[Boatanchors] NC-173 transformer question(s)

[Nick England]

I haven't had an NC-173 or 183 in some years so can't remember if it was a
common thing because the xfmr was under-rated and overstressed by poor
design - but probably not.

Is it still actively oozing? or maybe this is something that happened a few
years ago and the tar has been there for a long time? Seems highly unlikely
that a xfmr would be oozing tar just from old age - something was probably
wrong and it was overheating.

Transformer overheating would have been the result of the rcvr drawing too
much current - maybe a bad filter cap or rectifier tube. Maybe a bad tube or
bad coupling cap causing the audio output stage to draw too much current. (I
mention the audio output stage because it was driven directly by the power
supply - other stages would have had a resistor in series and that would
limit the current). Much less likely, but possible, is a shorted winding in
the xfmr. But I think all these would show up as low supply voltage
readings. As I said, maybe this happened some time ago and the bad tube or
cap got replaced.

If you can put your hand on the xfmr after an hour and it seems warm or
pretty warm, but not so hot you say "ouch", then I'd say don't worry about
it.

But you can always start asking on the lists if someone has a spare xfmr
from a parts rig, or find out the specs and see if another xfmr will do -
for a rcvr like the NC-173, the xfmr is most likely nothing special and you
can find a replacement pretty easily - certainly no need to spend big bucks
on rewinding. For example, I sold two NC-300 parts units for $25 each at a
recent hamfest and they both had good xfmrs.

good luck,
Nick KD4CPL


-----Original Message-----
From: boatanchors-bounces at mailman.qth.net
[mailto:boatanchors-bounces at mailman.qth.net] On Behalf Of WØQFC
Sent: Wednesday, February 20, 2008 9:39 AM
To: National at mailman.qth.net; FLBOATANCHORS at yahoogroups.com;
boatanchors at mailman.qth.net
Subject: [Boatanchors] NC-173 transformer question(s)

Again, I want to ask the collective opinion of the various list members 
about my 'problem':

The power tranny is oozing black tar.

There is some on top around the mounting flanges and some under the chassis 
that has dripped on parts and wires.

The voltages are correct and the receiver operates ok. There is a normal 
temp rise after it has been on for one hour (+).

The BIG questions:

Is this a indication of impending failure or is it normal for a part that is

this old (62 years)?

Would it work to remove the tranny and some way seal it with epoxy or 
something else?

If this tranny is failing then it brings up the question of is it worth it 
to even restore this receiver, especially when you consider a re-wind cost 
of $100+. . . .

I will appreciate your collective opinion and

TIA






73

Gene, WØQFC

www.w0qfc.com

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