MXR Distortion III problem

[The Guitar]

My buddy asked if I could fix his MXR. He got it from his band mate, and when they went to show him it, plugged the pedal into the wrong plug(a 12v) and it popped the C9 cap. Its a 100uF cap from what I looked up and replaced with a 100uF 25v. Tested the pedal with a 9v battery then with a 9.6v plug from my DOD Tec4x, the led lights, but no signal when engaged. In bypass, I can hear the amp. So I tested and replaced C7(4.7uF 50v) and C8(10uF 50v), and D3(1N4700 diode) and still no audio when engaged. I also checked the transistors and got readings from all 5. At this point, I'm kind of stumped. Any help is appreciated!

 

[Chistopher]

Did the reverse polarity protection diode get cooked?

 

[marcello252]

9 to 12 is not that huge to fry everything, double check and eventually replace every electrolytical caps, then check voltages at pin 8 of the opamp, must be in the 8-9 range

 

[The Guitar]

Did the reverse polarity protection diode get cooked?

If it's the diode that's D3(right next to the plug in and C9), yes it did.

 

[marcello252]

3v is not enough to fry that diode, it is necessary to reverse polarity keeping the supply connected for a long time, are you sure about what happened first? Because it could change the place to look at for damages

 

[The Guitar]

3v is not enough to fry that diode, it is necessary to reverse polarity keeping the supply connected for a long time, are you sure about what happened first? Because it could change the place to look at for damages

I'm assuming it got fried since I wasn't getting any reading from it, but would on the new diode.

 

[The Guitar]

Here's the reading from the 10 caps;
C1 - 4.40
2 -
3 - 4.40
4 -
5 -
6 - .65
7 - 4.40
8 - 8.50
9 - 8.83
10 - discharges to 0
I know C4 is a filter cap and from a modding standpoint, can be removed/replaced to change the sound. Not sure if C2 and 5 are like that.
Then the OP Vcc is 8.86, and Vee is also 8.86.

 

[justFred]

I have found this a helpful guide to troubleshooting pedals

https://www.diystompboxes.com/pedals/debug.html