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SOLVED Roboto no output


Active member
Finished the Roboto and I get no sound in active nor bypass mode.

I can't find any obvious faults so I'm wondering if maybe it's the IC chips? I've got 3.3V where it's supposed to be but other than that I don't know what types of voltages or signals I'm supposed to see on the other pins.

Or maybe it's some dumb mistake that I'm just not seeing...

1) Does anything in Roboto need to be programmed? I got the HT8950 from Ebay (China) and the ATTINY from PedalPCB.

2) What does the trimmer adjust / what's the adjustment procedure?




Active member
If you don’t get any sound on bypass, check the 3pdt, breakout board and their wiring to the main board. You are shorting somewhere. Try to make the bypass signal work first before moving on. Also check the jacks and check if the leads are touching when jacks are plugged.

Is the led light turning on/off when active/bypass?


Active member
Yeah the LED turns off and on. I did a continuity check on the 3PDT and the wiring to the PCB, with the switch in the on and off mode. I didn't see anything obviously wrong, but I'm kinda guessing about how it's supposed to operate (where I should and shouldn't see continuity with the switch on vs off and which wires I should be comparing). What's the general procedure to check this?


Staff member
In bypass you should get continuity between the Tip connections of the Input / Output jacks.

If you DON'T have continuity:
Check for continuity between the Tip lug of the Input jack and the bottom left lug of the 3PDT.
Make this same measurement between the Tip of the Output jack and the bottom right lug of the 3PDT.
If both of these connections have continuity, check between the bottom left lug and bottom right lug of the 3PDT.

If you DO have continuity, make sure you DON'T have continuity between either jack Tip and ground.


Active member
Hey I just wanted to circle back to this because I found that pedjok's photo provided the solution... the output jack was touching the case. It was a really simple fix. Once I did that it worked perfectly. I wasn't sure if I'd like the sound of Roboto, since the demos of the original pedal on youtube sounded kinda trashy but man once you dial it in this pedal gives a really nice distortion sound -- not at all what I expected.

Thanks also to PedalPCB for the troubleshooting tips which gave me some new skill to know where to trace I/O problems. So far all my build troubles have been really simple stuff like this, and nothing has caught on fire yet! :)