[AMRadio] GK500 OTA almost

Donald Chester k4kyv at charter.net
Thu Jan 5 15:32:34 EST 2017

> A lot of them made little changes in mid-production without changing
> the schematics or parts lists.   If you run out of 200 ohm resistors
> and have to keep the assembly line going you raid the 400 ohms and
> two and keep moving but a manual re-print for that?  Too costly.

One of the worst offenders for this was the UTC transformer company.  They
sometimes made drastic changes in the essential characteristics of some of
their transformers without making any change in the type number, not even
adding an "-A" suffix.  One example is a power transformer that had plate,
rectifier filament, bias, and tube filament windings.  The filament winding
on the original was 2.5 volts.  Later editions of that same transformer,
with no alteration of the type number, were identical to the original except
that the filament winding was changed to 6.3 volts.  An unwary customer
might have purchased a  newer version of the transformer to replace a
burnt-out original, and unknowingly zap all the 2.5 volt tubes with 6.3
volts, until the 6.3 volt winding gave up the ghost because all the 2.5 volt
tubes wired in parallel put a near dead-short load on it.

Another example was a broadcast-grade class B driver transformer, in which
they drastically altered the step-down turns ratio without changing the
transformer's type  number.

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