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

Mon Nov 8 18:09:40 CET 2010

Hi,
thanks for your reply. I'll investigate the 12V, maybe some of the
filter caps are dried out or broken..

The 15V is available on the Left connector, on pin 2.

I wonder very much about that 3.69 thing on pin 6. I have traced
around a bit, and there's something which I don't understand: Left
connector pins 6, 7, 8, 9 go through parallel resistors to a single
node. That node is then coupled with a "yellow drop" to a resistor
which goes to the -13.23.. really weird! I think it might be possible
that one of the cards is broken, and breaks the voltages for all the
other cards. For example maybe the "yellow drop" is broken on one of
them. It's a weird part too: looks like a yellow drop capacitor,
kinda, however the marking on it is 104M and every one of them that I
measure with my DMM shows 11 or 9 kR. Time to investigate by swapping
some cards in and out... So anyways I think the -13.23 and Left pins
6-9 are somehow tied together in their failure mode. I think they
might be what's broken.

Cheers,
D.

On 08/11/2010, 3 vcos <moonmuseum at hotmail.com> wrote:
>
> If I had to take a guess...
>
> It seems very strange that the voice cards get -12v and -15v.  The poor
> -12v signal is another bad sign.  Considering you did a repair to a 15v
> supply without a schematic and you aren't seeing 15v on the voice card I
>  would start by investigating if that shitty -12v supply on the card
> should be +15v or at least why the cards aren't getting positive voltage
>  (ok, I'm guessing the +5v on the card is needed as a digital supply).
> Seems like the lack of a positive supply voltage on the card fits with
> some of your other findings as well.
>
>
>
>
>
> Good luck.  I've always been curious how the Tiracon sounded.
>
>
>
>> Date: Mon, 8 Nov 2010 15:21:03 +0100
>> From: cheater00 at gmail.com
>> To: synth-diy at dropmix.xs4all.nl
>> Subject: [sdiy] Tiracon 6V - Vermona / VEB Cottbus - Help and
>> Schematics	Needed
>>
>> 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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