E&MM Synwave Debug

[FUZZZZzzzz]

I've build a E&MM Synwave.

info:
http://www.muzines.co.uk/articles/synwave-percussion-trigger-effects-unit/2682

schematic:


errata:Insert C12 between junction of C6, R12 and junction of R16, TR4 base, deleting existing connections to TR1 collector.

This should be corrected on the pcb as many people build it. I've etched my own from this layout on the website with a little touching up:



Yesterday I had all the wiring with additional alligator clamps (i don't know how you call them) and I got some sound and could control at least the pitch and volume, but after cleaning up the wires today nothing anymore.

I checked for continuity on both grnd and 9v also checked for traces missing traces and part placement. I got some sounds earlier on but have not been able to replicate any of them.

All parts are original no replacements.

Battery: 9,3V
All pots fully clockwise
Attached lead to ground and measured the following:

TR1 BC109C (tab is E):
E  0V
B 5,7V
C 9,3V

TR2 BC109C (tab is E):
E 0,02V
B 0,07V
C 9,3V

TR3 BC109C (tab is E):
E 0V
B 0,03V
C 9,3V

TR4 BC109C (tab is E):
E 0,4V
B 1V
C 4,49V

TR5 2N3711:
E 0V
B 0V
C 7,48V

IC: (Ive used a ca3080 but a can version instead of a dil8)

1. 8,33V
2. 7,67V
3. 7,67V
4. 0V
5. 5,06
6. 9,26V
7. 7,5V
8. 0V

Something seems way odd. Measured without hitting the piezo. When hitting X1 (the piezo trigger) most of the voltages rise. Is this because of the sound triggering nature of the circuit?

Im still learning how to do this.

thank you!

[garcho]

Well, I can't help much, and I might be wrong, but maybe I'll spark something in your head or someone who knows more than me (most of us here) will chime in.

When you whack the piezo, it sends voltage down the line that turns on TR1/2. There are diodes insuring the current is positive polarity, resistors to protect the I_ABC input, and caps for timing/duty. This is controlling the OTA, which is acting as a VCA in this setup. There's a resonant filter section (TR4 and pitch control) and a noise generator (TR5) that are the inputs getting mixed and out the OTA output to the output jack.

Regarding pin 1 on the OTA, why is there voltage there? I don't believe it should matter, because I don't think that pin is connected to anything internal, but I could be wrong.

Pin 5, the (amplifier bias input, the magic of OTAs) is usually the scene of the crime, and judging by your voltage there, your IC is kaput. Much more than 1mA and the magic smoke is released.

Try doing a search like this: "3080 iabc current voltage site:diystompboxes.com"

[FUZZZZzzzz]

thank you for this:
https://www.diystompboxes.com/smfforum/index.php?topic=63724.0

thanks for the explanation. i have been wondering about the voltages on the ic where its not connected to the anything. lots to read

[anotherjim]

^
Note the OTA inputs fed from a voltage divider - should be half supply voltage. If it isn't, take the chip out and check the voltage again. If it's now half, the chip may well be no good. If you have a rare/expensive/hard to get device, it's always a good idea to fit a socket and check the connections and voltages *before* you test with the chip in. If in doubt what they should be - ask!

[FUZZZZzzzz]

That's a good thing to start doing from now on I will take the chip out, measure again and report back. thank you!

^
If you have a rare/expensive/hard to get device, it's always a good idea to fit a socket and check the connections and voltages *before* you test with the chip in. If in doubt what they should be - ask!