[Collins] ID a bunch of Collins power transformers?

[Dr. Gerald N. Johnson]

On Tue, 2006-02-21 at 06:40 -0800, Ian Wilson wrote:
> Hello, new member here.
> 
> Is there a resource out there that would help with this? Looking to identify
> about 40 transformers, mostly 672- and 674- part numbers.
> 
> Thank you.
> 
> --ian, K3IMW
> 
Way long ago when I worked at Collins their specification books were
handy for that. Today all we have are the various manuals for equipment
that list their transformers. There were many that weren't commonly
used. One can look for a vendor part number, sometimes standard vendor
parts were relabeled for Collins use. Sometimes an open catalog part had
a metal cover added and the original catalog number is still on the
paper over the windings. But often the transformers were custom made to
fit Collins specifications even if the main part of the custom
specification was paint color and part number mark which makes them hard
to identify. Generally Collins parts used standard wire codes so that
voltages can be identified by the ball park values from those codes
(brown being 5 volt filament, black being primary, green being 6.3 volt
heater, red being high voltage) and currents for low voltage by wire
size, the total power capability by core size or transformer weight.

To add complication, not all transformers were made for power, some were
for audio, some for power at aircraft frequencies, some for servo motors
at odd frequencies.

It should be possible for power transformers to identify current ratings
by comparing winding resistances to standard catalog transformers (helps
to have catalogs from the 50s and 60s with complete details) and to
consider wire size choices in designing those transformers. One could
apply a load and measure the voltage drop from the winding, then run
that load a while and measure the temperature rise of the winding
resistance and from that assign a reasonable winding rating. The
difficulty is that then one also has to presume a value for the
conservatism of the design. A transformer designed for consumer and
intermittent use can run twice the current density (accompanied by a
more rapid temperature rise) as a transformer designed for conservative,
cool, and long time operation. And the allowed temperature rise depends
on the survival temperature of the wire and layer insulation plus the
varnish used in the transformer. A transformer in a weight critical
application like a space craft may not be designed for cool operation
because each ounce of weight takes pounds of propellant to reach orbit.
That is to say, there are many variables in the design and application
of a transformer that aren't always instantly apparent when trying to
work out the recycled use of that transformer.

That being said, start by listing your transformer numbers, some of us on
this list may recognize them. And some I've picked up had schematics and
full ratings silkscreened right on the transformer case. But still didn't
identify the original application. Having the specifications book may or
may not identify the original application. Collins wasn't consistent about
identifying applications of components because once in the specifications 
it was cost effective to search the specifications for a component (indeed
there was a notebook of preferred specifications) for a new project saving
the cost of specification preparation and vendor/component qualification 
to that specification. So a component could have been used for several 
applications and a particular application could have used several part
numbers over its production runs as vendors came and went. Sometimes a
part changed part number when it change vendor because the near standard
part of the new vendor wasn't quite the same size or current ratings, but
was close enough to work.

-- 
73, Jerry, K0CQ, Technical Advisor to the CRA
All content copyright Dr. Gerald N. Johnson, electrical engineer