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

Mon Nov 8 18:23:44 CET 2010

Some more news:

I have pulled out all the cards and the voltages stayed the same: on
Right pin 6 -13.23 and 3.69 on Left pin 6.

I have also identified that the Left pin 12 also carries the gate with
it, like the Right pin 5. The Left pin 12 has -12.6V for "off" and
-12.8V for "on".

On another note, I shorted two pins with my probe, there was a "crack"
heard somewhere and the whole synth shut down. Now the analog board
test LED doesn't light up.

Seems the analogue 5V and the bipolar 15V supply are gone. I think I
need some new fuses. And fuse holders. The holders have literally
disintegrated in the last 20 years!

Cheers,
D.

On 08/11/2010, cheater cheater <cheater00 at gmail.com> wrote:
> 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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>>
>