Ross distortion polarity mystery

[Chris oej]

Hi,

I'm trying to fix a Ross Distortion for a friend of mine. The pedal dies when connected to a daisy chain. Once dead it won't work at all, even if powered by a battery. However, if I connect the pedal to a positive ground power supply then back to the intended negative ground it works again.

Does anyone know why this is happening and if there's a way of modding the circuit to prevent this?

Thanks

Chris

[Mark Hammer]

The Ross will have used a mini phone jack for the external source, no?

Keep in mind that while Boss style 2.1mm power jacks are configured as outside pos and pin/tip negative, phone jacks are configured at tip-pos and shaft ground.

What I can't explain is the suppression and resumption of functioning.

[zombiwoof]

Are you using one of those adapter cables that fits the 1/8" pos tip jadk to the Boss type neg center barrel connector cable when daisy chaining?.  You have to do that for the Ross pedal to work with other pedals.

Al

[Chris oej]

It was originally daisy chained to a power supply using positive tip minijacks. I've taken off the 9v socket on the pedal and replaced it with a standard 2.1mm going direct into a regulated 9v power supply - same problem.

I was wondering if the diodes had blow so replaced them (1n4148s) with some 1n914s which i have lying around - completely dead. I replaced the SPDT footswitch and all the wiring - no help.

I'm thinking that it maybe the opamp (RC4558P). Doe you know what the voltages should be on each pin?

Could i replace the RC4558P with a JRC4558D?

I might also replace the diodes with fresh 1N4148s - basically i'd have replaced the every component except the resistors and capacitors.

Thanks

[Mark Hammer]

You can replace the original chip (assuming it actually uses a dual op-amp; the circuit only requires a single op-amp) with any other dual op-amp you want.  They pretty much all have the same pinout.

This pic - http://azear.files.wordpress.com/2011/01/fixit-rossdistortionpedal-3.jpg - shows an RC dual op-amp, with pins 1 and 8 oriented towards the inside of the board, rather than towards the outer edge.