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TM3030 problem with trigger and sound
MUFF WIGGLER Forum Index -> Oakley Sound Systems Goto page Previous  1, 2 [all]
Author TM3030 problem with trigger and sound
Synthbuilder
studyman wrote:
so, i did the mesures with a new voltmeter,
switched power on thru R5: DC= + or - 8,20V and AC: 17V or 0v if i inverse the pointers...


That AC one is very odd. Can you measure it again. Leave it for a few seconds to stabilise. If you are indeed getting a value over 0.5V then your VCO is probably working. The fault is probably elsewhere in the circuit.

Tony
studyman
Hello,
i've just put the J201 and i've got th real sound !!!! great !!! BUT the sound of the 303 is with a big white noise on every notes !!
what's this next problem...?
Pierre
Synthbuilder
studyman wrote:
i've just put the J201 and i've got th real sound !!!! great !!! BUT the sound of the 303 is with a big white noise on every notes !!


White noise as in a loud hiss? If so, can you filter it with the cut-off and resonance control?

If the hiss does not change in tone when these controls are altered the fault is probably somewhere in the VCA or output stages of the filter. However, changing the J201 should not have affected this unless you have an intermittent fault somewhere.

Tony
studyman
hello,
effectively, this is a loud hiss and it doesn't change in tone when i cut the freq and reso
Pierre
Synthbuilder
Sorry Pierre I think I may have misunderstood your post above. So the TM3030 is now working as it should but with an additional hiss on top of the correct sound. Is that right?

If so, does the hiss turn on and off with the notes being played? Or is the TM3030 constantly hissing?

If it is always hissing you probably have a fault in the output circuitry. That is the circuitry around Q33 and Q34. Also Q35 could also be bad.

If is only hisses when the notes are being played then the fault could be in the VCA. Possibly U14 or U15.

Tony
studyman
hello,
i measured again the AC thru R5 and it's 18V in one way and 0v in the other way...
Pierre
studyman
yes hiss is only when the note is played
studyman
it's very strange because i measured R5 solded it's 2,8ohms and i unsolded it it's 10k !!!
studyman
2,8k...sorry
studyman
i've got the same problem with R3, on the board 14K and off the board 180K...i don't understand anything.... very frustrating
Synthbuilder
It is not possible to measure the resistance of any component while it is soldered into a circuit. All the other components connected to the resistor, and there are many, will have an affect and lower the actual value read on your meter. The only way you can measure resistance is to take the component out - although you can sometimes just lift one leg and measure between the lifted leg and the other end.

This is generally why we measure voltage around a circuit. But to understand these voltages you normally need a good knowledge of the operation of the circuit.

If your meter gives one AC voltage one way and another the other way then it is a poor meter. Sorry. All it is actually doing is measuring a DC voltage through a internal diode. It's really too simple for doing accurate measurements. Better meters are available that will measure it properly.

If you are hearing a hiss only when the notes are being played and not affected by the filter then I would suspect the VCA - this is either the CA3080 or the BA662.

However, it could be other things. The VCA always produces hiss - all electronic circuits do. If the audio level going into the VCA is somehow smaller than it should be then the hiss will start to be heard. Maybe R110 is the wrong value?

Tony
studyman
R110 is good, 2,2K, i'll try with a new CA3080 that i found in deutchland...
thanks for your patience .....wink
Pierre
studyman
yyyyeeeeaahhhh ! because you said that's possibly the VCA i cod the J201 (the buffer for the CA3080) if i understood the circuit....and that's it i ve the sound without the noise !!!!!! great great !!!!!! thanks Tony !!!!
nanners nanners nanners nanners nanners nanners nanners nanners nanners nanners nanners
Pierre
Synthbuilder
thumbs up
IKE753Z
I'm tracking down a very similar issue, as far as I can tell VCO is working correctly, waveforms look good and it has that wonderful 303 sound, but at the start of every single note (excluding slides of course) I get a massive click, like so:


I know full well that I was ripped off when I bought my power supply, forked over the money for a 24VDC 1A linear supply and got a 24VDC 600mA switch mode power supply instead. very frustrating

The only thing I can do to change the shape of the click is by adjusting the decay, in which case I can make it slightly longer.

Do you think this is caused by the power supply not providing power fast enough or do you think it's a problem with the VCA? All other voltages seem to be fine, I'm mildly suspicious that the 2SK30Y is not working correctly or is fake, but I wanted a second opinion before I started throwing more money at it.
Synthbuilder
It could be the power supply. Check your voltage readings on the 12V and 5.3V supply lines. If these are dipping obviously as a new note is triggered it is the power supply.

The TM3030's own power supply should filter out most of the noise present on any external supply.

The other thing to check is the waveform of the VCO as each note is triggered. If you continuously hit the same note then you should not see the VCO frequency change. In that scope trace shot it's difficult to see whether the VCO is changing or the output of the VCA is being affected by a very temporary large DC shift. If it is the VCO pitch that is changing, look for faults around the glide circuit particularly U8.

Tony
IKE753Z
Reporting back for the sake of those troubleshooting in the future:

Q18 (2SK30A-Y) WAS the problem and since replacing it my TM3030 functions beautifully!

Thanks for all your help and hard work Tony! we're not worthy

The documentation, board quality and technical support for this project was excellent!

The TM3030 is incredible! SlayerBadger!

(I'll probably be getting started on an Oakley modular based on how much I enjoyed this!) Mr. Green

-I
Synthbuilder
thumbs up Good to hear you got it working.

Tony
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