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

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PermO

Well-known member
Joined
Mar 16, 2011
Messages
792
Location
Hilversum, Netherlands
Yesterday I got a visit from a friend who is clearing his attic, he's an orchestral player and composer and once experimented with making electronic music the way it was done in the early days.

So, I got a ton of stuff and 3 boxes of old parts.

He told me to take it apart for parts as several "old guys who know tube stuff" have taken an attempt to make this work again without succes.
I don't think I can fix this, though I would love to see it working, also, there's some pretty lethal voltages going on in this thing, I don't feel comfortable working on this.

I don't have a variac, I have not powered it up, the story goes that it is "working" but it only shows a dot on the CRT.

But before doing anything to it I'd like to show what I've got and,... who knows...

DSCF3207.JPG
It's a tuning device... for instrument builders ?
I have not got a clue on how this thing operates, it came with a mic that is not functioning anymore but I was told it has once worked with a tonegen at the input.
DSCF3216.JPGDSCF3210.JPGDSCF3211.JPG

So yeah, I love the construction of this thing, and parting it out and use the frame for some tube mic pre build is defenitely an option for me.

So I wonder, what do you guys think ?
 
Hello

For sure look like a tuner.
Which probably compare incoming signal (from mic) with built in oscillator.
we can see 24 trimer which are probably variable capacitor coupled with mica caps, for precision oscilator tuning ?
front panel in french offer frequency tuning, sensibility (for the mic pre ?), a note selection as fixed or variable tuning.
Scope seem to offer brightness an focus of the trace.
The scope probably compare the two sources and offer kind of lissajous visual form ?

Regarding component useed it's a late 40' or 50' built
Beside the absolute pristin inside, for sure all those tar capacitor have to leave... as probably other part

I think if I have this in hand I'll try to resore it as is, and maybe mod it to output the oscilator and find a way to modulate it as sound generator, as to see how the inside mic pre can be used (without bulding other thing with the frame) !!
Right now I'm biased, I'm in the middle of a 50' french tube syth restoration (which share the same main trafo !?!)

Best
Zam

(in case...I can be interested :rolleyes: )
 
From what I understand the display shows a perfect circle when in tune, and a elips either tilted to the right or left when not in tune.

I rather not take it apart, I'd rather see it functioning again, if no one would have shown any interest in this thing it would probably be taken apart at some time by me.

I'm willing to part with it, as I don't have the skills to repair this, so I think you should have this.
 
If it shows a dot but no deflection with signal input, maybe it's an input stage problem?

In any event, that is super cool and if you want to sell, I'm willing to buy it.
 
Here is the same lookin trafo, this is the PSU/powerAmp unit of the Sythetizer I'm resoring.
Probably not the same secondary...
The brand is Vedovelli

Trafo.JPG


273472pubvedovelli.jpg

Best
Zam
 
From what I understand the display shows a perfect circle when in tune, and a elips either tilted to the right or left when not in tune.
I don't think so.
It shows a stable straight-ish line when in tune, and the line rotates when it's not in tune. If wildly out-of-tune, the image may vary from a straight line to a circle.
 
Hello

so it's not an XY lisajous ?
somthing like signal A -->X and Signal A minus signall B -->Y ?
Best
Zam
The most basic Lissajous has the reference going to X and the unknown signal going to Y.
Of course you may imagine any combination of these signals, and get different displays.
Indeed by feeding summ and difference signals you rotae the display by 45°.
 
Hi

The tube tuner is here
Very nice tool ! and the look is so "vintage"
I'll probably try to restore it as soon as I finish the current restoration (same area tube syth)
Then I'll see what mods (non destructive) can be done.
Like output for the mic pre and oscillator, or "keyboard" to play the oscillator :cool:

quick inspection show 2x 6AU6 , 5x 12AU7, and one 6BX4
seem like some lytic have been already changed, there is two nice rifa PEG124
I find the scope tube datasheet DG7/5 from miniwatt
https://frank.pocnet.net/sheets/084/d/DB7-5.pdf
Anode N°2 at 800V :rolleyes:

I'll have fun for sure :)

Thanks PermO (y)

Best
Zam
 
The trim capacitor array is crazy
Someone know what brand and technologies this is ? ceramic ?

EDIT: air spaced trimer piston capacitor, probably Philips

capacitor array.JPG
 
Last edited:
These are air capacitors. The electrodes are concentric. Capacitance is adjusted by controlling how deep one is plunged in the other.
yes, I find out in the mean time you reply
I unscrew one totally and as you say, concentric tubes that overlap more or less

Best
Zam
 
There is 24 of them and only one octave selection, the rotary switch have two deck, so probably there is two oscilators (for better precision ?), or the tube osc network need 2 trimer per notes, I'll se later wile drawing a schemo.
 
Hi

A very little update on this, I power it on yesterday for the first time (variac and A meter monitoring)
Move DMM prob around to look at some voltage. Nothing burn, all tubes glow, as the scope tube.

Get a circle for about a minute then fade to a dot as the tuner get warm.
Replaced lytic seem fine, but some TAR are suspect, with few having glass broken, need to change them all
There is 3 component type that I don't know what they are, I'll take pictures and ask for some guess later

I have other time consuming works on the go, but definitely will slowly try to make it work again...and be careful... I prob some 500+ on the upper (scope) side

Cheers
Zam
 
OK !!!

Seem it will be more easy than expected !
I'm able to have some figures on the screen :)
Basic suspect for now is ref oscillator instability and fade out.
Things being the ref oscillator stabilise more or less when probing (x10) around the circuit ?!?

So far topology is as follow:
-2x 6AU6 in cascade for the input stage, just a pot between the two stage for -sensibilité- , and second tube anode directly drive the scope grid.
-Ref oscillator consist of 3x 12AU7 tubes (5 triodes used), 3 triodes with cross couples anode to grid via dual capacitor network (the 2x12 trimer capacitors)... relatively complex...but I'll find out, and one tube I'm not sure yet what it dose in this network.
-Buffer stage with 2x 12AU7 which drive the 4 Oscope plates (X1, X2, Y1, Y2) from the oscillator circuit.
-finally the 6BX4 that rectify the B+

For what I just see, the tuner seem to work as a turning portion of a circle, CW too high CCW too low.
What seem damn cool is that at equal frequency the circle is half cut, at 1st octave the circle is 2 opposite quarter, at second octave you get 4 opposite 1/8 circle etc...and I think I catch a fifth that divide the circle in 3 portions !?!

Stand by for now, I'll make a BOM for all capacitors, and add them to my next order, hoping the unsustainable oscillator is due to leak at those old TAR capacitors. There is about two dozen to change, easy, just need to double check B+, especially around Oscop tube, usual 630V may be little short...

Cheers
Zam
 

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