[sdiy] Tiracon 6V - Vermona / VEB Cottbus - Help and Schematics Needed

Mon Nov 8 18:33:20 CET 2010

Heyho!

Look around for a Book called "Moderne Musikelekronik" from Hans-Jochen
Schulze an Georg Engel. (Militaerbuchverlag der DDR, Berlin 1989, ISBN
3-327-00772-1).

There are the Schematics for the VCO/VCF/VCA Part and some other useful
information. I have the book here and could propably scan some pages, if
you need them quick.

The IA317/AK317 is a GDR-Clone of the LM13500.

The VCO is a Saw-Core type, where the first 4066 is used as Reset-switch
using all 4 channels in parallel (for lower R?). The -12V Rail goes to
the tuning trimpot (100k between +12V and -12V).

cu, Markus

Am 08.11.2010 15:21, schrieb cheater cheater:
> Hi guys,
> 
> I am trying to resurrect this Tiracon 6V that I got off eBay some time
> ago. It doesn't put out any sound.
> 
> It came to me in a non-functioning state. Since then I have repaired
> the PSU (hopefully correctly) and have been trying to work out why it
> doesn't work, and how it works in the first place.
> 
> I have tried contacting Vermona about the synthesizer, however have
> had no luck with getting a reply about schematics etc.
> 
> Currently, the digital board with the LCD turns on, and I can load and
> edit patches (haven't tried to save them yet, not sure if that's such
> a good idea). I can also change the speed of LFOs which is depicted on
> the LEDs pulsating quicker or slower. There is no sound coming out of
> the synthesizer.
> 
> It does seem that the scanning matrix works to some extent, since the
> voices do seem to get triggered.
> 
> About the synthesizer layout: if you look at the pictures here:
> 
> http://www.vermona.de/htm/tiracon2.htm
> 
> then you'll see the arrangement of the boards is as follows:
> the top of the synthesizer opens and has the LCD board in it. When
> that's open, we are presented with several boards. From left to right:
> 
> 1. leftmost: digital board - http://www.vermona.de/Tiracon/digitalteil.jpg
> 2. main/analog board with six voice cards -
> http://www.vermona.de/Tiracon/analogteil.jpg
> 3. regulator board
> 4. rightmost: transformer board
> 
> (both PSU boards can be seen here: http://www.vermona.de/Tiracon/netzteil.jpg )
> 
> The voice cards themselves have a 2mm pin interface of some sort that
> they plug into. I have been trying to scope them out.
> 
> About the PSU repair: the top left regulator (B3170V, an LM317 clone
> from the GDR) was not in circuit and one of the capacitors has broken
> loose. After soldering it all back together, I have had +15V show up
> on one of the pins, where it was 0V before.
> 
> About the voice cards:
> Pictures can be seen here:
> http://www.vermona.de/instrumente/tir3.jpg
> http://www.vermona.de/Tiracon/6-voices.jpg
> 
> they have two connectors, call them the Left and Right connector. The
> Left connector has 12 pins, the Right connector has 6 pins plus a "key
> pin" which doesn't do anything.
> 
> Here are my notes for the connectors:
> Left:
> 1. frequency CV, V/Hz
> 2. 15V
> 3. GND
> 4. -15V
> 5. ?
> 6. 3.69V with a lot of digital noise
> 7. digital gnd?
> 8. digital gnd again?
> 9. ?
> 10. 5.2V
> 11. unused
> 12. -12V with a lot of noise
> 
> Right:
> 1. ?
> 2. very very quiet white noise. Perhaps the output pin?
> 3. ?
> 4. white noise, probably an input from central distribution.
> 5. gate. off = -7.29V, on= -7.53V
> 6. -13.23V
> 
> About the Left connector signals:
> The Frequency CV is very weird. C3 is -0,470V, whereas C2 is -0.233V
> and C4 is -0.945V. Obviously has a scaling problem, which I hadn't
> tried to address yet, since that's like waxing a train wreck. The
> weird thing is that the voltages are all negative.
> 
> Pin 6 in reference to pin 7 still has the digital noise, but the
> amplitude is reduced by 50%. Pin 5 seems to contain a very very quiet
> mix of the output, I might be wrong though. Or maybe it's just some
> current escaping through ground to somewhere, who knows.
> 
> 
> About the cards:
> 
> I have been able to get the 6V to run to some extent: the voice boards
> receive triggers and they change in pitch according to the note being
> played. The oscillator is audibly changing pitch if you listen to it
> by tapping the voltage on either of its terminals directly (which is
> funny, because I had thought only one of the terminals would have
> output, but both do - one of them is much quieter though). I have had
> a look around the board as to what it has got and it basically has two
> areas. On the left there is the VCO and on the right there is the
> filter.
> 
> One weird thing is that there is a droop in the oscillator's pitch as
> long as the key is being held down. That means, that I will press the
> key (repeatedly until the voice I'm scoping gets triggered), and the
> pitch will change to what it should be minus a few semitones. Then
> when I let go of the key the pitch jumps up.
> 
> The Gate is VERY weird. you can see the voltages above - off is
> -7.29V, on is -7.53V. Definitely something wrong going on there.
> 
> The VCO area contains resistors, some small capacitors, some other
> stuff which I am unable to identify, and these chips:
> V 4 082 (probably a TL082 clone)
> B084D V7 (probably a TL084 clone)
> V 4066 D (a CD4066 clone, a quad bilateral switch)
> a second 4066
> CD4013 BE (probably the only western chip in the whole voice board).
> 
> The presence of two quad bilateral switches and the fact that the VCO
> wave is audible on both ends of the capacitor (which is 15nF) suggests
> to me that it is a triangular core vco. I assume that the second
> switch is used for creating a sawtooth wave. I'm assuming the CD4013
> is used as the comparator in the reset circuit (it is a CMOS dual
> D-type flip flop).
> 
> The filter board is about the right 45% width of the board, and it
> contains four chips marked as IA317D UD, some resistors, and some
> small foil capacitors as well as tantalums. The chips appear to be
> also known as AK317DC. Here's a thread about it in Polish:
> 
> http://www.elektroda.pl/rtvforum/topic755331.html
> 
> (google translate might help)
> 
> For example it was used in some old laser printers to control motors.
> In the thread it is mentioned that it is an OTA. The presence of four
> OTAs implies to me that it is a COTA filter, which fits together with
> what I remember about the demos.
> 
> One good thing about this situation is that I have multiple sets of
> boards for this synth: I have got the one keyboard, and I have got two
> pretty much complete sets of boards as bare parts. Of course, none of
> them work.
> 
> Any clues, guys?
> 
> Please help!
> 
> Damian
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