Build Your Own Clone Message Board

I have a pretty old OD2 that I built about 15 years ago. It has worked wonderfully for me.

Until I accidentally used a bad power supply on my board the other day. It seemed like it underpowered the board. None of my other pedals have been affected, but the OD side of the OD2 went completely silent.

The LED action works, bypass works, boost side works. The problem only occurs when the OD pedal is switched on.

After replacing the opamp, the issue then changed to the OD side working normally, but being very quiet. The pots all affect the sound as expected, except for the fact that I cant get the volume to a usable level anymore.

I know that the issue might be a cold solder joint, but the pedal has been in use for pretty much the entire time. So I wanted to see if there might be another explanation. Are there any components in the OD2 that might fail silently beside the opamp? I see no evidence of burned components.

I have switched the opamp with three other opamps to make sure that the it wasnt still the issue. The problem persists when using plugin power and battery. EDIT: I have also confirmed that the footswitch has continuity as expected,

I am still looking for a possible bad solder join, and I will continue to until this problem is rectified.

Are you using the regular transistors or did you do the MOSFET mod?

_________________
*patience is a virtue*

Please do not PM me. email is prefered. keith@buildyourownclone.com

I did the MOSFET mod.

It's possible the BS170 (in the buffers, not the clipping) are damaged as well. BS170 or 2N7000 will work as a replacement.

_________________
*patience is a virtue*

Please do not PM me. email is prefered. keith@buildyourownclone.com

Ok, that is good info. Is there a way to verify that they have failed, or is it customary to just replace them?

And where is the buffer vs clipping?

You could probably tell by taking voltage readings.

The buffers are the transistors that AREN'T sandwiched between the clipping diodes and LEDs.

_________________
*patience is a virtue*

Please do not PM me. email is prefered. keith@buildyourownclone.com

I purchased some 2N7000 N-Channel MOSFET TO-92 from ebay, and replaced all the MOSFETs (except for the two right next to each other right next to the empty LED slots). Now both the boost and the overdrive are dead. The boost worked fine before.


I still get LEDs and clean bypass. Did I buy the wrong transistors? The seller on ebay seemed legit, so I dont think I bought bum transistors.

You really can't trust buying any sort of discrete through-hole FETs from ebay, or amazon, or even several electronics vendors anymore. You should have taken voltage readings first.

I guess the upshot is that now since you've replaced the BS170 in the boost channel that was working before, but isn't anymore, it makes it seem more likely (but not absolutely certain) that the BS170's were your problem.

We have them in stock. Mouser and Digikey have them in stock as well. I would be skeptical about buying them from anywhere else.

_________________
*patience is a virtue*

Please do not PM me. email is prefered. keith@buildyourownclone.com

the BYOC site shows them as out of stock, how can I order some?

NOW THATS WHAT I CALL CUSTOMER SERVICE!

I'm back. I installed the mosfet transistors as recommended.

1. Boost is back, so yay!
2. OD is still super quiet, so it looks like I'm back to square one.

Some points of interest:
1. Turning on and maxing the boost volume while overdrive is on does not affect the volume of the overdrive.
2. I can hear the overdrive distorting my signal, and messing with the internal trimpots does seem to still affect the tone of the distortion. I can turn the LOUDER trimpot all the way up and get the screeching noise, just at a very low volume.
3. Switches seem to make no difference, but its at a low volume so i cant be sure.

Could this be a footswitch thing? God I hope not. I hated soldering those things.

You should take voltage readings of the Op Amp and the MOSFETs on the OD side.

_________________
*patience is a virtue*

Please do not PM me. email is prefered. keith@buildyourownclone.com

Do you have recommended guides on how to get readings from them? I can use a multimeter, but both the MOSFETs and opamp have multiple terminals, and I am not sure what kind of readings I am looking for.

You need to take a DC voltage reading on each of the pins/legs, referenced to ground. Here's how:

Set your multimeter to the DC voltage mode, indicated by a solid line above a dotted one. Use the 20VDC range setting if it's not an auto-ranging meter. Your power source needs to be connected and there needs to be a cable in the input jack. If the pedal is assembled into the metal enclosure, put the black probe into one of the corner screw bosses of the enclosure--this is your ground connection. If the "guts" are out of the enclosure, use the sleeve tab of the input jack for the ground connection. Then touch the red probe to each point that you want to measure. See left side of the image below for the numbering of the IC pins. MOSFET legs will be drain, gate and source per this diagram: https://www.componentsinfo.com/wp-conte ... valent.gif The drive-side MOSFETs are Q1 and Q2 as shown on the PCB map below.

_________________
“My favorite programming language is SOLDER” - Bob Pease (RIP)

My Website * My Musical Gear * My DIY Pedals: Pg.1 - Pg.2

The values are the same when the OD side is powered on or off. Not sure if that means anything.

opamp numbers
1. 4.5
2. 4.5
3. 4.5
4. 0.0
5. 4.5
6. 4.5
7. 4.5
8. 8.98

Q1
S. 2.39
G. 2.97
D. 8.98

Q2
S. 6.75
G. 8.96
D. 8.96

No, it doesn't. The circuit is powered as long as a power source is connected and there's a cable in the input jack. The footswitch just switches the effect circuit in and out of the signal path; it's NOT a power switch.

Your op amp numbers are spot-on. I'd expect the two buffer MOSFET voltages to be closely comparable, though, and those differ substantially. But I don't have a MOSFET-modded OD2 here to do a test comparison. Hopefully Keith will stop in and have a good idea of what's going on there from those voltage results.

_________________
“My favorite programming language is SOLDER” - Bob Pease (RIP)

My Website * My Musical Gear * My DIY Pedals: Pg.1 - Pg.2

Your problem is at Q2. It looks like D8 is bad. It looks like it's allowing too much +V into the voltage divide at the gate of Q2. D8 would be the diode closest to the boost foot switch, with the square solder pad sort of between eyelets 1 and 5.

_________________
*patience is a virtue*

Please do not PM me. email is prefered. keith@buildyourownclone.com

Is it where D6 is on the above schematic?

Yes, it was mislabeled as D6 on the PCB map I posted above.

_________________
“My favorite programming language is SOLDER” - Bob Pease (RIP)

My Website * My Musical Gear * My DIY Pedals: Pg.1 - Pg.2

Thank you guys! The diode in question was the culprit. Thank you for your patience, I am happy to have the OD2 back on the board.

Great! Glad to hear that did the trick!

_________________
“My favorite programming language is SOLDER” - Bob Pease (RIP)

My Website * My Musical Gear * My DIY Pedals: Pg.1 - Pg.2