Help - muff won't work

[KurbadsLV]

Hi, everyone. First time poster (and total electronics newbie) from Latvia here.

Hope you can help me out with this one. I finished my first stompbox a few weeks ago - a Muff Pi clone. Did everything myself, etching, painting the enclosure and so on. The result surprised me as a first time builder - everything worked as it is supposed to, the fuzzbox sounds really good. Before I plugged the fuzz in, I was almost sure I'd mess something up, but it turned out a great stoner rock-ish fuzz.

Now, the problem. Since I like fuzzes so much (and they're suitable builds for beginners, too), I decided to build another Muff Pi, this time with a mod I found online. It suggests that connecting collectors of transistors 1 and 3 will result in a loop and a "weird drone note". One should also connect the transistors through a switch to break the loop and make it a "normal" muff again. Furthermore the tutorial suggested that a photoresistor could be added to control the oscillation of the effect.

So, I basically built another Muff exactly like my first one that worked beautifully, but this time added DC power jack, another switch (1PST switch to break the loop), photoresistor and a LED to indicate the loop is engaged. Now the stompbox won't work even after I disconnected the two loop leads from transistors, so the problem shouldn't be in the modification done wrong.

I checked continuity with multimeter from jack to jack. It beeps in both switch positions (if problem is in the PCB, shouldn't it beep only when switch is in bypass position?) Checked ground - also everything seems to be connected right. I even took apart my already finished fuzz to compare the circuits. Everything seems to match. There's also 9 volts from input to output jack (also both switch positins), but basically voltage from input on PCB to output on volume pot. So - what could I have messed up? Dead components? (checked resistors and LEDs with multimeter, they do work. Unfortunately I don't have a capacitor testing and transistor testing function in my multimeter).

I also uploaded a few pics. Maybe someone can spot a mistake that I cannot: http://imgur.com/a/6vRW6
(I know, I know - very messy build, I promised myself to try and do a neater job next time )

P.S. - does above mentioned mod is a working one? Has anybody here ever done that? Also - if you have a switch with two lugs only to break or connect the loop, and you also want another LED to indicate that the loop is on, do you connect LED to switch by two separate wires and the transistor collectors by two separate wires too (so - two wires on each lug), or do you just wire LED in series after the switch?

Thanks in advance, guys (and sorry for my English, it's not my native language).

[cortezthekiller]

The input jack looks like it is wired wrong, with the tip connected to ground on the power jack.

[KurbadsLV]

Thanks for the reply, but that isn't the problem. I double checked - the tip is connected to switch as it's supposed to be. The ring goes to ground on the power jack.

[VidSicious]

Hey brolis latvis! Unfortunte that your Muff isn't working, it's very devastating.. So does it work in bypass then? Something could be touching enclosure or backofthepots and grounding out. I'm currently building a couple of muffs and I have some spare LDRs so I'll try the mod with alligator clips and let you know if it works for me. Hope you can figure out what went wrong with it!

[GiovannyS10]

Hello KurbadsLV!
Welcome to this forum!

Well, first: my english is not so good, so im sorry for it. And i make my pedals like you. I will try to help you but i need the schematic of your mod.

1. Check ALL the trails of your board.
I had some problems because the trails. Check all with your multimeter. Turn on the power and check one by one. Put a pointer on a extremity of the trail and the other multimeter pointer on the other extremity.
2. LED's resistor.
Normally i put the led's resistor on the positive of DC connector, but everyone make the things how want.

But i think i found your problem.
On this image i see a negative soldered to ring, right ? But when you connect the P10 conector there, this negative make contact with the tip.

My advice is: disconnect this negative from ring and connect it directly for the sleeve together the other negative wire. Understand? Two black wires together. And put the yellow wire on the tip. (Like your seccond jack)

Wire like this:




But if your bypass work right, this is not the problem.

Dont worry, we will help you!

One more time, welcome to the forum.

[KurbadsLV]

Thanks for the reply!

No, even the bypass didn't work. Then I re-soldered the wires on the input jack and DC power jack as you recommended. Now the bypassed signal gets through but as soon as I switch the effect on, it is dead silent - no signal. Checked every single trace on a PCB with multimeter, it beeps where it should and doesn't where it shouldn't.

(now there's one free lug - tip of the input. the ring now goes to switch. here's a pic - did I do everything right?)



But then another question arises. LED shouldn't turn on when there's no plug in the input jack to save the battery, right? Well, it does turn on now even without plug in input... On the Muff I built successfully, the one without DC power jack, only 9v battery, I soldered the input jack as I had on this one - the yellow wire goes from tip to switch, the black from ring to minus (-) lead of the battery and the other black from the sleeve to ground on circuit board. It worked then.

So, I suppose the problem lies in me being unable to wire DC input jack correctly.

As for the mod - it basically looks like this (but remember, the mod is disconnected right now, so it shouldn't be the root of the problem)


Btw, huge thanks for trying to help me out! I really appreciate it.

[KurbadsLV]

Hey brolis latvis! Unfortunte that your Muff isn't working, it's very devastating.. So does it work in bypass then? Something could be touching enclosure or backofthepots and grounding out. I'm currently building a couple of muffs and I have some spare LDRs so I'll try the mod with alligator clips and let you know if it works for me. Hope you can figure out what went wrong with it!

That'd be cool! Let us know if this mod is worth a try!

[GiovannyS10]

Hi KurbadsLV!

Okay, now you make all right, for now maintain these alterations, when we solve the problem you change again for the led only turn on when the you plug your guitar (I will teach for you how make it, you made it wrong).  I, preferentially dont like this option, my pedals turned on and off ever i want, only stomp and voilà, its works. But like is a personal thing. For now the bypass work, it is a good signal, we are on the correct way.

So, if your bypass work right, is possible the problem are on your PCB. You checked short circuit on traces? Its (the silence) seems you are grounded anything wrong, and you checked the transistors voltage? Are okay? Check the your transistors are glued okay, the pinout change with some transistors (i had problems with this before). NPN, PNP? Small transistor? Big transistor? All this influences on the pinout.  I cant see this LDR and LED on your circuit. The LDR are close to the LED? See it! Maybe the LDR are not getting a good volume of light (Few light, large resistance. So much light, very low resistance). And you checked all the resistance values on the traces? And the voltages too? Check it and show me your LDR. If you have questions, put a hard light on the LDR and try to use your pedal.

A good thing is try to wire your board only on the DC conector or only on the bat. connector. Because i cant see how you wire the DC connector and the battery connector too.

For now is all, make all and tell me the results. Questions? You can send a PM.
Good Vibes!

[KurbadsLV]

Hi KurbadsLV!

Okay, now you make all right, for now maintain these alterations, when we solve the problem you change again for the led only turn on when the you plug your guitar (I will teach for you how make it, you made it wrong).  I, preferentially dont like this option, my pedals turned on and off ever i want, only stomp and voilà, its works. But like is a personal thing. For now the bypass work, it is a good signal, we are on the correct way.

So, if your bypass work right, is possible the problem are on your PCB. You checked short circuit on traces? Its (the silence) seems you are grounded anything wrong, and you checked the transistors voltage? Are okay? Check the your transistors are glued okay, the pinout change with some transistors (i had problems with this before). NPN, PNP? Small transistor? Big transistor? All this influences on the pinout.  I cant see this LDR and LED on your circuit. The LDR are close to the LED? See it! Maybe the LDR are not getting a good volume of light (Few light, large resistance. So much light, very low resistance). And you checked all the resistance values on the traces? And the voltages too? Check it and show me your LDR. If you have questions, put a hard light on the LDR and try to use your pedal.

A good thing is try to wire your board only on the DC conector or only on the bat. connector. Because i cant see how you wire the DC connector and the battery connector too.

For now is all, make all and tell me the results. Questions? You can send a PM.
Good Vibes!

The loop/LDR modification is currently disconnected, so that should be out of consideration for now, I must get the box to work as a simple Muff first.

For including both the battery and DC jack in the build I used this guide:

How can I check if transistors are OK if I don't have a transistor testing function on my multimeter? Is there any other way? (My build uses two 2N5088 NPN and two BC549C NPN transistors). And there's basically no voltage on PCB.

For now I'll try to wire circuit only via battery or via DC jack. I'll be away for a few days, but will let you know the results as soon as I make the changes.

Thanks!

[hymenoptera]

It is possible to test transistors using the diode test setting on your multimeter. A transistor will look like two diodes back to back on the diode setting. Or two diodes face to face for PNPs. For NPN, put the red lead to the base and then try the collector or emitter using the black lead, one at a time. Base to Collector should show a diode, Base to Emitter should show a diode.

This is okay to test in-circuit in some circuits, with most BJTs, but also depends on other things in the circuit, so it's better to test them out of circuit.

[KurbadsLV]

It is possible to test transistors using the diode test setting on your multimeter. A transistor will look like two diodes back to back on the diode setting. Or two diodes face to face for PNPs. For NPN, put the red lead to the base and then try the collector or emitter using the black lead, one at a time. Base to Collector should show a diode, Base to Emitter should show a diode.

This is okay to test in-circuit in some circuits, with most BJTs, but also depends on other things in the circuit, so it's better to test them out of circuit.

Will give it a try, thanks!

[GiovannyS10]

Hymenoptera have reason, i test my transitors like this. Using the diode test. You tested the resistances?

Please, say me your progress with i say you before.

[KurbadsLV]

Hymenoptera have reason, i test my transitors like this. Using the diode test. You tested the resistances?

Please, say me your progress with i say you before.

I'm in a different city during working days, so I'll be able to work on my Muff only when friday comes. Then I'll let you know ASAP of the progress I've made!

[GiovannyS10]

Okay sir, im waiting. I continue thinking the problems are on transistors. Send me the all references for all you use, i will check they datasheet tomorrow for you.

[PRR]

> How can I check if transistors are OK if I don't....

http://www.diystompboxes.com/wiki/index.php?title=Debugging

Need schematic and voltages on transistor pins.

Working transistors will cause different voltages than dead transistors.

It is almost NEVER the transistor. #1 popular problem is solder. #2 may be wrong-value resistors, or may be backward transistor pin-order.

[Fender3D]

, or may be backward transistor pin-order.

+1
5088 and 549 have reversed pinouts

[KurbadsLV]

, or may be backward transistor pin-order.

+1
5088 and 549 have reversed pinouts

Allright, this could be it! I used different type of transistors than the shematic suggested (looked them up in a forum for Muff mods), and two differend pairs. Did this also in my first muff, which works (but I'm not sure which transistors I used then, will be able to check this during weekend).

So, if they have reversed pinouts (never thought of it), then one pair is installed the other way around. Will definetely reinstall them and let you know if this was the cause of the problem.

Thanks.

[KurbadsLV]

Ok, I got it to work as a normal muff (sort of... it doesn't sound as tight and gainy as the first one I made. Probably the effect of different transistors and diodes used - I gave a germanium pair a shot in second clipping stage).

It looks like the problem was in the two of the transistors installed wrong. Reinstalled the BC549C's the other way around, then wired it up via 9v battery only, and it worked. Then added DC jack - so far, so good. Diode will light up only when plug is inserted, Muff still works.

Then I tried to add the mod I've been talking about. It fell silent again - works in a true bypass mode only. If I engage the second switch (to activate the loop), Muff only gives out a strange, silent wailing sound, but it ain't the signal from the guitar, because nothing changes in the signal as I strum the strings. It changes pitch when I put my hand in front of LDR included in the loop. The second LED won't light up either.

Any recommendations? As I mentioned earlier, the mod is as follows:

"Feedback mod: This mod is also not for anyone. It will give the Muff a weird drone note that will interact with the notes played resulting in octaves (up and down), nintendo sounds or a huge MUSH. Can sound quite nice and interesting!!!!! The mod is done with a feedback loop: connecting two points together and letting signal flow back. I found two of these loops in my Muff (note: more can be there; try for yourself!)

   1.
      Connect the emitter of Q3 with the emitter of Q2 through a switch (so you can turn the loop off). The sustain will be on full when this mod is engaged.
   2.
      Connect the collector of Q3 with the collector of Q1 through a switch. The sustain now can be varied by the sustain knob.

A nice control of this feedback loop can be made by inserting a LDR (Light Dependent Resistor) between the two points. This way the amount of light will determine the amount of current going through the feedback loop."

Only now I'm confused -is the LDR supposed to go where original tone knob is or should it go between the wires connecting Q1 and Q3?
Also - I need this to be engaged or disengaged via the footswitch + the LED indicating the mod is on.

Currently my idea goes like this (sorry for the amateurish visualisation, I'm yet to discover the world of schematic drawing software).
It probably ain't right way to wire this mod, so I'm asking for your advice.




Btw, thanks, guys, for all your comments! Without your help the stompbox would still be silent as a grave.

[hymenoptera]

Pretty sure the middle pin on those transistors is the BASE. Check your pinouts again, and confirm against a schematic.

Here's one, not sure what version though
http://www.kitrae.net/music/Images_Secret_Music_Page/BIG%20MUFF%20CIRCUIT%20GUIDEsm.jpg

[KurbadsLV]

Ok, got the feedback loop and LDR working through second footswitch also! The only thing now left that's not working is a second LED to indicate feedback loop is on. How should i wire it?

The mod circuit now goes like this: wire from collector of Q1 -> first lug of the switch -> second lug of the switch -> first lead of LDR -> second lead of LDR -> wire to collector of Q3.

Where the LED should go? I tried several versions, none of them worked. The LED itself is ok, I checked it with multimeter.