Re: Tektronix 575 122C trimmer capacitors


Yeah, reckon so.

The plot has thickened a little bit as I've searched even more documentation on this pesky little trimmer capacitor.

Here's the latest: Specifically, in the 1964 published version of the field version of the Mod122C, the mysterious C239 capacitor is specifically mentioned. In fact, the part is specifically INCLUDED in the field kit for Mod122C. Even more, there is a specific instruction about how and where to add the part, including a drawing of where it goes!

See for yourself:

pdf pages 5, 16, 17, 21 manifest, mentions, drawings, cal procedure for the use of the part.

This seems to mean at least one thing with a fair degree of certainty. On Scopes built before 1964 and not already Mod122C, Tek was expecting at least some of the field modified 575 to be missing this part. Thus, the kit made provision to add the part. That's why it is part of the kit as issued in 1964. Remember, by 1964 the 575 was well past the "#101-4779" notation.

Bottom line: In 1964, Tek thought C239 should be there on 122ModC versions.


a.) C239 - it appears it was NOT present on some (or all?) 575 versions built before 1964.
b.) It appears that by 1964 Tek specifically ADDED it for 122ModC field modifications on such scopes.
c.) One can only presume that, in Tek's opinion, it is a necessary part for 575 122ModC, (or at least the field version of the mod)

So then why is it MISSING from my circa 1962 575 Mod122C curve tracer?

The only conclusion I can draw is that it was an improvement made after 1962 and not a deletion. Otherwise, I can't come up with a reasonable way to explain why on my '62 model, and on others I see posted on TekWiki, it is absent. But in 1964 field modification kits, C239 was clearly specified and supplied.

Great! now I'm torn...
Maybe I'll just put one in and see if it creates a time-vortex or black hole or something. :-)


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