Big Muff Pi

[Neve1073lover]

Latest Project. Fuzzzzzzzz
Design from generalguitargadgets.com.
Doing the 70's version:

Son yet to have time to do anything but University so yet to test.
Need to add the LED (the spare wire...)

 

[Neve1073lover]

Don't Trust Power Packs!!!!

Found a 9V power pack with the correct plug size and with the centre positive.

Ran it up and working OK (fender Strat through JTM clone to 4x12).

Went POP.

Tested power pack and showing 12.5V.

Will now look for popped parts (probably a transistor). Cannot see anything just by looking.

 

[mshilarious]

Found a 9V power pack with the correct plug size and with the centre positive.

Ran it up and working OK (fender Strat through JTM clone to 4x12).

Went POP.

Tested power pack and showing 12.5V.

Will now look for popped parts (probably a transistor). Cannot see anything just by looking.

That's very typical for an unloaded supply, in fact they can even be a few volts higher than that. It should drop closer to rated voltage when the load is close to the power supply rating. Anyway, a circuit should incorporate some sort of regulation or at least protection against overvoltage if you are using an external power supply.

That said, I can't imagine a part that can tolerate 9V but not 12V

 

[Dr ZEE]

... I can't imagine a part that can tolerate 9V but not 12V

Good point. Me neither. Unless the circuit is an "overly creative" one, and I mean really! overly
Mr. Neve, seriously, it would be cool if you drop a note about what exactly happened there after your investigation.
Also, The Pi-pedal work looks cool Which transistors did you use there exactly?

 

[mshilarious]

Good point. Me neither. Unless the circuit is an "overly creative" one, and I mean really! overly
Mr. Neve, seriously, it would be cool if you drop a note about what exactly happened there after your investigation.
Also, The Pi-pedal work looks cool Which transistors did you use there exactly?

I mean there are plenty of digital parts that will pop at +9V . . . that's because they are designed for +5V!

Discrete transistors can usually manage at least +20V, you almost have to purposely pick a part that tolerates less . . . so I'm guessing there was some component that maybe got too much current or power dissipation as a result of the overvoltage. Still, that's running parts really close to their limits.

A 9V zener protected by a 47 ohm 1W resistor or something isn't a terrible idea across the external power input. Or if that is too little current, use the zener at the base of a power transistor, across a 10K resistor. Filter caps are nice!

Maybe an appropriate fuse too . . .

 

[Neve1073lover]

Good point. Me neither. Unless the circuit is an "overly creative" one, and I mean really! overly
Mr. Neve, seriously, it would be cool if you drop a note about what exactly happened there after your investigation.
Also, The Pi-pedal work looks cool Which transistors did you use there exactly?

I used 2N3904 as I could source them easily.
Not sure I actually have a problem yet. I also did not think 12V would be a problem, that's why I went ahead.
I will post my problem when I find it.
I built it totally from scratch and cost me $65AUS. I did already have some pcb blank and etchant.
I attached the pcb to the case top with two layers of double sided thin foam tape. Worked out very nicely but a PITA to now take off if I need to.
I routed the wires as pictured to allow me to easily access the insides.
Before I shrink wrapped the wires, I put small lengths of red shrink wrap on each wire and marked it with lines to denote 1, 2, 3 etc. (ie one mark on wrap for '1', two marks for '2' etc). A smart way to keep track of your wires.

Also the BOM says you need a Heavy Duty 3PDT foot switch. Really only need a DPDT.
Garry

 

[Dr ZEE]

... some component that maybe got too much current or power dissipation as a result of the overvoltage . .

In the 'situation as described' 'too high current' would sure "fix" the "overvoltage" problem and thus would "self regulate" ..heh heh
I had to use " quotes" " " a lot
Unless I really don't know something I don't see anything on the circuit board as pictured that could be blown by 12VDC, given this IS Pi Big Muff circuit

 

[Dr ZEE]

I used 2N3904 as I could source them easily.
Not sure I actually have a problem yet. I also did not think 12V would be a problem, that's why I went ahead.
I will post my problem when I find it.
I built it totally from scratch and cost me $65AUS. I did already have some pcb blank and etchant.
I attached the pcb to the case top with two layers of double sided thin foam tape. Worked out very nicely but a PITA to now take off if I need to.
I routed the wires as pictured to allow me to easily access the insides.
Before I shrink wrapped the wires, I put small lengths of red shrink wrap on each wire and marked it with lines to denote 1, 2, 3 etc. (ie one mark on wrap for '1', two marks for '2' etc). A smart way to keep track of your wires.
Garry

Yeah, Garry, drop a note if you figure the exact "problem" or what ever is going on there. To avoid guessing and confusions. I think if everything cool with your circuit it should work ok with power pack you have. Well, maybe I'm missing something. Good luck.

btw, 2N3904 is a fine device

 

[Neve1073lover]

Yeah, Garry, drop a note if you figure the exact "problem" or what ever is going on there. To avoid guessing and confusions. I think if everything cool with your circuit it should work ok with power pack you have. Well, maybe I'm missing something. Good luck.

btw, 2N3904 is a fine device

The photo DOES actually have a wiring error I picked up later....(How I wired the DPDT).
During my test it worked as a pass through etc properly.
Should be simple to find the problem. I will hang a signal generator and CRO off it tonight if I have time.
My initial testing was going fine but we needed to crank up the JMP45 too much to test it properly.

 

[mshilarious]

Also the BOM says you need a Heavy Duty 3PDT foot switch. Really only need a DPDT.
Garry

Guitar pedal makers love both their true bypass and their power on LEDs. Skip one or the other, and you don't need 3PDT.

 

[Neve1073lover]

No Problem Other Than Pot Wiring

I had the Sustain and Vol wiring back-the-front.

The Pot connections are numbered 1, 2 and 3 when you are looking from behind and with the connections UP.

Vol Connection 1 goes to Earth, 2 to DPDT and 3 to the 'C' point on the board that is right at the 0.1 uF Cap.

The Board Sustain connections (S1, S2 and S3) are correctly labeled.

Pots then correctly work in the clockwise direction to increase Vol or Sustain......

Tested with the Power pack I had. Also found that the power pack connection to the pedal was not very reliable. This probably was my real problem.

 

[Neve1073lover]

Sounds Great

Son demoed it to me and it sounds terrific.

Wish I could talk him into doing some recordings though...

This pedal was so much fun I may make another one.

What type though? Any suggestions (already have a tube screamer).

 

[Dr ZEE]

...

What type though? Any suggestions

Something with no "name" yet. "CREATE" something

 

[Neve1073lover]

Something with no "name" yet.

Unfortunately my electronics experience cannot hold a candle to yours Dr ZEE. I have checked out your web site and see that you are obviously an expert in the field of audio electronics.

I just enjoy the thrill of doing something new (eg UV pcbs).

My son loves the early guitar sounds and that is why I am into projects with a 'name'.

I am merely trying to help out the beginners like me and document my successes, failures and what worked.

 

[Dr ZEE]

Huh huh, Garry, we all are "experts" here, all right
Get yourself a breadboard and a bag of electronic junk and start stiking thing in it, read something in between sticking sessions, you'll be an expert before you know it