Accordeur Électronique B.L.N type T.V.M

[zamproject]

 

[PermO]

You got it going ! that's so cool !

 

[zamproject]

Yes, with tone generator, don't try yet with the fitted microphone, it need a new wire as one end is missing special connector.
I'll fix all details later with all capacitors change, HT for scope is at 520V
Also need a safety ground, and probably a time consuming calibration (24 variable capacitors) as all frequency are little low by 3 or 4 Hz in fixed mode.

This is a cool piece of gear

Thanks @PermO !!!

 

[zamproject]

So after little in depth on the topology, and to refine my post #20, so far the principle is as follow:

Input to be tuned is sent to the scope grid, so the beam is directly modulated by the signal.
Ref oscillator which is more or less an astable multi-vibrator is taken from 4 output, each 90°, to drive the 4 X/Y deviation plates thus drawing a circle at 1 turn per ref frequency.
That's why we can see harmonics by circle division, like a 5th pulsing the beam 3 time wile the circle (ref) is pulsing 1.

Perfect correlation make the rotation stop

This is so cool because you can compare and weight the natural harmonic of a chord or a pipe with a -mechanical- division of it. So this make sense for instrument builder (as PermO picture in post #13) to fine tune an instrument.

Visually it's very nice, I don't think I get any synaesthesia...but without sound and just by looking at the scope my brain feel the intermodulation pulses when you get close to correlation...
Never get this sensation with any other type of tuner

Cheers
Zam