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Help with Transcendent 2000

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Help with Transcendent 2000

Postby mken » Tue Sep 12, 2017 1:12 pm

Hello, I'm new to this forum and I'm currently trying to checkout (repair) a Transcendent 2000 synth. Its history is I built this for a friend in the 80's and he used it a couple of times then its been stored in his storeroom since then. He's now having a clearout and gave it back to me. I am quite fond of the instrument as I put a few hours into constructing it and ideally would like to sell it but only if I'm sure it is working correctly. The main thing I'm struggling with is to know how the keyboard should work. Currently if I play a note it stays on even when I release the key. If I press another key then that note is played but stays on. So my question is should I be able to play it like say a piano or organ where I get a note when key is pressed but it stops when I release the key. I have the schematic and some test gear ( meter , scope) and the output stays on when key is released. Don't knoiw if this is how it should work or there is a problem. Any info gratefully received.
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Re: Help with Transcendent 2000

Postby desmond » Tue Sep 12, 2017 1:39 pm

Sounds like you might have a long release setting on the envelopes, or have switched the synth into some kind of trigger mode where it no longer uses an envelope to shape the time - ie the amp is always full on, and the keyboard voltage is just changing the pitch.

So check those settings on the synth first before you assume it's faulty.

(I don't know that synth personally, but check those things if the synth has them first.)
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Re: Help with Transcendent 2000

Postby Dave B » Tue Sep 12, 2017 1:48 pm

So it sounds like there is an issue with the 'release' element of the envelope although there is a remote possibility of the decay being the culprit. Looking at a panel image, I can see that the envelope section has options for both the Decay and the Release elements. It's set both to about 12 o'clock and press a key. My _guess_ would be that you would want the switch under the release knob to be set to 'adsr' as that would mean that it would take the value of the release from the knob. My other guess would be to set the Decay switch to 'norm'.

The fact that it is triggering notes suggests that the generating circuitry is working ok. If it's initially quiet until the first key is struck, then I'd turn it off, crank the Attack up to full then hit a key and check that the sound swells in slowly as it should show that the envelope generator is working and controlling the VCA output.

Apologies if this is egg-sucking territory ... just thought it worth checking the basics before hitting schematics...
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Re: Help with Transcendent 2000

Postby Wonks » Tue Sep 12, 2017 2:45 pm

Probably the last slider switch on the right, the ADSR On/Bypass switch. Sounds like it's in the 'On' bypass position in which case the note will stay on. If it's in the 'ADSR' position, then the switch may be faulty and it's worth trying some switch cleaner on it for a start.

My T2000 is still in bits (I keep forgetting about it) so can't help by testing but I've got the original manual and circuit diagrams etc.
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Re: Help with Transcendent 2000

Postby mken » Wed Sep 13, 2017 10:42 am

Thanks for everyones prompt reply. I will be able to spend some time on this tomorrow and will update with my findings. From what's been written so far it seems that once the VCO is triggered it will maintain a "constant" output and it is up to the ADSR envelope to decide how long the note plays for. From the block diagram it looks like the "pitch" signal, one way or another goes thro the VCF and then to the VCA. The VCA can be "modulated" by the ADSR or the ADSR can be bypassed. The VCF has a CONTROL switch which says KB - RANDOM-OFF. So what would be the purpose of the OFF position?
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Re: Help with Transcendent 2000

Postby desmond » Wed Sep 13, 2017 11:20 am

The filter cutoff can be modulated by the Keyboard (filter keyboard tracking), or a sample and hold generator (Random), or Off, in which case the filter isn't modulated by the keyboard or sample and hold, it just follows the conventional use (defined by the cutoff/resonance knobs and modulated by the filter envelope.

More info:
http://www.spontis.se/pdf/t2000.pdf
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Re: Help with Transcendent 2000

Postby mken » Thu Sep 14, 2017 11:45 am

I seem to be getting somewhere. As they say , " a little knowledge is a dangerous thing".
From previous posts and by watching some Youtube videos I now see that the VCF and VCA are extremely important in getting a signal thro the synth to output. I think the panel labelling is a little confusing since it says OFF on the VCF filter implying you're turning it OFF completely whereas it actually means you're cutting OFF the control of the VCF. My previous keyboard experience has been with Yamaha PS keyboards where you select a voice and if the volume is turned up you get a signal. Now it seems with this synth that the Filter and VCA have to be tuned. So I can get a reasonable output now but I am still left with probs I don't understand. The ADSR controls all seem to work but if I play a note then the note sounds but then drops back to very low level whereas I would want it to be completely silent. Also when playing the keyboard it seems to get "locked out" and then will re-enable itself for a while then lockout again. It appears to be connected with the slow oscillator. If I increase the freq of slow osc then the periods of keyboard active inactive speed up. However I don't have any panel switches set to include the slow oscillator! So though I'm making progress I'm far from convinced it is working correctly. As an aside I am going to replace the 4 electrolytics that I can see and then go thro the alignment procedure for which I have instructions. Will keep you updated.
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Re: Help with Transcendent 2000

Postby Rich Hanson » Thu Sep 14, 2017 12:29 pm

i think there's a video on YouTube by Markus Fuller on fixing a Transcendent 2000, perhaps that might be worth looking up.
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Re: Help with Transcendent 2000

Postby desmond » Thu Sep 14, 2017 12:55 pm

mken wrote:I think the panel labelling is a little confusing since it says OFF on the VCF filter implying you're turning it OFF completely whereas it actually means you're cutting OFF the control of the VCF.

That control is in the filter section but i's not underneath the filter cutoff or resonance controls, it's in the filter modulation section, as it's just another filter modulation control. That's just a little manual reading issue, really. I'd really start by reading the docs to work out what everything does before you can question whether the behaviour you are experiencing is incorrect or not.

mken wrote:My previous keyboard experience has been with Yamaha PS keyboards where you select a voice and if the volume is turned up you get a signal.

Well, those things aren't analog synths, they are very different things entirely.

mken wrote:The ADSR controls all seem to work but if I play a note then the note sounds but then drops back to very low level whereas I would want it to be completely silent.

Is the amp envelope sustain set at 0?
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Re: Help with Transcendent 2000

Postby Hugh Robjohns » Thu Sep 14, 2017 1:17 pm

mken wrote:As an aside I am going to replace the 4 electrolytics that I can see and then go thro the alignment procedure for which I have instructions.

It seems a bit rash to go swapping out components just because you can 'see them'! Okay, if the electrolytics are bulging or leaking, fine: they will need changing. But I'd wait until (a) you fully understand how to use this instrument, and (b) you've confirmed something is awry with the alignment before messing about replacing the innards.

Like most analogue synthesizers, there are a number of potential traps and pitfalls in its operation, and most of the issues you've described sound more like finger-trouble issues than actual faults. Mis-setting a control here or there can have quite perplexing results if you're not familiar with the design and its features.

if you don't already have it, the construction and operating information is all in here:

http://www.spontis.se/pdf/t2000.pdf

H
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Re: Help with Transcendent 2000

Postby Wonks » Thu Sep 14, 2017 1:53 pm

Midierror (of this forum) has one, and has done a couple of videos which may well be worth watching.

An overview
https://youtu.be/XFwSZ2_-N3M

Some sound demos:
https://youtu.be/dL59aCTIpoM
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Re: Help with Transcendent 2000

Postby Wonks » Thu Sep 14, 2017 2:13 pm

Here's an example setting sheet that came with the kit that wasn't in the ETI magazine. The brass patch is the more standard musical synth setting and should help get you to a good starting point for 'normal' keyboard sounds.

Image
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Re: Help with Transcendent 2000

Postby mken » Fri Sep 15, 2017 2:40 pm

Hi , thanks for everyones helpful comments, in particular the control panel overlays which I hadn't seen before. Just at the moment I don't feel I have stable base to work from or on which to assume correct or incorrect behaviour. So I decided to try the Brass setup assuming it would be set to play a note as long as a key was pressed and then cease when key released. So with my amp and mixer on but the synth powered off I set the controls as per the overlay for Brass. When I power on the synth I get a tone without pressing any key. It does sound brassy but I hadn't told it to do anything yet. The note persists and will change if I press another key but then this still persists. If I play several keys in a row then I do get note changes but the keyboard stops controlling for a few seconds and the will start again. This is a periodic rather than intermittent response. So i know it sounds like I'm throwing many problems into the mix but currently there is nothing stable in its operation to say OK I understand that bit and it's working and then move onto another problem. So for now I feel I should concentrate on this inability to stop the note playing which I assume is related to the ADSR envelope. In the manual it says if ADSR is bypassed then the note will be continuous. With ADSR switched in the ADS seem to affect the note but the Release pot doesn't appear to curtail the note. As this was built by my own fair hands I think I will spend some time looking at the build and ensure that all components are correctly installed and orientated and where possible do some onboard testing of transistors etc. This may take some time so I may be off the forum until I can give further info. Also looked at Youtube videos which are helpful but do not bring me closer to the problem.
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Re: Help with Transcendent 2000

Postby Wonks » Fri Sep 15, 2017 3:42 pm

It may be a faulty keyboard contact. Each key has two j-wire contacts, one for note pitch and one for a note on/off trigger. If a trigger contact is always being made, then you'll always get some kind of note. But they generally suffer from lack of contact being made, so it's possible, but not that likely.

It's more likely to be something like a selector switch that's faulty. I'd start by seeing if the ADSR on/off switch is working.
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Re: Help with Transcendent 2000

Postby feline1 » Mon Sep 18, 2017 10:09 am

Only just seen this thread (have been busy moving house... so many synths to carry :lol: )

Do you have the original construction notes/manual for the T2000? It includes a calibration procedure... after the synth's been in storage for such a long time, you really need to go through that methodically before expecting the synth to behave! :)
It tells you where to set he controls so you can actually calibrate things without getting confused. For example there's VCA level calibration, which may be what's stopping notes decaying properly to silence.
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Re: Help with Transcendent 2000

Postby feline1 » Mon Sep 18, 2017 10:18 am

The PDF that Hugh linked too it the original magazine article, but not the User Manual, which has a more comprehensive operation guide/ calibration procedure. (Unless I'm totally misremembering) - my copy is on paper, I'm afraid.
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Re: Help with Transcendent 2000

Postby Wonks » Mon Sep 18, 2017 11:22 am

Here's the calibration procedure from the user manual:

Image

I used an electronic guitar tuner to set the octaves.
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Re: Help with Transcendent 2000

Postby feline1 » Mon Sep 18, 2017 3:38 pm

ah that's the one!
IIRC is a bit of a faff to do this, cos you have to take the tops off all the pots and then take the whole silk-screen faceplate off in order to get at the trimpots. But it does work :)
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Re: Help with Transcendent 2000

Postby Wonks » Mon Sep 18, 2017 4:10 pm

I've been semi-tempted to remove those trimpots and wire them to some locking multi-turn pots fixed to the back of the synth. Just not sure whether the wires involved run could introduce some instability in the circuit.

When I took receipt of my T2000, it was just the relative tunings that were out, the wave settings were still fine.
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Re: Help with Transcendent 2000

Postby mken » Wed Sep 20, 2017 8:39 am

Hi everyone, I did post a reply a few days ago but it's not surfaced yet so here is a summary of progress so far. Thanks to all of you that have added useful info / comments. A few mentioned gate problems so I took a look at the keyboard and sure enough one key's gate contact was permanently on. So a little tweaking fixed that. But overall on close inspection I found several keys that were marginal in making good contact so I made a small addition of a small plastic spacer on the end of each key actuator so the contacts now have 1 or 2 mil of overtravel. The next issue I found, and I'm sure it could apply to many 2000s is that when I reassembled it all , when I retested it there was an intermittent crackles that seemed to be worse if I lifted one end of the synth. Eventually traced to the top panel just touching one of the 3 round silver I/c's at rhs of board. These are 8 pin devices that sit in holders and it was left to the assembler to form the legs so they would fit the holder. I don't know if there was any warning given in original instrs about possible interference with the top plate but I don't recall any. So if you were a couple of mm high then the i/c could touch the metal top panel.
Wish I had room to keep it but I think it will be up for sale. Even have the original foot pedal!
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