ggg big muff problem

[oliphaunt]

i'm getting signal out of c1 over to q1, where i only seem to be getting signal from the collector and base... is it supposed to do that?

Yes it is supposed to do that.  The Emitter of Q1 is connected to ground and so any audio signal that might be there will be shorted out.  The audio signal at the base should be pretty much the same as you are hearing at the beginning of the chain.  The signal at the collector should be louder, but still clean and undistorted.   You might hear some rolloff of the high end due to the filter cap in the feedback loop.  Now check for sound at C3 and C4.  With the sustain pot all the way up the signal should be pretty much the same volume as what you hear at the Q1 collector.  At the Q2 base if all is correct you will hear the signal get quieter, and become somewhat distorted and maube a little more loss of high end.  The collector of Q2 will also sound distorted and be louder than the base.  The same thing happens at Q3, but it gets even more distorted.   

Let's see how you are doing so far...

I understand your frustration.  For a beginner (I'm only a little ahead of you) the Big Muff is a large project.  There are still some basic concepts that you need to get under control so that you can anticipate how the circuit should act at various points.  This familiarity really helps when debugging.  You may find that you can benefit by putting the Muff down and building a boost or two, and a simple overdrive like the Electra, first on a breadboard then finishing them on stripboard or perfboard.  Once you've done that the basic building blocks are in place and the Muff isn't so overwhelming, it's just mulitiple stages of familiar concepts.

[olslick]

so i completely re-did all the wiring. i replaced the 4 transisters with 5088s, replaced r1, r3, c1, c2 and c3 all with no results. it's still doing the same thing it was when i first put it together. as of right now c15 and r26 are gone and c11 and c13 are aluminum electrolytic. i didn't have a spare for c2, so i used the violet ram's head cap there. i don't know what to do. there's no solder bridges, and i've gone back touching things up to make sure there wasn't a cold joint. i can't see any cracks in the pcb. i really don't know what to do.

[olslick]

alright, i need some help here. i re-did the whole thing and it still didn't work. i told jd at ggg and he was kind enough to send me a new board, and guess what? it's doing the same thing. now i feel totally awful and embarrassed. i don't know what to do. if it's still doing the same thing, it shouldn't be because of a bad joint or wire or solder bridge. there has to be some simple explanation for this that i'm not seeing. according to reference pics i found at ggg and a pic oliphaunt posted some time ago, everything is oriented correctly. i've checked my wiring and values each ten times, and everything looks right.

the only resistor i'm not sure of is r4, because 120 ohm looks so similar to 10k. i'm fairly certain that's not the case but could that cause the trouble i'm experiencing? the last time i went to plug it in it shocked me pretty good, maybe this is some grounding issue? the effect is in an old, green russian muff box i found. in order to fit the components in the larger holes it had, i had to use metal washers. could this have created some sort of ground short? mind you, there's nothing in the pcb pad marked "g". should i install a ground there and connect it to the enclosure?

i hate to seem bothersome and easily frustrated, but i've been working on this for quite a while with no results. i do believe that when this problem is resolved, i'll be a smarter and more confident builder for the experience, but i am super bummed. in addition to the extra time and money i've personally spent to do this over and over, i've taken up people's time here and jd even sent me a new board. while i'm extemely grateful he did that, i'm pretty embarrassed as it seems as though the board wasn't the initial problem.

i really would appreciate if some of the more experienced builders here could look over everything i've done and point out whatever dumb thing i'm missing and i promise one day i'll do the same for some other noob.

[olslick]

okay, so just to re-cap... when the effect is bypassed, the signal is fine. when i engage the effect, i get nothing. unless i turn the pots up all the way in which you can hear a very faint distorted guitar signal and white noise. i do have a 3pdt and everything has been re-soldered with new components and a new pcb, with the exception of the switch, the jacks and the pots everything is new. though i did rewire all of those components just in case there was a faulty wire or a bad connection. the effect is currently wired up inside the green muff enclosure.

i do have a multimeter, but i'm not very good at using it. i tried measuring the resistors and did, well i don't know how to measure the resistors. i put the black needle on the ground, and the red needle on either lead of the resistor and nothing. i put both needles on the leads of the resistor and still nothing. i would get readings but mostly inconsistent gibberish on all the various resistor settings. the only resistor i wasn't sure on is the 120 ohm at r4, as it's color bands are so similar to a 10k.

as far as emulating the ground connection on the output jack, i'm assuming that's the wire that connects the jacks together at the sleeve, then goes to the ground on the board? if that's correct, then i have done that.

will post more pics later.

[Hupla]

Im not great at debugging but from your voltage levels it looks like the Q1 transistor isn't turning on. Change that if you can and see if that makes a difference. of course if your audio probe shows that the signal is going past Q1 then it might'nt be the problem but give it a go anyway.

[olslick]

 yeah, it's not the transistor itself. i've built it now on two different boards with three different sets of transistors. that could be the problem, but something else would have to be causing it. has anyone ever had to change anything when building one of these?

i hate to continue looking outward to solve this, but ggg just sent me an envelope today that had two resistors in it for a micro-amp kit i ordered. i haven't started building it yet as i wanted to finish this first, but they claim that they sent me two resistors that were wrong. i had no idea. then there's the foxx tone machine bill of materials that lists c11, a 0.047uf cap as being film. being a noob, i didn't notice those numbers and tried to find this thing. eventually ggg responded to an email i sent them asking about it, informing me of the typo.

i'm not putting the blame on ggg by any means, they've been completely awesome with me to say the least. for both of these instances, had i been more experienced, i would have spotted these mistakes a lot earlier on. i'm sure whatever is causing this ram's head muff not to work is no different.

the thing that's got me so down is that i don't understand what could be so wrong with this pedal-by-numbers business. yeah, had i tried to build something from scratch, okay. but i bought the kit, you know? i'm pretty new to this, but not completely. i've built three octavia clone pedals and done lots of little mods to things here and there. never had problems before. it's all just following the instructions, right?

[olslick]

oliphaunt, upon closer inspection i notice that your ram's head doesn't at all follow the wiring diagram as shown on the ggg site. you also didn't connect the input/output with the ground wire. c4 and c10 look as though they've been swapped, though i just assumed that was a tone changing decision. could you explain these differences to me? is this just because you didn't hook up a battery jack, so you didn't need a stereo input?

here's oliphaunt's ram's head  http://www.diystompboxes.com/smfforum/index.php?action=profile;u=21045;sa=showPosts;start=80

here's the ggg site generic muff wiring diagram http://www.generalguitargadgets.com/pdf/ggg_bmp_wiring.pdf

[oliphaunt]

oliphaunt, upon closer inspection i notice that your ram's head doesn't at all follow the wiring diagram as shown on the ggg site. you also didn't connect the input/output with the ground wire. c4 and c10 look as though they've been swapped, though i just assumed that was a tone changing decision. could you explain these differences to me? is this just because you didn't hook up a battery jack, so you didn't need a stereo input?

here's oliphaunt's ram's head  http://www.diystompboxes.com/smfforum/index.php?action=profile;u=21045;sa=showPosts;start=80

here's the ggg site generic muff wiring diagram http://www.generalguitargadgets.com/pdf/ggg_bmp_wiring.pdf

Here is the pic:


I did not use a battery so that is a deviation from the GGG wiring diagram.  I do not need a stereo jack as a result.  The hot and ground from the 9V power supply jack are connected directly to the circuit board and I connected all other grounds using wires from the four extra ground connections on the circuit board, as well as the +9V output to the LED.  The input jack does have a green ground connection wire, but the output jack does not.  It is grounded through the physical connection to the metal enclosure which is grounded since it is in contact with the grounded input jack.

C4 and C10 are the GGG values for a Ram's Head, I did not make a change there.

I omitted C15 and C2.  C15 is a power filtering cap if I recall, and I didn't seem to need it.  I breadboarded this circuit first and didn't have that  cap on the schematic I was working from, so I left it off.  C2 I left out as a tonal choice.  It filters out high end, and I prefer the sound with that little bit of top end left in there.  I put a socket there though so I can change my mind or easily experiment with other cap values.

I wish I had more to offer you, but there are some basic debugging skills it seems you are missing.  It just takes time and experience with simpler circuits to be able to predict where signal should be present and where it should not so that you can make good use of an audio probe.  Also things like being able to use your DMM to get measurements is vital.  Again, I suggest you build a boost or a buffer, or simple OD circuit like the Electra on a breadboard and really play with it and figure out what is going on.  The Big Muff is a combination of several simple circuits and it becomes fairly easy to understand what is wrong with it if you know what each section is doing.  It took me about 6 months of DYIingf rom scratch builds, not kits or "electronics by numbers" before I looked at a BM schematic one day and thought to myself, "oh, I get it".

All that said, use your audio probe and touch it to the base of Q1 (the lead in the middle of the transistor with the circuit board oriented with the text at the bottom).   If you hear clean clear guitar signal then touch the emitter ( the lead on the right).  It should sound the same but louder.   If this is the case move on to the next transistor.  You will hear distortion at this point, but again the base will be quiet, the emitter will be louder, and so on.  When something doesn't sound right let us know and we'll go from there...

[Smoky Barnable]

I just finished the ggg big muff kit today. This was my first build and I wouldn't presume to offer any advice. What I can say is it didn't work at first but I figured out I had a cold joint at the Q1 transistor that revealed itself by a voltage check. I checked all my other connections with a magnifying glass and found a few other suspect joints. Make sure your r4 resistor isn't 10k. Can you take a close up pic of your pcb and switch? Could it be a wiring problem with your switch?

[mmaatt25]

Hi,

I built a GGG BM triangle version recently and had no trouble at all, worked first time. I built this after trying to build one using the Torchy stripboard layout without success. One thing I did learn through that process is the blocking effect of electrolytic caps, if there the wrong way round they block the signal, my be worth double checking.

Are the transistor voltages you posted originally still the same? If they are Q1 isn't right.

Oliphaunt's advice in his last post is spot on, audio probe from Q1 through, follow the signal Q1 clean boost, Q2 & Q3 distortion, both have clipping stages and Q4 boosts the final signal.

There is post on this site, that gave a break down of every component on the big muff circuit, various people added posts explaining each part. It's definitely worth reading.

Matt

[Jarno]

I built two using the Tonepad layout, one with silicon transistors and one with germanium ones. Both worked fine on first startup, but I did have to do some swapping of biasing resistors to get them juuusst right (even though I did use the big muff resistor calculator tool).
Big Muff Bias Resistors Calculator

[petemoore]

  Figure out which transistor isn't working.
  Use the DMM to find off-bias voltages, or the audio probe to find out if the collector signal is an amplified version of the base signal.
  Then use the DMM to find where to correct, er, what's wrong.
  Set for R, measure every resistor value [compare to schematic].
  Set for "Beep" measure every connection, include transistor pins.
  Set for ''beep'' measure every non-connection.
  Every once in a while I never got a bad capacitor or transistor, it's possible I suppose, but since they can't be measured other than:
  Measuring that the capacitors doesn't conduct DC [haven't found this test particularly useful, none have done that yet].
  Measureing that the transistor diodes are intact, some DMM's have a socket for Hfe measurement, also a good indicator of transistor goodness.
  Take small portions of the schematic and board, load them in your skullputer, these small boards are packed in tight, the linear formula of schematic folds, twists and turns by the time it can be placed in physical form on a tidy board.

[ringworm]

I built two using the Tonepad layout, one with silicon transistors and one with germanium ones. Both worked fine on first startup, but I did have to do some swapping of biasing resistors to get them juuusst right (even though I did use the big muff resistor calculator tool).
Big Muff Bias Resistors Calculator

Don't mean to take this off track but... how would I use this calculator?

[Jarno]

You measure or put in the Hfe and leakage of the transistor you're going to use and try a number of values for the resistors, to get the Vc to about 4-5 volts.

[ringworm]

Hijacking now...
What is Vbe and how do I measure it?
Would I bias each of the three stages before the final boost stage or just the first sustain stage?

[Jarno]

I think I did all of them, but there is plenty of info around. Also on "the other" forum.

[olslick]

 IT IS FIXED.

thank you everyone for your help and advice. the problem was a wrong resistor. i went through with the audio-probe and couldn't get sound from the collector of q1 and the sound at the base was very quiet. so i replaced all the resistors that connect to q1 and it worked. i'm very relieved that it's over but also bummed because it was a stupid problem that i refused to see. i was so sure that the color codes were right. i couldn't read them with the ohm-meter because the effect wasn't plugged in, by the way.  go figure i didn't know that's how that works. people swap resistors all the time, i couldn't believe that could be the cause of the effect not working at all.

well i could ramble on all night about how dense i am, but i've wasted enough of your time for now. thank you very much for everyone who offered help. i owe you.

very humble,
ben

[oliphaunt]

Congrats!

Just a thought, when you try to measure a resistor that is soldered onto a circuit board you are measuring not just the value of the resistor but also anything it may be connected to.  As a result you may not get the value of the resistor by itself.  You have to look at the schematic and figure out what path things are taking and what the total expected resistance should be.  This is independent of the circuit being powered or not.