Gain pot not working

[zener]

I recently built  Doug's new fuzz pedal http://home.cfl.rr.com/dbhammond/GS_Tonebender.gif.

The gain pot is not working when I switch the 10uf cap on. It seems to be at full all the time.

At once, I thought it is working. It is, but probably it's barely audible.

I know another one here who's having the same problem. His problem is worse. his gain pot is not working without the 10uf cap.

Hoping Doug will figure this one out. Anything from anyone, of course, will be greatly appreciated.

Thanks :wink: .

Zener

[javacody]

zener, that switch looks like a pretty basic addition. What layout did you use?

[smoguzbenjamin]

Check your wiring, cause the 10uF cap just lets more bass through and has nothing to with the gain pot. Higher cap = more bass

[zener]

I checked the wiring already. It's basic doing that whenever there's something wrong. What bothers me is that there is someone out here that also have the problem. It makes me think that there might be something wrong from the schem itself unless proven otherwise.

Another thing, we (me and Bill_F) used different layout for our build. I made my own, he made his own and ended up having the same problem.

Here is the layout I made using ExpressPCB:  http://www.angelfire.com/weird2/zener/Hot_Silicon.pcb

Take note that I missed the R10 from C5 to ground in the layout. I was able to soldered it in the board, so it's not the issue.

Thanks for any help.

Zener

[smoguzbenjamin]

Hmmm. You should buy a breadboard to test circuits  before building them. Saves a lot of hassle if it doesn't work They're kinda pricey though. Anyway, your build:

I can't see why letting more bass thru would affect the gain pot in any way. I'm baffled as to why that is. The fact that someone else has the problem, but in reverse as it were, makes me think that it's human error, and not something wrong with the schemmo. I make mistakes all the time, lol. Anyway, if you haven't checked for hairline fractures on your PCB, do so. If there aren't any and you're 100% sure you got all the wiring correct... Then I donno. Make sure the values are correct, though.

Oh hang on, did you wire the caps in series? Because that could be a problem. if you wire them in series they will act as a single cap of 0.009uF. That might explain it. It'll roll off the higher frequencies as well.

Check your PCB for any errors you could have made.

[javacody]

No, he's got em parallel.

[smoguzbenjamin]

Wierd. All I can say is check the layout and check for fractures. Other than that I have no clue

[javacody]

I haven't checked the pcb thouroughly, and I'm real new at this anyway, so I probably wouldn't find anything, but I'm wondering if there is a solder bridge somewhere that shouldn't be?

[smoguzbenjamin]

Just go over every solder joint. And all you need to to see a hairline fracture is to look carefully, just look to see if everything is ok.

I started FX building 3 months ago, and I prefer perfboard, so I don't use PCB's much. But I've fixed a few PCBs for some friends and so I do know that you should just look, so don't be so negative about your capabilities! I think that if there was a hairline fracture in the copper tracks, you'd find it. You can't do better than your best.

Give it a shot.

[Bill_F]

Hi guys. I'm the other one having problems with this schemo. Both Zener and I did separate layouts and ended up with the same results. The gain pot does nothing. I have checked my layout against the schematic over and over and can see nothing wrong. This makes me wonder if there is a problem with the schematic. It would be strange for us both to have a hairline crack in a trace at the same exact place. Has anybody else built it?
I've put mine to the side until this can be sorted out. Right now I've entered a building binge. I have five projects going on at once (all at different stages and all waiting for different parts). I'm presently working on the MXR envelope filter, the Small Stone, the AD3080 delay, the Ibanez flanger and the Meteor. Hopefully I'll have all these done by the end of next week.  :lol:

[smoguzbenjamin]

Wierd. Try leaving the gain pot out, and use the 5k pot as a volme control before Q2. Maybe that works better.

[zener]

I'm glad that Bill posted on my thread to substantiate my problem.

Thanks Smoguzbenjamin and Javacody for the effort of trying to figure out our problem. :wink:

Yes, I do have a breadboard. In fact, when Bill_F and I discovered this problem, my circuit is still in the breadboard.

Doug H., please help.

Thanks

Zener

[Joep]

Hi Zener,

You forgot R10 in your layout. This one connects the emitter of Q4 to ground.

I think this is the problem

Good luck,

Joep

[zener]

Hi Zener,

You forgot R10 in your layout. This one connects the emitter of Q4 to ground.

I think this is the problem

Good luck,

Joep

Yes, the R10 is not in the layout but I was able to solder it on top of the board from ground to the pin of C5 connected to the Q4 emitter. I made sure that the R10 is not shorthing anything

[zener]

I'm so sorry for bugging everyone :? . The gain pot is now working. I don't know what I did , it just worked. But I swear, before it's not working. Twice, while in the breadboard and in the PCB.

What made me feel that there might be something wrong with the schem is that another one from here had the same problem. We used different layout.

I feel so stupid for  bugging this forum for a problem that suddenly fixed itself. :roll:

Some sort of abra cadabra or gain pot open sesame  :shock: ? I don't think so.

Still, I wanna thank everyone for bearing with my "problem that never was".  :roll:

To Bill_F, I really have no idea why the gain pot of our build before didn't work. Feel free to use the layout I posted to double check yours.

Zener

[smoguzbenjamin]

70% is knoledge, 30% is voodoo

[zener]

70% is knoledge, 30% is voodoo

Maybe Bill and I were struck by the 30% thing. :lol:

[smoguzbenjamin]

Probably.

It took me two goes to get the beginner project (NPN boost) going on perf. Same voodoo. It just seems to happen every once in a while  :roll: