GREAT “SCOTT”…y !:


In pulling the ZENITH factory referencing for your sets’ 5H01 chassis, reveals it to be using the larger profile IF transformer, and not the usually
expected “K-tran” style of ¾ inch cased unit that most were expecting.

That unit exhibits a complete different mechanics in its built in mica capacitors for the two I.F. coils. Its reliability, mainly dependent upon the
pressure contacts in interfacing to the silvering of the mica disc.

Therein, you have two dissimilar metals and the high susceptibility of that silvering taking on a black Ag0² coating, along with the yet later
possibility of that oxide then taking on a progressive buildup and lateral migration.


That is particularly the case, if the surrounding air is laden with high humidity and the presence of airborne sulfurous and nitric oxides mixed in.


If I see that series of transformers, usually I can whack the case a bit and the unit will respond with a static burst or slight tuning shift, and the temp
weakening of reception if it is tuned into a weaker station.

Doing a full disassembly of the unit will permit me to inspect the mica dielectric disc and the companion “petals” of the contacts
that mate onto the disc.
A dipping of the disc into a liquid jewelry cleaner and brushing action gets rid of the black oxide and a white vinyl eraser removes any balance being left.
Then one checks the peripheral edge if the mica disc to see if an Exacto blade is needed to scrape / remove any silvering that might be interconnecting
or permit arcing between adjunct segments and front to back segments on either sides of the mica disc.

A final procedure is to use the eraser to clean the contact areas of the “petals” and the mating portions of the silvering on the disc and then a degreasing
to remove any possibility of eraser contaminants.

Then there was reassembly and a touch up of the 455 alignment of the set.

In some few cases where the mica disc was not reusable. . . . one time I used drafting film. . . .on another, I used the clear plastic. . . . (one sees it being
used in the clamshell containers for veggies, fruits, foodstuffs). . . . . in order to make a disc to insulate / separate the contacts and along with its inherent
dielectric capacitance that it would be presenting.

With the I.F. tran then reassembled, I had adjustable capacitors tacked in externally across the pri / sec coil windings and previously had centered the
slugs within the coils while apart and then moved the slugs outwardly ≈ 1/2 of a slug width.

The 455 alignment was done with the variable trimmer caps and then they were pulled and measured so that fixed silver micas of those values could be
installed externally .

I have photos of the infrastructure of that particular series of Zeenuts I.F. transformers and will initially post just the different blowups of its construction
and then should be able to add in the textual particulars in a day or so.


See, the separate . . . . . Anatomy of a Zenith I.F. Transformer

Tech Info: