My Newest Fuzz Project

[italianguy63]

Anybody?

I have not had time to get back to it.  I desoldered the cap and broke off the ring wire in the process.  Now I have to desolder that.  Frustrating.

Is the 2N3906 fragile?  I figured since it was Si, I did not use heatsinks when I put it in.  Could it be damaged?  I don't think I overheated it, I hit it pretty fast...

MC

(edit-- if it matters, the ring connection is on the output jack).

[italianguy63]

Bueller?

Built another one fresh.  Same problem with the transistor switching.  What gives?

[italianguy63]

Would lowering the value of R2 (or C1) help?

[italianguy63]

This is from R.G.'s posting.. but from what I can find on "PNP transistor switching"-- R1 is usually 10x R2.

Maybe R1 is too small???, maybe R2 is to big??  maybe C1 is causing the problem???  I've used this before on other pedals without issue.

Anybody?  (dead telephone).

[italianguy63]

OK-- A bit more information.  Maybe eventually somebody will bite.

Decided to just start from scratch with all new components, and do a meticulous build.. starting with the most basic fuzz with no bells and whistles.  Did it and I have a basic fuzz working.

Strangely the signal/gain seems "weak" and the fuzz seems "weak."  The circuit is identical to a DA-67, but the sound seems "off"-- I'm perplexed.  I put sockets in for the trannies, and I tried about 4 or 5 different combinations.  They all seem "weak" in sound although the bias voltages are good, and everything seems to be OK.  Weird.

But, back to the transistor switching problem... Seems, I have not been patient enough.  OK.  If I plug everything up... and wait....

About 5 seconds pass.. then I hear a faint "jet engine starting" tone...  constantly rising tone.  Goes on for almost a minute.  Then it stops for about 3 seconds.  Then I get a "Pop!," then the charge pump starts passing voltage after another second or so.  How does that grab you?

When I started this particular troubleshooting build, I left C1 out... The events listed above still happened, but the time was closer to 20 seconds instead of a minute.

MC

[duck_arse]

I know 0 about the charge pump ic's, but just so's you're not left talking to yourself, have you tried disconnecting the polarity protector transistor, and powering up to see if this is not the normal operation?

and you could try using the protection transistor to power something simple, like a led + clr, and see if you get a time delay to full bright.

[italianguy63]

Thanks-- I was getting lonely.   

Strangely, I have seen this like once before (this board).  I have a bunch of these boards made where they are the voltage inverter (charge pump) only.  And they for the most part have worked flawlessly.  I am totally lost why when I have added the fuzz circuit to it (this PCB), I am having this issue full press!

I'm at a loss.  I don't understand RG's circuit well enough -- so everything I am trying is just shots in the dark.  But, It does not seem to do anything if I short out R1 or R2... It seems to do with the caps becuase of the charging (sound effects).  Definitely the sound of the cap(s) filling.  Really, I'm lost.

I don't know if I got a batch of a bad component or what!

I am not satisfied with the sound of the fuzz circuit either.  I am in the process of building one out with the charge pump eliminated (and battery power jumpered in).  That way I can isolate if I have something else wrong too.

Seems the "Treble Bleed" pot does not have any effect.  This build seems cursed!  I'll figure it out eventually.  I'm tenatious that way.

MC

[Mustachio]

Hey Mark I was looking at this yesterday , didn't get very far but I'm planning on populating it later tonight ill let ya know what I find. I'll compare it to the charge pumped fuzz I put together a lil while back.

I sort of remember yesterday looking at r1 and r2 and thinking its a voltage divider dropping the 9v in to some where around 7.8v for the base of the 2n3906 . I'll have to look tonight shouldn't take long to populate it.

Hang in there man , I meant to post yesterday that I was looking at it I just didn't get around to any real world testing yet.

Cheers buddy the board looks great I'm sure there will be an easy fix

[italianguy63]

Thanks Jim-- in the big picture... I'm not worried about it.

I am probably too close to the trees, and trying too hard.  It is probably something dumb.  I set it down today, and finished my 2nd Dyna Comp today.  I happened across a couple metal can CA3080's so I made one of each (metal vs. DIP).  They both work great.  Side by side, the metal can 3080 sounds slightly brighter.

So, I did accomplish something today (I actually rearranged my garage too).

I'll get this licked eventually.  I have 50 boards to work with..   

Please let me know what you find.  I am still pretty stoked with it; it should turn out to be a cool board with lots of potential and a good variety of options.

MC

[italianguy63]

A small amount of progess to report.

My "fuzz" issues appear to just not finding the right "pair" of transistors yet.  I have been able to swap them around now that I have a socketed prototype.  Yeah, the trannies are altering the sound, but I have yet to find ones that sound good.  (Which makes testing the other parts difficult).

Seems some of the bad/weak sound was my output cap (C6) for my co-builders.  Took out the mylar, and put in a poly/film.  Big difference.

Treble bleed seems to work.  Hard for me to tell because my hearing is shot.  But, it seems to take the very top edge off the treble only.

I previously confirmed sag and bias pots seemed to work with the values posted.

So, only the weird charge pump (transistor switching) issue still to figure out.

MC

[italianguy63]

OMG...  **PRIMAL SCREAM THERAPY!**   

Bad charge pump IC.   Days and days of troubleshooting.  Most obvious problem skipped.  I must have moved the IC (and the problem) to both test platforms.

MC

[haveyouseenhim]

So is it confirmed working now?

[italianguy63]

Yep.

[haveyouseenhim]

Yep.

I can't wait. I have to get in my new house before I start any more builds.

[italianguy63]

Bigger reply:

Weak fuzz was trannies.  I threw in some AC128's-- it came alive.

All the pots with the posted values all work.  The only one that doesn't seem to do much is the treble bleed.  Maybe somebody can play with the values and improve it.  In theory, it should work.  Again, maybe my hearing.  My high frequency hearing is shot.

The power switching problem was a huge Snipe hunt.

[italianguy63]

Snipe hunt in HAM radio lingo "Novice Trick."

[duck_arse]

"a trap for young players"?

[italianguy63]

Epilogue:

I have been going through the carnage that was the protypes I was fighting with.  I have found multiple bad charge pump IC's.  I must have gotten a bad run of them.  I will need to check them all going forward.

MC

[bluebunny]

I have found multiple bad charge pump IC's.

What charge pump IC are you using?  Went back through the thread, but couldn't spot a part number...

[italianguy63]

The ones that seem to have the issue were TC1044SCPA.  I replaced them with ones I bought on a seperate occassion, and they were TC1044SEPA.  I have used them before with no issue.  I think I might have just gotten a run of questionable ones..