Neovibe Debug Help

[tr1p1n]

Though I'd straighten this up for someone who's willing to help. Followed the Debugging list.
1. When I plug the jacks in I get a loud and constant waaahhhhh from my amp and nothing from my guitar, but i can like mute the strings to cut 90% of the wah noise out. So pretty mcuh I cant bypass the signal let alone getting the effect to even work. The bulb works and used to be able to control it with speed/depth knobs. But after checking transistor voltages come to find out now the bulb just stays on and does nothing when I probed Q13 I think it did something weird, as now when I touch it certain ways it glows brighter or shorts out.
2.Neovibe
3.Source geofx
4.Volume mod as followed in R.G's guide.
5.No part substitutions.
6.Positive ground to negative ground. No?
7.I measured the transistors values (all 2N3904) and are lower down in this topic. But it also said while waiting probe the electrolytic caps and make sure + v is greater then - . All look good except C19 which + is like 2v and - being like 18v something.

[tr1p1n]

Now I can sorta get a signal, only when I hold the wires on the jack it like comes in and out all distorted :/ still any help at all would be appreciated.

[lonewolf]

the ldrs do not glow..they react the the bulb...the light cover has to be on also or you will get a loud noise and no effect...getting it to sound right involves adjusting the bulb on-off cycles with trimmers and the placement of the ldrs effects it a lot...I used the hermetically sealed ones and laid them flat facing up.... reflective light sounded better than direct light

[tr1p1n]

Holy crap really!? Im going to go build the light shield really quick. I seriously hope this is the problem....Oh and thanks for the info about the LDRs i was thinking the whole time i burned them out or something.

[tr1p1n]

Still just waahhhhhh coming through my amp and no effect. Plus the DPDT switch doesn't seem to do anything, no matter what the pedal is always on unless it supposed to be like that. But when I do click it, the wahhhhh is really loud, but when I click it again the wahhh is very very subtle. Do you think I have the jacks wired up wrong? and did you check the part i was talking about, I have two of them. Im really really new to all of this so I don't have the slightest idea as to whats going on.

[lonewolf]

did you use a printed circuit board? if you have a meter you can check voltages on the trans pins..then post them..also dbl check the wiring connections...what ldrs did you use? how did you install them? what bulb are you using?this circuit is not hard to get to work,but getting it to sound right is something else..the voltages are on theGGG page ..did you wire it true bypass or the original way which turns off the bulb?..if you cant bypass and get a clean signal ..something is wrong with the switch wiring for sure ..you can bypass the dpdt and connect directly to the jacks..post pics of your board,etc..use a magnifyer and check the solder joints...

[tr1p1n]

Hold on a few minutes and ill have everything (almost).

[tr1p1n]

did you use a printed circuit board? if you have a meter you can check voltages on the trans pins..then post them..also dbl check the wiring connections...what ldrs did you use? how did you install them? what bulb are you using?this circuit is not hard to get to work,but getting it to sound right is something else..the voltages are on theGGG page ..did you wire it true bypass or the original way which turns off the bulb?..if you cant bypass and get a clean signal ..something is wrong with the switch wiring for sure ..you can bypass the dpdt and connect directly to the jacks..post pics of your board,etc..use a magnifyer and check the solder joints...

Yes, the PCB was bought from General Guitar Gadgets. I do have a meter, but how do I go about measuring the transistor pins? Well as far as the jacks go, think everything is wired correctly. The LDRs were purchased from small bear Photocell Silonex NSL-7532 and I installed them as flat as I can get them to the board using the farthest holes of 2 (if that even matters). And I guess I wired it true bypass, just followed the wiring diagram that comes with the PDF from general guitar gadgets neovibe pcb section. And yeah that's when I new I messed up, if it didn't bypass it wasn't gonna work period. And about bypassing the DPDT, like I said I'm new, the only knowledge I have about any of this stuff is some common parts names and how to check the resistance of resistors and that's it, literally. Solder joints look fine, well some may look like crap but (just sloppy looking not cracked or cold) they got a good connection, at least i assume.

http://s1048.photobucket.com/albums/s361/empyre18/    -    Pictures of jacks, pcb, pots, wiring, ect. Oh and if something looks wired wrong ask me about pot/switch ect and the color and I'll tell you if it goes to the correct corresponding letter or where ever it may be. Just hope we can resolve this quickly.

[tr1p1n]

Can anyone point me in the right direction? Or atleast explain to me how I can test the transistors and what not? I've tried and some say 1000 others say like 42, I don't know whats going on.

[lonewolf]

to test the transistors set your meter on dc volts..connect the black probe to ground..I would use a alligator clip ..then place the red probe on each one of the trans pins carefully and write down the values for the e/b/c..compare them to the voltages on the schematic..make sure they are in correctly...I would also make sure you have all of the electrolytics correct..check polarity... if you disconnect the in/out wires from the switch then you can connect them to the jacks (again with alligator clips)thats where I would start....

[tr1p1n]

if you disconnect the in/out wires from the switch then you can connect them to the jacks (again with alligator clips)thats where I would start....

Could you please elaborate? Don't quite understand.

[lonewolf]

connect one side of the meter to the ground the other to the pins on the transistors one at a time...set the meter to dc volts(around 20v scale) ground is pad L ..you can connect  to the ground connection on the in or out jacks...you say you have a loud waa that is affected when you touch the strings...that could be a open ground problem somewhere...check continuity on all your ground points to make sure nothing is open

[tr1p1n]

So here's what I got for the transistors them being all 2N3904's by the way. Oh and I did that continuity check and it seems all the connections and such are fine.

Q1:                             
C = 1978mV
B = 1227mV
E = 781mV

Q2:
C = 4.48v
B = 1.97v
E = 1367mV
Q3:
C = 10.69v
B = 4.48v
E = 3.85v
Q4:
C = 14.79v
B = 4.46v
E = 4.07v
Q5:
C = 11.32v
B = 4.10v
E = 3.38v
Q6:
C = 14.79v
B = 4.85v
E = 4.4v
Q7:
C = 10.83v
B = 4.4v
E = 3.76v
Q8:
C = 14.79v
B = 4.67v
E = 4.21v
Q9:
C = 11.08v
B = 4.21v
E = 3.57v
Q10:
C = 14.78v
B = 6.05v
E = 5.5v
Q11:
C = 26.3v
B = 18.3v
E = 25.7v
Q12:
C = 26.4v
B = 25.5v
E = 25.5v
Q13:
C = 19.43v
B = 3.83v
E = 3.22v

[lonewolf]

your voltages on q1 thru 10 look ok but the emitter voltage on q 12 should be around 10v ..25.5 seems very high..I have a darlington pair for the bulb driver so I cant compare that..you should also have 11.7 volts at the r 39 r 40 junction..my 7815 reads 20v in 15v out..plus I used 2n5088 for q1-10 and 3904 for q11-12

[tr1p1n]

So what should I do about Q11 change it out? and r39, r40 junction? No idea how to check the voltage there. But same for me on the 7815.

[tr1p1n]

Anyone got any insight? I checked the solder joints, all appear to be fine and I also checked all the resistors too. No idea as to what I should do now though.

[R.G.]

If the meter readings are correct, Q12's emitter is not connected to anything to pull it towards 0V.  The readings are what I'd expect if Q12 emitter was either open internally - which is the least likely scenario - or otherwise is not connected to R44, R45, and/or R46. This may be a soldering problem, a bad/open trace, or some other issue. That's where I'd check with a magnifying glass.

Here's a trick that may help. Your multimeter also measure resistances. If you set it to the lowest resistance range and connect the two probes together, you read the "resistance" of zero ohms. Your meter may or may not show zero, but that's OK - errors are hard to get rid of at really low resistances. Once you know that "zero resistance" looks like, you can put one probe on any two points that should be connected together according to the schematic. If they really are connected, you'll get that "zero resistance" reading, whatever it actually was. If they're not really connected, you'll see something much larger.

I recommend you clip one probe to the emitter of Q12, and go see what the actual resistance is to the terminals of R44, 45, and 46. One end of each of these ought to show nearly zero ohms. If not, you've found at least one problem if not THE problem.

Debugging is like peeling onions: each problem lets you see the next layer of problems, and you cry a lot. 

[tr1p1n]

Well measuring between Q12 and 44,45,46 shows 0.01 resistance, assuming that's the zero or bottom line for my multimeter. And as for the new readings I guess
Q12:
C = 27.5
B = 26.5
E = 26.6

And R.G any explanation as to why the bulb doesn't work now? It's only when I started probing transistors that the bulb just stays on now, doesn't respond to depth/speed anymore but it does flicker and short out when messing with Q12. Oh and will switching the transistor out make a difference?

[lonewolf]

you can short out the bulb driver transistor if not careful.the oscillator is controlled by those 3 transistors(Q 11/12/13).look at the layout and you will see where r 39 and 40 connect on one side ...that junction should read 11.7 volts...all the voltages are in yellow boxes...I use sockets for transistors/IC's and for caps sometimes as well so I can swap things out easily.. also when you do continuity tests to check for open connections or shorts etc..do it with the device off..just follow the layout and check point to point to make sure everything is right..and use a jewelers magnifyer to check the solder connections..the wiggle test will expose possible cold solder joints also..

[tr1p1n]

Do you think that's what happened with the bulb? it USED to pulsate until i checked the transistors but then again if I burnt out the transistor it wouldn't give me any readings right? And if not do you think I should swap them out? Bought a bunch of 2N3904's. And how could I test that junction for r39 and r40? I don't really know how to go about doing that...Last time I did the continuity test power was on and I literally just got done doing what R.G suggested by checking resistance between each point on the board (fixing some bad joints and what not) but that's sorta the same test right? So the points are good, checked the resistors earlier, caps are good except C19 still I think, negative v is higher then +. And for the diodes, rectifier ect. ect. are all in the right places, so little of them anyways. So let me know how to check voltages at different points according to the schematic, oh and thanks for being so patient with me. I really hope we can see this through to the end.

Actually I think I got it....Grounded to pad L checked voltage by r40 and r39 both say 15.8v. So im assuming something is happening between here and Q10? Q10 voltage pretty much matches up and so do the ones before that, given + or - a few which I'm guessing isn't bad? I mean there not to far from being dead on.

Also went ahead and did the continuity test. All points on PCB are good and all pots, jacks ect. wired good.

And.. Like an idiot, impatient on waiting for someone to come around and offer insight (as I've got no clue what to do next, such a hopeless feeling its making my head spin, just wanna jam some machine gun sooo bad  ) anyways removing a transistor to see if changing anything would help but to no avail the metal like contact ring fell of from the bottom. Bad? or am I just plain stupid? Assuming stupid but then again I only have roughly 3 days of soldering/de-soldering under my belt haha. Anyways the circuit still works, voltages all the same....hope it doesn't short or something someday because of that. Unless the contacts are just there so the parts won't move....no idea.