[Hallicrafters] SX28 power transformer.

[Brian Goldsmith]

-----Original Message-----
From: Mike Everette 
Brian,

>What do your filament voltages look like?


*****Hello Mike and the list,,hope you are all well.

With 220V on the primary,the filament volts for the rectifier are OK at 5 as
too is the 6.3 V for the rest of the heaters/dial lamps.The rectifier plates
each have 400V (ie.,full secondary) (unloaded,I have yet to restore the rest
of the set).
What is puzzling is despite there being a 115/230V slide switch on top of
the transformer,there appears to be no connections to it nor does it alter
the primary in any way.Oh well,one of lifes little mysteries.Anothere
mystery is a 26V tap into one of the 400 V secondary windings,this is not
used in the 28.There is also another 12.6V winding centre tapped at 6.3,this
too is unused.


>The SX-28 power transformer is 580 volts full secondary, at something like
200 milliamps.  This should give, of course, about 290 volts or thereabouts
from the rectifier plates to ground.

>If you have an actual SX-28 transformer there, the secondary is waaaaay too
high and you might have a shorted turn in the primary someplace... but that
should also make the filament voltages look strange.

****It looks like I have a non 28 transformer here given the HT secondary is
so much higher than original.

>Have you checked the current draw for the primary?  Wonder if you might
have 230 volts poured into something set for 115....?

**** Yes,I have,primary runs quite cool although the HT is not yet drawing
current.

Halli used a number of transformers that looked alike, i.e. used the same
case style as the one for the SX-28 (square top).  The SX-88 and SX-101 are
two receivers; I think one or more of the transmitters had similar looking
iron -- switch and all.  But no receiver would have used a transformer with
over 600 volts on the full secondary if memory serves me.

*****That is almost certainly what has happened here,you have helped
greatly.
Many thanks,Brian G.