Shin-Ei Fuzz clone build (GGG kit) - sounded great, then out of the blue..?

[cactus friend]

Hi All,

I recently built a Shin-Ei Companion Fuzz, from the GGG kit.  It sounded great and worked perfectly upon using it:

Link to YouTube video of me 'demoing' it

But then, at some point (not while playing), i went to use it again and it sounded very muddy/dark compared to the bypassed tone, and barely 'broke up/clipped' at all.  I tried four different batteries in various states of charge...eventually all fully-charged rechargeable batteries (both 8.4v and 9.6v), only to get the same effect.  Adjusting the volume pot had some effect, adjusting the fuzz pot had little to none.

Then, I did a reading of the pins on each of the transistors using the build guide on GGG.com.  Everything checked out EXCEPT for the Collector pin of Q2, which was more like 0.2-0.3v instead of 2.0v.  I checked the leads and joints leading to/from it and resoldered a bunch of them even though they seemed fine.  Still, the same problem.

I'm starting to suspect that the actual transistor used for Q2 somehow got fried.  I'm going to try using a wall wart power supply to see if it has to do with rechargeable 9v batteries or something.  

Does anyone have any experience with this build/problem?  Thanks!!

Edit: from the kit, no substitutions, all of the readings of each pin of each transistor were spot-on except for the one mentioned, and as far as transistor orientation I triple-checked everything (two transistors were of the metal-topped-with-tab sort, the third was the more typical black with one flat side sort), and since it used to work fine as exampled in the video...I think the orientation of each is okay.

[glops]

Search Shin-Ei Companion FY2 on this forum.  There's tons of threads.  Mark Hammer posted in one of the threads voltage readings taken from an original unit.  Your collector voltage on Q2 looks too low.  Maybe make sure the collector resistor is still connected to 9V.  Recheck all the other junctions around Q2, as well...

[cactus friend]

Thanks, I've been reading the other threads on it...seems like biasing Q2 can be an issue...?  Everything seems to be soldered properly; I'll double check that the resistor is still connected to 9v...from what I remember it was getting around 3v or so...

[drewl]

What transistors are you guys using for these?

I was messing around with one I built a couple years ago....it's got run of the mill 3904 or 3906's in it and never sounded good which is why I never really use it....I had put a pot in there to bias Q2.

[glops]

Yeah, your bias on Q2's collector is too low.  I think it's supposed to be closer to .8, .9 and upwards from that.  What are the voltages on B and E on Q2.  Also double check that the wire from Q3 going to the fuzz pot hasn't snapped off the pot or PCB.  I think the original Q2 voltage is closer to 1 volt and not the 2 volts per the GGG doc. To my ears it always sounded better closer to 1 volt

Drewl,  I tried 3904's a couple of years ago and they sounded like crap to me.  Made the pedal sound really like the bias was way off.  I had an assortment  of various other silicons that I got better results with than 3904s.  Too blatty and splatty.  Try different trannies in the 200-00 hfe range.  I tried lots of different ones and had different results.

[LucifersTrip]

What transistors are you guys using for these?

I just used the one the schematic called for [2SC536] and it sounded great. They are easy to get.

The GGG build instructions mention C536F7G, so the 2SC536 is probably a good choice.

Sub 50k/100K pots for the 10k/15K resistors in the scoop and really have some fun....

[LucifersTrip]

Then, I did a reading of the pins on each of the transistors using the build guide on GGG.com.  Everything checked out EXCEPT for the Collector pin of Q2, which was more like 0.2-0.3v instead of 2.0v.  I checked the leads and joints leading to/from it and resoldered a bunch of them even though they seemed fine.  Still, the same problem.

Is it possible that the the voltages of the transistor in the third boost stage (Q3) be correct if one of the voltages of the previous stage (Q2) is wrong? I would double check the voltages on Q3.

This may also be a job for the audio probe:
http://www.diyguitarist.com/PDF_Files/DIY-AudioTester.pdf

Can you easily pull Q2 and measure the gain?

It is very possible that components not directly surrounding Q2 could cause the problem, so only checking solder connections around Q2 may not be enough.

Sounds like you either blew a component or a connection went bad.

[cactus friend]

Thanks for the link to that audio tester probe!  That'll definitely be a useful tool to have.  I'm starting to think a small practice amp might be a good idea, too...so that my neighbors don't call the cops.

Sounds like you either blew a component or a connection went bad.

That's what I think, too.  The solder joints are all very tight and secure, and the pedal worked fine before.  It was even 'wiggle test' proof.  I'll try to replace Q2 and hope that it wasn't something else in the circuit that messed it up in the first place...

[cactus friend]

Replacing Q2 with a new one fixed it!

Thanks for taking a look.

[bigmufffuzzwizz]

I just used the one the schematic called for [2SC536] and it sounded great. They are easy to get.

The GGG build instructions mention C536F7G, so the 2SC536 is probably a good choice.

Sub 50k/100K pots for the 10k/15K resistors in the scoop and really have some fun....

Just found those transistors and they cheap!! 
Definitely wanna give your pot substitution idea a try. Im just not sure how I would add into the circuit. Would lugs 3-2 or 2-1 be connected and then lugs 1 and 3 go in place of the resistors? I would like to learn the theory behind this..

[cactus friend]

Just found those transistors and they cheap!! 
Definitely wanna give your pot substitution idea a try. Im just not sure how I would add into the circuit. Would lugs 3-2 or 2-1 be connected and then lugs 1 and 3 go in place of the resistors? I would like to learn the theory behind this..

Think of a pot as like a variable resistor, with the middle pin attached to the 'divider' that sweeps along as you turn it.  So, say you have a 100k pot, if it's turned exactly half way, you'll have 50k resistance between pins 1 and 2, and 50k resistance between pins 2 and 3, as it's divided in half.  So in essence, you really only need to use two pins, though it might be a good idea to tie two of them together or ground the third one.  I'm not advanced enough to know about it, but you can verify what I said earlier with a cheap multimeter

[bigmufffuzzwizz]

What you explained is basically what I know about pots altogether. And I think you answered my question by stating the variable resistor. Has anyone tried putting these two extra pots in? I imagine some versatile results!

[cactus friend]

Ah, sorry - yeah, to answer your question, you'd replace each leg of the resistor you're substituting with pins 1 and 2, or pins 2 and 3, depending upon which direction you want to turn the knob to increase or decrease the effect.  I don't really have room for any extra pots on mine (a trimpot MAYBE) or I'd try it!

[LucifersTrip]

Just found those transistors and they cheap!! 
Definitely wanna give your pot substitution idea a try. Im just not sure how I would add into the circuit. Would lugs 3-2 or 2-1 be connected and then lugs 1 and 3 go in place of the resistors? I would like to learn the theory behind this..

Think of a pot as like a variable resistor, with the middle pin attached to the 'divider' that sweeps along as you turn it.  So, say you have a 100k pot, if it's turned exactly half way, you'll have 50k resistance between pins 1 and 2, and 50k resistance between pins 2 and 3, as it's divided in half. 

Correct, but don't want to confuse bigmufffuzzwizz .   If you have a 100K pot hooked up between lugs 1/2 or 2/3 (2 is middle), then you have a range of approximately 0K - 100K for each.

So in essence, you really only need to use two pins, though it might be a good idea to tie two of them together or ground the third one.  I'm not advanced enough to know about it, but you can verify what I said earlier with a cheap multimeter

The reason you'd tie the 2 together is that you'd still have some connection if the pot dies. Your sound wouldn't go totally dead. I honestly
never do that. You wouldn't ground one of the lugs unless one of points you're inserting the pot into is actually ground (like the volume pot here)

[LucifersTrip]

What you explained is basically what I know about pots altogether. And I think you answered my question by stating the variable resistor. Has anyone tried putting these two extra pots in? I imagine some versatile results!

Yes, I boxed it that way!  You can get a very wide range of tones from the original up to much louder & brutal metallic tones. My friend
was pissed because his ears were ringing when he was done testing it out.

Remember, unless you add a gain stage at the end, the volume of this pedal is low.  I actually left off the volume control and just wired it at 100%.  I also subbed a pot for the 100K resistor. If you make that smaller, you'll get a bit more volume and a fuller tone. You can also sub a pot for the 47K resistor (I did) for even more tones....but that 50K/100K was the most drastic.

[bigmufffuzzwizz]

Thanks for the responses both of you! I need to spend more time around here, you guys are always up to something good! Everything you two are saying makes a lot of sense to me. I've done some more experimenting in general so I understand now what you mean about the pot cutting signal if its not connected or has two lugs tied together. I forgot to include the transistor into my last order but I'll have them at the top of my list next time! I have a lot of mods including a mid scoop knob that should return some of the stolen mids, and a tone stack bypass (easy but first time I figured out how to do it). Plus the 4 pot addition you gave me turns this from a 2 knobber to a handful of knobs  
If I added a simple LPB circuit at the end where the volume knob goes would that work as an added gain stage? Then the volume for the LPB would replace the original volume control and I could leave it off and wire it too 100% like you did correct? But then I would have to tweak the LPB so it doesn't add tooo much volume..Am I going the right direction?