RadioBanter - View Single Post - Harvey Wells T-90 question

Scott Dorsey · October 1st 06, 09:31 PM posted to rec.radio.amateur.boatanchors

wrote:
Joe,I have a H/W T-90 The mod driver shows 400 Ohms one side and 390
other side. On these older rigs it is not uncommon to find un-balance
in the windings and many have had the driver xfmr replaced,,windings
are extremely small. gauge wire..I know the people that built them
never expected us to be using them over 50 years later...hi..A great

The resistive measurements will not be the same because one half of
the winding is closer to the core and therefore has a shorter length
per turn. So that may have perfect AC balance, even though the DC
resistances don't match. The DC resistance is proportional to the length
of the winding, which is not directly proportional to the turn ratio.
In the case of the rig with the 390/400 resistances, it's probably balanced
better than you think.

But the origininal poster's rig... that 200 ohm number doesn't sound good
to me. Put 6VAC 60 Hz into the primary and measure the ratios... if there
is a shorted turn, the DC measurements may change a little or a lot, but
the AC measurements will be totally off. On the other hand, you may have
a different transformer than was original; if so the DC measurements will
be completely off but the AC numbers will be fine.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."