Thanks Nigel.. I believe that you're correct, and that even oxidation of a
mechanical tuning fork-type device would likely upset it's characteristics..
detune it.

I didn't think to feel the 880Hz component to see if it was actually
vibrating while I had it apart, but maybe it does.

The 3-terminal gizmo is maybe 8x12mm with maybe a 10mm height (metric, how's
that? heh). The thing is marked Iwata Japan, and a symbol (((Y))) except the
Y looks like a tuning fork.. I just assumed it was a ceramic resonator or
something similar.
If it hadn't been marked 880, I wouldn't have thought it had any direct
relation to the 440Hz that is supposed to be the Cal pitch/note? frequency.

The front panel pot (far right end of front) for the user to set during the
Cal setup is about as physically far from the 880 gizmo as it can get.

http://www.bossarea.com/other/tu120.asp

My days of drawing even partial schematics are essentially over.. I used to
do that stuff when I was driven by ambition and inspired by satisfying
curiousity.. but anymore, it just eats up countless hours, so I generally
avoid it.

I checked the values of a few items near the I/O jacks in case they'd been
subjected to a misplaced voltage source or similar mistake/external
equipment fault, but that was the extent of actual checking anything other
than reading the output freq.

I recall that the 880 gizmo was at one end (by the rotary selector) and the
right end appeared to be a combination of I/O jacks, audio circuit for the
speaker (faces up thru the top grille) and an area of ICs which seem tied to
the circuit that operates the strobing LEDs (which don't actually strobe,
but light in sequential groups of 2-3 which will appear to drift left or
right, but stop drifting when the note is accurate).

BTW, there is a front panel mic (beside the front pot) for picking up
various instrument sounds, or an electronic signal can be input into the
unit (electric guitar cable, etc).

I suspect that the 30+ year old components' values have drifted, and a
schematic or service manual would be the most practical approach for me.

As I mentioned, I have a tuner that works, but the older TU-120 appears as
though it would be handy to use.

--
Cheers,
WB
..............


"N_Cook" wrote in message
...
If the 880.0 contains a miniature tuning fork, like those watches of the
early 70s that hummed to themselves. Corrossion to the forks over decades
would lower the frequency