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Meat Plow[_5_] Meat Plow[_5_] is offline
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Default Boss TU-120 Electronic Tuner Schematic Roland LED Strobe GuitarTuning

On Fri, 04 Mar 2011 00:04:30 -0500, Wild_Bill wrote:

I have an older Boss TU120 tuner (maybe 1979) that seems to need
adjustment repaired, but have been unable to locate a schematic or
service manual.

The output frequency at the Monitor jack, appears to be incorrect for
the internal Calibrate settings, and when checked with a reliable
counter (SC3100 AutoTracker readout) the freq is about 432Hz, when I
think it should be adjustable to over 440Hz.

I was about to ask Roland Support when I saw that they require
registered user identity sign-in/account to be established before asking
a question.

I have the operating instructions, and it describes the pot adjustment
for the internal Calibrate steps, as something like "adjust the front
panel Cal (pot) until the drifting stops, and the LEDs appear to be
stopped/remain stationary".

The point of rotation where the front panel Cal pot gets the LEDs to
stop drifting is all the way to the end stop of the rotation, so I can't
find the mid position between scroll left/scroll right.. and the freq is
about 432Hz, not 440, when I assume that it should be able to adjust
from below 440 to over 440Hz as the Calibrate pot is adjusted.

The Calibrate output freq is independent of the 12-position Note
Selector switch.

I marked the 2 internal PC mount pots before twiddling them, but the
freq doesn't get to 440Hz.
After tweaking, I can see 129Hz For "C", not 130.81..(possibly just a
counter accuracy tolerance issue) but 242Hz for "B", not 246.9Hz.

I believe the tuning reference freq is from a 3-terminal component
marked Iwata 880.0 T (3 '79 Japan) with a tuning fork symbol on it.

I'm operating at a musically impaired level here, as I've only recently
become interested in learning to play guitar, and I don't fully
comprehend a lot of how actual frequencies relate to notes, other than
the harmonics.

I have a functionig Boss TU-12 Chromatic tuner, so I don't really need
the older tuner, but I'd like to know if I can get it to work properly,
since it does have a strobing display that easier to see at a distance,
moreso than the-needs-to-be-positioned-closely TU-12's meter pointer.

I'd also like to lower the non-adjustable speaker volume too, perhaps
later.

I don't think installing a 0-6 volume knob would be a solution.


http://guitartunerguide.com/

If you need brushing up on the theory. Closest I have is a TU-15. If it's
layout is similar I could give you some freq readings for reference.


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