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TM-3030 problemo
MUFF WIGGLER Forum Index -> Oakley Sound Systems  
Author TM-3030 problemo
the bad producer
Hello,

A friend of mine just finished his TM-3030, which worked and sounded amazing - just exactly to my ears the same as an original side-by-side...

Anyway, we tested it on the bench, but since he put it into an enclosure it has died, I can't figure out why though...

The slide light is always on, all chips seem to be getting power, but there is no audio output, I think it is oscillating, but not getting any note info from MIDI, so the gate LED does not light...

He did say that the waveform switch broke (he pulled it apart whilst soldering it) would that affect the circuit after it had been replaced? Also, whilst it was working (the second time - in the box) it sounded a bit 'warbly' ie the pitch seemed to quiver around rather than be clean, if you know what I mean...

Anyway, if anyone has any ideas on what the problem could be please let me know!

Charlie
Synthbuilder
Unfortunately there could be a variety of reasons why it doesn't work. However, I would look again at the wiring of the midi sockets, output and power supply inlet.

The power supply inlet should really be of the insulated type - ie. made from a plastic housing and not attached to the chassis with a metal bush and nut.

Most switches can't be fixed up again if they break. The little slide types can be sometimes fixed, but they're never as reliable as new.

Warbly pitch may indicate a problem with the power supply wiring. Perhaps there is an internal mains transformer too near the TM's VCO circuitry.

However, a slight warbly pitch can also happen if the TM3030 is fitted to a metal case and the case is not grounded, ie. it's left completely floating. It is normally a good idea to have the audio output ground connection tied to the metal casing which grounds the casing very well.

Tony
the bad producer
Hi Tony,

Thanks, I checked it out last night, it is in a plastic case with a metal front panel, all sockets are in the plastic bit (audio, power, MIDI).

I had a look at the soldering, and checked the wires to the pots, and managed to get it working properly for a while, I'd taken the pots and switches off the panel to work on it and tested it without the panel. After attaching the panel again, it has stopped working.

This is what happens:

Power on, slide and power LEDs lit
MIDI sequence entered
TM-3030 plays for about 5 seconds, then gradually dies....
No audio output (checking with voltmeter), but slide and gate LEDs still flashing (I assume it is still receiving MIDI)

So I guess the MIDI works, the power works, but the actual audio is strangely disappearing, the odd thing is that even without turning it off, just stopping and restarting the external MIDI sequencer means that the audio starts again, and then fades away....

I'm really stuck on this, is it possible to PM the schematic, then maybe I can trace the signal and see where it is going? I also checked continuity between all the pots, switches etc and the panel, nothing is shorting there..

Anyway, sorry to bore you, but hoping you may be able to help!

Charlie
Synthbuilder
the bad producer wrote:
So I guess the MIDI works, the power works, but the actual audio is strangely disappearing, the odd thing is that even without turning it off, just stopping and restarting the external MIDI sequencer means that the audio starts again, and then fades away...


That's a weird one for sure. Dead Banana

But I'm thinking something to do with the VCA EG. Or maybe the gate signal is not going low for long enough within the TM3030. This would suggest the gate trigger circuit caps are wrong. But if it worked when not in the case it can't be a component value being wrong so I'm puzzled.

Actually, you aren't playing notes in legato fashion are you? There is no sustain in the TB303's EG circuits so you need to make sure there is a suitable gap in between the notes for them to be heard.

E-mail me, address on the contacts page at the site, and I'll send you the schematic.
the bad producer
Hi Tony,

It is now working!, thank you for your support...

I resoldered most of the parts, took all the chips out and resocketed them, and now it works super-fine! I think a couple of the chips had not been pushed in etc..

I think that a couple of the pots had been heated til their doom when being soldered - the env mod pot certainly had died!

I appreciate your offer of the schematic, as I have just reread the FAQ's on your site and see that you offer them at a small charge - so thank you for the kind offer!

I look forward to finishing mine, and having three 303's (the 3030 sounds to my ears exactly like the original!) in the studio!

Thanks,

Charlie

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