Conn Strobe Tuner

some guitar techs still like this tuner,

kind of a classic circuit, like a GenRad inductance bridge, ahead of its time, so still usable after time passes it buy,

looks like somebody left a can of Starkist Tuna inside here,  probably a roadie for the Allman Bros or somebody,

labor intensive construction, kind of like a Blaupunkt car stereo, ever seen the indise of one of those? sheesh. 

wow, lots of diodes, probably some type of step comparator,

or not,

power switches lead a tough life, mechanical and electrical stress, over and over again,

this sw is mounted on a wafer switch, don't wanna hassle getting a new one and spending all day wiring it up,

so we just jumper the sw and put it on a power strip, case dismissed....

Wow, I have one of these.  Whenever I need to set guitar harmonics, I use the Conn for the precise locations.  It's easy to see on the strobe  light.  Much quicker than my roland tuner.   

That's beautiful! I want one to sit on my desk so people ask!

JS

cool info on the Conn stuff hear>

http://www.mts.net/~smythe/st-11.htm

Forum here>

http://www.petersontuners.com/iforum/lofiversion/index.php?f9.html

hard to read schemo>

> hard to read schemo

There's a less-grey but still JPEGed version in one of your links.

Top-left must be a master oscillator.

By the connections to the C...B 12-way switch, the dividers and diode matrix must form a top-octave generator (never seen this type).

Top-right is a very funky power amplifier and 2-phase motor for the rotor (tuna can).

Signal In is in the middle and gets a basic 3-transistor amplifier.

Bottom right are the Neons, and their amplifier, which I guess can be switched to the boosted Sig In.

I think the extra junk to the right of the Sig In booster is an octave divider for the "+2" function. The highest notes use the narrowest stripes and they are just hard to read. "+2" transposes the notes in bands 7 8 to band 5 6, where the stripes are wider.

Bottom center is a thing called a "transformer", which is too tricky and complicated for present company.

There may be a tap off this mysterious "transformer" which feeds 60/120Hz to the neons for calibration. (Do you trust your local Hydro to be more accurate than your conductor's pitch-pipe? Maybe today. Long ago line frequency wandered hour to hour, they just got the right Cycles Per Day so electric clocks didn't drift.)

Bought mine in 1981. Still in use. Should I recap anything?

here is a cool thread on this box,



http://www.diyaudio.com/forums/instruments-amps/135711-conn-st-11-strobotuner-mod-help-2.html