + 110 =121.5   or   115-11.5 +103.5.

125 is not that far from 121 and I, like Pete have never had trouble provided the filter chokes and capacitors met specs on leakage.  Now your filament voltage may be a bit higher but you won't see that much difference in tube life.

[WA1GFZ]

The low voltage transformer in my V2 CDC ran pretty hot. The last round of changes I solid stated the power supplies. The two 5 volt windings were not needed after the change. My real concern was the heater voltage ranging between 6.7 and 6.8. I ended up putting both 5 volt windings on the neutral side of the 110VAC line. (A three wire line cord was also added)This dropped the heater winding to 6.2 to 6.3 volts.
Also the temperature of the transformer dropped a lot. My line is usually close to 126 volts so the 110 volt winding must have hauled a lot of current doing nothing. I think it was close to saturation at that high line voltage.
I ripped out the useless TVI line filters and installed a terminal strip in its place to make the connections.