Fried diode now the pedal doesn’t turn off

[Locrian99]

Hello,

Ive got a fried diode in a rocktron zombie distortion.
The pedal currently is always on, led always on, effect always on.   It appears to be some sort of buffered bypass but i cannot find schematic for it.   And the traces are very burnt.   I tried connecting a 5817 in the way I thought was correct but it just made the circuit no longer receive power.   

Im assuming this is using a zener or something as a switch.   Could anyone enlighten me as the way this likely is wired.

Thanks

[Rob Strand]

Im assuming this is using a zener or something as a switch.   Could anyone enlighten me as the way this likely is wired.

If you look at the threads on freestompboxes on Rocktron pedals, the pedals tend to use a reverse silicon diode for protection either 1N4148 or 1N4004 (better).   That would explain why the tracks fried when someone plugged the wrong polarity or AC into it - I'd even guess a 1N4148 which fried short.

The solution is more about rebuilding the burnt traces.    If you find some IC's powered by +9V and ground you should be able to follow the tracks back close to the input socket.  Perhaps to a large (100uF or so) cap across the supply.   Use the DMM continuity tester.  Once you get that far, and using the DC socket as a guide, you should be able to bridge between the DC socket and the rest of the circuit.   You would also expect the silicon diode to be across the supply, but in reverse as it's a parallel reverse polarity protection diode.
I can't see any IC's maybe a regulator?  otherwise you will need to work out the power rail from one of the transistor stages.

[Locrian99]

Im assuming this is using a zener or something as a switch.   Could anyone enlighten me as the way this likely is wired.

If you look at the threads on freestompboxes on Rocktron pedals, the pedals tend to use a reverse silicon diode for protection either 1N4148 or 1N4004 (better).   That would explain why the tracks fried when someone plugged the wrong polarity or AC into it - I'd even guess a 1N4148 which fried short.

The solution is more about rebuilding the burnt traces.    If you find some IC's powered by +9V and ground you should be able to follow the tracks back close to the input socket.  Perhaps to a large (100uF or so) cap across the supply.   Use the DMM continuity tester.  Once you get that far, and using the DC socket as a guide, you should be able to bridge between the DC socket and the rest of the circuit.   You would also expect the silicon diode to be across the supply, but in reverse as it's a parallel reverse polarity protection diode.
I can't see any IC's maybe a regulator?  otherwise you will need to work out the power rail from one of the transistor stages.

I wont have time this morning before work to attempt it.   Im fairly certain i hsbe the traces right.  But with the 5817 i lost power.   Would the 4148 act different or would just have the anode and cathode reversed of the diode cause that.

From the dc socket the trace runs from the sleeve (+9v) to the diode and down to a 50r resistor then to the 100u filter caps.    I had the anode at the +9v trace, the kathode side was connected on a trace to the negative side of the 100u caps.

IC's are hard to see bt cause they all sit under the pots.   







So with the 5817 the anode hooked up to the red trace (+9v from the jack) and the cathode to the black trace which runs to (the negative side of the power filter caps).   I ended up losing power.   Did i just have the a/k reversed?   Or was the type an issue? 

Thanks

[Rob Strand]

So with the 5817 the anode hooked up to the red trace (+9v from the jack) and the cathode to the black trace which runs to (the negative side of the power filter caps).   I ended up losing power.   Did i just have the a/k reversed?   Or was the type an issue? 

The 1N5817 should work but there's no advantage using it over a 1N4004 etc for parallel protection.

You can see some of the tracks and diode (D7 1N400x) direction here.
https://hgecontraptions.blogspot.com/2014/11/repaired-rocktron-zombie-and-mxr-phase.html

The positive from the DC jack goes to the bottom terminal of the diode which is the cathode.

The center leg on the DC jack socket goes to the battery+.  Probably doesn't go to the diode.

The left most connection is the DC jack negative.   Can't see on the pic but it could go to ground, or, it will go to the switched ground terminal on the input jack.

The diode anode will connect to the ground on the PCB, that should also be main ground going to the all the components on the PCB.   The ground from the PSU is via the input jack, the other side of the input socket switch (for stereo sockets there's no real switch contact).

[Locrian99]

Alright sounds like i had it reversed.  Perfect thank you.   Ill have to see what the issue with the switching is next.