Ross chorus super low output

[demarcos]

Hi! I'm repairing a Ross Chorus pedal. The pedal works, the effect is correct when pressing the pushbutton and stops when pressing again. The problem is that in both on and off modes, the volume is extremely low, much lower than connecting the guitar directly to the amp.

I have been checking wiring and capacitors and they seem to be fine. There is an internal 10K potentiometer that does increase the signal from the pedal, but curiously if I use this potentiometer to increase the gain, the pedal stops doing the effect and sounds like a direct signal with no effect.

Any idea what might be going on?

Another curiosity observed is in the chips:

In RC4558 all ok
In TL022 the measurements are fluctuating, but it's still normal.
In MN3101 and MN31007 according to the datasheet pin 1 is GND but I have 9v in both.

Thank you in advance for any help received.

[ElectricDruid]

Welcome!

The MN3101/3007 use a *negative* supply, so you often see them wired up "back to front" with 9V to the "Ground" pin 1, and ground to the "Vdd" pin 3. So that sounds like what you're looking at.

Everything else seems normal.

We need a schematic or we're just guessing.

[demarcos]

Thanks for the quick reply!!! totally agree, you can see that detail by looking at the boss schematic which is similar. i attach this schematic.

[DIY Bass]

The trimpot you are talking abou tis probably the bias trimpot.  Thee is a small range in which chorusing will occur and the rest of the range it won't.

Chorus is basically a modulated delay signal added into the clean signal.  In a pedal that is not true bypass the clean signal is on all the time (and forms the bypass sound).  Turning the effect on turns on the delay and mixes it in.  If your bypass signal is quiet, then that is the path from the input jack to pin 7 of IC1 in your boss schematic, and then from there skip over to pin 2 of IC1 and to the output jack.  I would use an audio probe to trace through this and see where the signal gets bad.  Work on fixing the clean/bypass signal and then worry about the delay if you still need to.

[demarcos]

it seems absolutely logical to do it as you say, thank you very much DIY Bass