MXR Distortion Plus clone - It works and then it quits

[jcwillow777]

I just built the MXR Distortion Plus: http://tonepad.com/project.asp?id=2

I am having some problems which are listed below.

1.What does it do, not do, and sound like?

It will works great for about 45 seconds and then it stops. Sometimes it fades out and sometimes it just stops. If I let the pedal cool down for a few hours and try it again it will fire up, but then it quits again after about 45 seconds. After I got it running I decided to try some different chips, I installed a socket. None that I put in worked, so I went back to the 741 that it called for. I did buy two 741s. I tried both and it did the same.

2.Name of the circuit = MXR Distortion Plus

3.Source of the circuit (URL of schematic or project) = I bought the circuit board.

http://tonepad.com/project.asp?id=2
http://tonepad.com/getFileInfo.asp?id=115

4.Any modifications to the circuit? Not sure if this is a modification. I used a mono jack for the input and output. I don't like using a battery, only a 9 volt power supply. I used a 3PDT switch.

5.Any parts substitutions? Yes. It calls for a 10pf cap in C5. I didn't have one so I used a 47pf.

6.Positive ground to negative ground conversion? Not sure, I wired it up as the layout shows. my guess is no.

7.Turn your meter on, set it to the 10V or 20V scale. Remove the battery from the battery clip. Probe the battery terminals with the meter leads before putting it in the clip. What is the out of circuit battery voltage? =>

Neg - 0

Pos - The readings vary, when I take the probe of it does the same thing.


I'm not using a battery. I am using a 9 volt power supply.

Now insert the battery into the clip. If your effect is wired so that a plug must be in the input or output jack to turn the battery power on, insert one end of a cord into that jack. Connect the negative/black meter lead to signal ground by clipping the negative/black lead to the outer sleeve of the input or output jack, whichever does not have a plug in it. With the negative lead on signal ground, measure the following:

Voltage at the circuit board end of the red battery lead = 8.85 volts

Voltage at the circuit board end of the black battery lead = 0

Now, using the original schematic as a reference for which part is which (that is, which transistor is Q1, Q2, etc. and which IC is IC1, IC2, C1, and so on) measure and list the voltage on each pin of every transistor and IC. Just keep the black lead on ground, and touch the pointed end of the red probe to each one in turn. Report the voltages as follows:

Q1-  Doesn't have any transistors

IC1 (or U1)
P1 - 0
P2 - 1.867V
P3 - 0
P3 - 0
P4 - 1.886V
P5 - 0
P6 - 1.886V
P7 - 8.85V
P8 - gradually going up. When I took the probe off the MM it did the same thing when the positive probe wasn't on anything.


D1
A (anode, the non-band end) = 0
K (cathode, the banded end) = 0

D2
A = 0
K = 0

Thanks for your help

[Mark Hammer]

If you are using an external supply, and the circuit craps out after a predictable amount of time, the obvious question is whether the same supply craps out with other effects in a similar fashion (if not the identical amount of time).

I ask because it is always possible that the issue is not with the pedal but with the supply.  Do yourself a favour and try it out with a 9v battery.  If you don't have any battery snaps handy, use a dead battery and make one: http://hammer.ampage.org/files/DIY-snaps.pdf

[jaki54321]

ive had an issue like this before. not with the same pedal but power. try a 9v battery, if u dont have a 9v battery clip ill give u a pic that will show how.

edut: btw i looked at the part list for the distortion+, it says nothing for c5, are u sure u didnt mean c6? and i would buy a 10pf cap if the power supply isnt the issue

[jcwillow777]

Thanks guys.

Okay, I tried a couple of different power supplies and the same thing. I tried these same power supplies with another pedal and it worked fine.

So, I pulled all the connections off the board and went with a DPDT switch, stereo input jack and a 9 volt battery and rewired it. Same thing. Once in a while sound would come through, but most of the time it is either crackling or nothing. Is it possible that one of the different chips I tried out fried something on the board?

These are the chips I tried:

TL072ACN, TL082ACN, RC4558P, RC4559P, TSH221N, LM833N, NE5532AP, OP2604AP (I don't think I got sound from the pedal with any of them)

I'm gonna quit for the night, I'll try again in the morning.
Thanks again.

[Fender3D]

If you bought the "MAS Distortion" board, it's designed for 741 op amp.
No TL0x2 double op amps then.

[jcwillow777]

If you bought the "MAS Distortion" board, it's designed for 741 op amp.
No TL0x2 double op amps then.

Thanks Fender.

Yeah, that's the board I bought. So, could I have fried something on the board by plugging in some of these other chips? I can't remember for sure how long I played the pedal after I finished it, but I was playing the pedal for a while, without trying any other chips, and it worked fine.

[Fender3D]

You should have fried just the op amp.
Unless you placed any tantalum... those s***ers broke each friday...

[jcwillow777]

Okay, I got it going, using a battery and DPDT. I went over all of my solder joints again. There were a couple that looked really close, like the solder might have been touching. I inspected the joints with a magnifying glass and though they looked like they might be okay I redid them again. That must have been the problem. I'm gonna order a case to put it in. I have a couple of cases from other pedals I built a few years ago that I will never use, so it is in there for now. When I get the case I'll hook up the 3PDT switch again and LED.

Thanks to everyone for your help.

[jaki54321]

Okay, I got it going, using a battery and DPDT. I went over all of my solder joints again. There were a couple that looked really close, like the solder might have been touching. I inspected the joints with a magnifying glass and though they looked like they might be okay I redid them again. That must have been the problem. I'm gonna order a case to put it in. I have a couple of cases from other pedals I built a few years ago that I will never use, so it is in there for now. When I get the case I'll hook up the 3PDT switch again and LED.

Thanks to everyone for your help.

Also about the op amp. If you did put in the wrong Op amp for the circuit, you may have fried the chip or damaged it, not the board. Fender3D is right. So if this problem still persist with a different op amp, try the normal one. Idk where you buy your parts but they have it at small bear:

http://www.smallbearelec.com/Detail.bok?no=209

also use an IC socket if you are not using one(Im sure you are tho) they really help in reliability.

Good luck! 

[jcwillow777]

Thanks. I'm using a socket. I learned that trick several years ago when I first started messing around with pedals (Brian Wampler). I got my chip from smallbear too. In fact, I bought 2 just in case...

I put the pedal together using a DPDT that I took out of a Morley wah I had, the switch was noisy so I replaced it, but I figured it would work for this. So, it was playing descent, no problems except when I quit playing there was a weird swirling pink noise. So I hook up the put the 3PDT, with LED and 9V plug, thinking it was the switch and I'm back to square one again. It works for 30 seconds and quits. I still get the swirling noise when not playing. I don't remember that before this all started. I wired my 3PDT switch like shown here, Aaron's diagram. I got the diagram a few years ago and I haven't had any problems with it. Toneworks shows a different diagram of wiring it up, which I think I'll try, but not today or even this weekend. I have too much stuff going on, maybe I'll try again next week. I'm really hoping I can use a 9V plug, I hate messing around with batteries. I'm always forgetting to unplug and then the battery is dead the next time I want to use it.

I really appreciate everyone's feedback. Thanks!

[jaki54321]

Thanks. I'm using a socket. I learned that trick several years ago when I first started messing around with pedals (Brian Wampler). I got my chip from smallbear too. In fact, I bought 2 just in case...

I put the pedal together using a DPDT that I took out of a Morley wah I had, the switch was noisy so I replaced it, but I figured it would work for this. So, it was playing descent, no problems except when I quit playing there was a weird swirling pink noise. So I hook up the put the 3PDT, with LED and 9V plug, thinking it was the switch and I'm back to square one again. It works for 30 seconds and quits. I still get the swirling noise when not playing. I don't remember that before this all started. I wired my 3PDT switch like shown here, Aaron's diagram. I got the diagram a few years ago and I haven't had any problems with it. Toneworks shows a different diagram of wiring it up, which I think I'll try, but not today or even this weekend. I have too much stuff going on, maybe I'll try again next week. I'm really hoping I can use a 9V plug, I hate messing around with batteries. I'm always forgetting to unplug and then the battery is dead the next time I want to use it.

I really appreciate everyone's feedback. Thanks!

No problem. It could be possible that the wall wart is not regulated. Which is normal... Are you using a wall wart(DC adapter that plugs into the wall?) Try a 9V battery(I know you dont like too but jus give it a shot for a test) and see if that sound continues, if it clears up with the battery, try this:

I am still trying to do this for my own pedal because im running at 18V but since ur running at 9, this might work. Take an Electrolytic Capacitor, i recommend at least 100uF, maybe 500uF but 100 would work ok too, id try 500 but no more then tat, but thats just me. Take it and connect the positive leg on the cap to the positive rail on the jack inside the pedal. if u cant put it right on the jack you can use wires to connect it from another position. then connect the Negative Leg to the Negative Rail on the DC jack. It may help filter out the power.

If that still doesnt work, try to build a Huminator Pedal from Beavis Audio. Its a very simple inexpensive build. What you do is you plug in your Power supply unit to one side of it and connect a cable from the other side to your pedal, the electronics inside may filter out the Power and will kill the noise you are hearing.

I am not 100 percent sure if these will work, but its worth a shot. It will not damage your pedal or anything. Also if you have an extra elecrolytic cap laying around, no matter the value, u could try it. Even if it is smaller the 100uF, if its all u have, its worth a shot. Im no professional, as I jus learned this from my friends here on this forum, but it has been known to work well.

Good luck