[TinCanAlley]

Originally Posted by zeno

Most Zenith transistors are marked with a partial number.
Most start with 121- but usually thats left off.
Example is the hoz out. Its a 121-831 but only the -831 is
on the part. Later subs may have a different number. IIRC it was 121-1029
and was subbed to a 921-500.

Your color outs I would decipher:
743 = 121-743
F314 = maybe Fairchild & there EIA code or the date code.
Dont know what the 16 is.
Remember those color outs were used from IIRC A line through
CC2 sets & probably had a host of part ##'s but as long as you
up sub they all should work.

Anyhows later on they may use a better transistor that also
works on the old sets that used the 121-743. The old number
gets sold off & when gone the new number takes over 100%.
THIS IS NOTED IN THE Z PARTS CATALOGUE !!!

What is needed is a Zenith parts catalogue. But I have been looking
for one for years. They were VERY common, any Tom Dick or Harry
could get them from any Zenith parts distributor.
For now use the SK, ECG, TCG etc sub books to see if things up sub
& make sense.

73 Zeno
LFOD !

I figured out a ways back how to figure out part numbers on some, but not all. With what I updated, I used the SM to determine part number, then realized the paper on the inside of the cabinet had them for some important parts and modules. It was after that I realized the part numbers differed on many from what was called for and what was installed. With some help from Talon Electronics, I was told that the numbers on the paper and newer and supersede those installed. So that has always confused me. If they had newer parts (according to the paper in the cabinet), then why did they populate the set with so many older parts? Why not put in the older paper with the older part numbers. Crazy.

It was one reason I didn't change the 24V regulator as I couldn't verify if the part installed could be replaced with the one on the paper. Since I didn't seem to have a voltage issue, I just cleaned it up and installed a new insulator under it.