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TM3030 - low voltage output - the PSU doesn't responding
MUFF WIGGLER Forum Index -> Oakley Sound Systems  
Author TM3030 - low voltage output - the PSU doesn't responding
rubengarcia
Hi there, I just finished my TM3030, doing the calibration I notice that the PSU doesn't work correctly. All parameters and leds are working fine. But I can't fix a good tune or octaves. I guess It's because the voltage output, using a voltage tester between +5V3 and GND holes, there appears 3'97V. I tried to change that using the PSU trimmer but nothing changes.

Any idea about it?

Thank you so much in advance.

Ruben.
Synthbuilder
What's the voltage across the GND pad and pin 12 of U10? It should be above 17V. If not you may need to try another power pack.

If that is fine, what is the voltage across the GND pad and pin 3 of U10? It should be around 15V. If not check the values of R40, R50 and R60.

Tony
rubengarcia
Hi Tony, thank you for your fast reply, I measured that and here you go the results:

across GND and pad pin 12 U10 - 0V
across GND and pad pin 3 U10 - 11'8V

What do you mean about change the power pack? The power supply?
I tested my power supply @ 15V is giving 14'9V and 1800mA.

Thank you
Synthbuilder
rubengarcia wrote:
I tested my power supply @ 15V is giving 14'9V and 1800mA.


Is that DC? If so, it's too small. You need 18V there. That would explain the lack voltage at the +5V3 pad.

If it's AC, then check pin 12 of U10 again. It has to be more than 17V to allow the TM3030 to work properly.

The TM3030 requires either a 15V AC or an 18V DC power pack to work.

Tony
rubengarcia
Cool I tried that, now I understand how it works. Finally to fix it I'm using 19V at the power supply, now +5V3 and GND are giving 5'32V with the PSU trimmer at the end of its turn.

pin pad 3 U10 is at 15'5V
pin pad 12 U10 is at 17'5V

Now the sound is a bit more louder, resonance more sharp and octaves on their places.

But I notice another issue, maybe it's about MIDI programation, but having the cut off pot totally open, the FREQ trimmer totally open, the filter sounds a bit matt, the strange thing is I can open the filter more using the modulation wheel at my keyboard, is it normal?

Thank you so much Tony, I can't wait to show you the metal case I made.
Synthbuilder
rubengarcia wrote:
... but having the cut off pot totally open, the FREQ trimmer totally open, the filter sounds a bit matt, the strange thing is I can open the filter more using the modulation wheel at my keyboard, is it normal?

Yes, this is normal behaviour for the TM3030. It copies the TB303 faithfully so the only way to get the filter to open fully is to use the envelope signal via the depth pot - usually with a longish decay time. Unlike the stock TB303, the TM3030 (and midibass fitted TB303s) can also use the mod wheel too.

Tony
rubengarcia
Thanks a lot Tony and congrats about your devices!
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