Author Topic: MXR Disto + Wampler mod DIY issue  (Read 148 times)

Kortes

MXR Disto + Wampler mod DIY issue
« on: November 23, 2018, 09:38:32 AM »
Hi everyone,

I made my own PCB for a MXR disto + with 2 mods from Wampler but that's not working...

I have no sound when the distortion is on...

So after research, I found a several issue :

- I didn't have +4.5v after R2 et R3, I have 2.5V
- at legs of the 741 I don't have the good voltage (preconized by GGG on the PDF about the disto+)

Normal voltage :

0V > 1 | 8 < 0
4.5V > 2 | 7 < 9V
3.6V > 3 | 6 < 4.5V
0V > 4 | 5 < 0v


which i have :

0V > 1 | 8 < 0
9V > 2 | 7 < 9V
0.24V> 3 | 6 < 9V
0V > 4 | 5 < 0v

I test the project with a TL071 for see if the problem came from the 741, I don't have the voltage, but still no working...

This is my schematics

https://preview.ibb.co/mVcGcq/disto.png

Thanks to community,

Kortes

duck_arse

Re: MXR Disto + Wampler mod DIY issue
« Reply #1 on: November 23, 2018, 09:57:07 AM »
hello Kortes, and welcome to the forum. please contact one of the moderators and ask them to move your thread to "Building your own stompbox", then many more people will look and help. [some might even welcome you.]

something is wrong with your build. your circuit looks good, so it must be your board or assembling. please, PLEASE can we see photos of what you have built, we might spot the problem that way.
Indeed, Sir, but you asked what you could have: I can't possibly know what you would like.

antonis

Re: MXR Disto + Wampler mod DIY issue
« Reply #2 on: November 23, 2018, 10:33:38 AM »
Welcome Kortes..
[OK Stephen..??]

I should strart searching from pin3 (although something tells me you've mismatch pin voltage measurements..) going backwards..

If there isn't any short on voltage divider/bias resistor node (R2,3,4) check for shorted input cap (C2)..

Are your voltage measurements taken with ot without IC in socket..??

P.S.
No down-under prompt for IC flipping..??  :icon_eek:
« Last Edit: November 23, 2018, 10:48:09 AM by antonis »
Can't follow your signature changes, Stephen..!!
but I like what follows:
"put the coffee down, Antonis, and nobody will get hurt."
"Arggg, Jim ...."

Kortes

Re: MXR Disto + Wampler mod DIY issue
« Reply #3 on: November 23, 2018, 11:25:52 AM »
Ok sorry for the bad sitting of the post, I'll contact a moderator.

So first the pics :






Then : I measured with the op amp in place.
Yes I agree, I search primaly around pin 3, and as i search around pin 3, I discover the wrong voltage after my voltage divider.
I see no shortcut on the pcb, and I've tested with my ohmmeter, i have no buzz.
And the IC is in the good orientation.

deadastronaut

Re: MXR Disto + Wampler mod DIY issue
« Reply #4 on: November 23, 2018, 01:07:09 PM »
 3pdt  'orientation....

hard to tell from photos on the actual wiring, but first impression....
http://www.youtube.com/user/100roberthenry
https://deadastronaut.wixsite.com/effects

chasm reverb/tremshifter/faze filter/abductor II delay/timestream reverb/dreamtime delay/skinwalker hi gain dist/black triangle OD/ nano drums/space patrol fuzz//

Kortes

Re: MXR Disto + Wampler mod DIY issue
« Reply #5 on: November 23, 2018, 02:07:37 PM »
Yeah I know the 3pdt is at 90 for saving place, but is wired normally, then placed at 90.

duck_arse

Re: MXR Disto + Wampler mod DIY issue
« Reply #6 on: November 24, 2018, 08:15:45 AM »
I can't quite see what's happening on the copper side, but, from the position of those diodes relative to the IC pin 1, it is possible you have the dreaded east-west mirrored layout. it might be that you need to remove the IC from the socket, and solder it to the copper/underside of the board.

but I'm not 100% sure that is the case.

[antonis - flipping questions before photo sighting would be rude, surely.]
Indeed, Sir, but you asked what you could have: I can't possibly know what you would like.

Kortes

Re: MXR Disto + Wampler mod DIY issue
« Reply #7 on: November 25, 2018, 02:58:51 PM »
Oh I think you're right !

here the pcb from eagle :



And yes I think I have flip the negative in platesetter, what a dumb !

Just change the socket from side will be good ? Or do I have to remake the pcb ?

duck_arse

Re: MXR Disto + Wampler mod DIY issue
« Reply #8 on: November 26, 2018, 06:42:01 AM »
there is not a person here who hasn't done a board backwards, so don't worry about it. save the board as a reminder not to do it again. the simplest fix is to just solder the IC on the copper side. not much need for a socket on that side.
Indeed, Sir, but you asked what you could have: I can't possibly know what you would like.