Ok pedal and electronics experts, help me figure this one out

[metropolis_4]

I bought a Pettyjohn ROUS on my way to rehearsal yesterday.

At rehearsal I removed an LPD pedal from my board and put the ROUS in its place, connected to a Cioks DC7 standard Boss polarity at 9v. No signal passed through the pedal and when it was turned on it made a constant high pitched squeal that changed pitch when I turned any knobs or flipped the swamp/fire switch.

I tried a couple different outlets on the DC7 and got the same result.

At home today I tested it with a different setup:

Cable -> pedal -> cable -> amp

I used a different amp, and I used a D’Addario 9v 0.8A power supply. I got the same result.

I plugged a few different pedals into this setup and all of them worked as expected.

I then tried a no-name 9v 1.0A power supply. Again every pedal worked as expected, except the ROUS which squealed the same way.


So…

I returned it to the store and told them it wasn’t working… they plugged it direct into a mixing board and powered it with a cheap no-name 9v 2.0A power supply… and it worked perfectly


I am completely baffled! What could cause it to consistently NOT work under the circumstances I tested it, and then suddenly work perfectly at the store???

 

[SillyOctpuss]

Did you bring it home again or did they keep it? Is it working from your psu now?

 

[metropolis_4]

Did you bring it home again or did they keep it? Is it working from your psu now?

No, I returned it. I figured it doesn’t do me any good if it works at their store, I need it to work with my rig.

 

[SillyOctpuss]

No, I returned it. I figured it doesn’t do me any good if it works at their store, I need it to work with my rig.

Just wondered if you still had it. Surely it's got to be an intermittent problem if you tried it with two different power supplies and with no other pedals the second time.

 

[la szum]

My past experience with squealing pedals is when they are being supplied power that is under
their voltage requirement.

 

[metropolis_4]

My past experience with squealing pedals is when they are being supplied power that is under
their voltage requirement.

Maybe, I can’t believe a simple Rat circuit could require more than 1.0A though.

Those pedals have some internal rail circuit that doubles the power. I wonder if something was wrong with that part of the circuit and somehow the extra amps from the 2.0A power supply were enough that it didn’t squeal?

 

[Boudoir Guitar]

Maybe, I can’t believe a simple Rat circuit could require more than 1.0A though.

Those pedals have some internal rail circuit that doubles the power. I wonder if something was wrong with that part of the circuit and somehow the extra amps from the 2.0A power supply were enough that it didn’t squeal?

"extra amps" doesn't happen. The power supply provides a constant voltage; the pedal circuit is a set load, and the power supply then pretty much just acts as a reservoir of current with the circuit pulling whatever current is needed to satisfy the "current" part of the voltage = load x current equation.

It says it's a true bypass pedal, so the no signal passing bit when it is turned off is weird, suggesting something wrong with the switch, maybe.

I had a King Tone mini fuzz that I could not get to work at all at home. Tried everything. Returned to reverb seller (a shop) and got a "uh, it works fine for us" message once they got it back. I know I wasn't being an idiot. I blamed the phase of the moon

 

[SillyOctpuss]

According to pettyjohn it needs max 100ma, there must be an intermittent problem

 

[gearJunkie]

The only time I experienced the pedal behavior you described (high pitch squeal) is when I daisy-chained my Harmonious Monk after a Pantheon overdrive from a single outlet of a Cioks DC-7. The combination could not receive enough current, and when coupled to a high frequency switching power supply, high pitch squealing commenced.

I moved the HM to its own output and the squealing disappeared. Low current was the issue. Not sure why no signal passed through when bypassed, unless it was dependent on an under-powered gate or relay circuit.