NEED HELP WITH MY NEOVIBE !!!!!

[Zedmin_fx]

Hi,


My brother and I just built two neovibe pedals using parts from mouser, ggg and small bear. We populated our boards and wired them up and our bulbs didn't light up at all, until we put a wire in terminal I and manually touched terminal x with the other end.  I really don't have any idea where to start debugging or what to do, any advice would be greatly appreciated. We really want to get these to work sometime soon. Please help!!!

[DryRoasted]

Click this link for the info needed to help you debug and you'll get some meaningful advice.

http://www.diystompboxes.com/smfforum/index.php?topic=29816.0

[Zedmin_fx]

Ok I will do that but is there a person here who I could talk to directly that might be able to help me out  more? Thanks

[mdh]

The person who wrote the debugging instructions (R.G.) also designed the board, and will almost certainly help you... especially if you follow his debugging instructions

[jsleep]

I think the bulb is one of the trickiest parts of the Neovibe build.  You have to have the correct bulb and then there are some "Fine Print" instructions in the PDF that might help tune in the Buld/LDRs.   

[Zedmin_fx]

Yea I am looking for debugging directions for this pedal. I have it wired up and I put a wire in i,x terminals and that gets the bulb to light up but it doenst flash on one of my pcb's. On the other putting a wire in terminals i,x dosen turn on the bulb.

[mdh]

Yea I am looking for debugging directions for this pedal.

I was referring to the thread linked by DryRoasted... it has general debugging instructions.  You could probably get away with just taking measurements on the LFO at this point, however.  Could you give us voltage readings for Q11, Q12 and the lamp driver transistor?  Also, have you tried twiddling the trimpot?  And if I were you, I'd look for cold solders and solder bridges in that part of the board.

I have it wired up and I put a wire in i,x terminals and that gets the bulb to light up but it doenst flash on one of my pcb's. On the other putting a wire in terminals i,x dosen turn on the bulb.

According to R.G.'s writeup, connecting pads I and X should turn the lamp off, not on.  It seems to me (call it an uneducated guess) that if the bulb turns on when you short pads I and X, then either R47 (the 100k resistor between the collector and base of the lamp driver) is the wrong value, or there's a solder bridge in that area.

[Zedmin_fx]

Ok I am going to get the values later, beacuse I dont have my brothers fluke meter also Should I post pics Of my pbc?? would that help any?

[R.G.]

The more you can tell us about what you did, the better.

I've lost count of the number of people who have posted essentially the same request you did. That's one reason I wrote up the set of instructions in the sticky "Debugging Thread: What to do when it doesn't work". No matter where this starts, I'll ask you for that same set of information before we get done. It's simpler if you just go through it in a straightforward way to start with. Knowing exactly what PCB and schematic you used, what the power supply voltages are and what the pin voltages are on every active device is usually enough to point out what's wrong. It may take a few more questions based on that info, but so far I'm not aware of anyone who really worked on it not getting a working Neovibe in the end.

[R.G.]

Now that I think about it, I wonder how many real Univibes were ever sold, and how that compares to the number of Neovibes built. The Neos have been being made more or less steadily for over 10 years now. Interesting speculation.

[GonzoFonts]

Zedmin_fx,

Yes, post pics of your PCB - top and bottom.

Make sure that the pics are clear with good lighting.

GF

[Zedmin_fx]

Ok, I am back.....I measure 18.3 volts DC input. I am using  a PCB from GGG, nice board!.  q-11 and q-12 behave as though voltage passes right through them. I measure 17.6 vdc (collector), 17.5 vdc (base), 17.4 vdc (emitter). base to emitter, 0 vdc, collector to emitter, 0 vdc.......HMMMMMMM!!!!!!!!!!  No solder bridges are present.  my guess is that the transistors are bad. 
Q-13 17.6 (collector), 8.9 (emitter) 9.4 (base).   E to B measuring 0.5 vdc.       Q-1  measuring  2.5 vdc on collect, 1.4 on base, 1.0 emitter


Q-2

5.4  c
2.5 e
2.0 b
.5 e to b

Q-3

11.1  c
5.4  e
4.7 b   

.5  e to b


Q-4
15.4  c
7.3 e
7.8 b
.5 e to b

Q-5 
10.0 c
6.8 e
6.3 b
.6 e to b

Q-6
15.4 c
7.4 e
6.8  b
.5 e to b

Q-7 and 9  are very close to Q-5
Q-8 is the same as Q-6

Q-10

15.4c
10.9e
11.2b
.5 between e and b

[R.G.]

Ok, I am back.....I measure 18.3 volts DC input. I am using  a PCB from GGG, nice board!.

Thank you.

q-11 and q-12 behave as though voltage passes right through them. I measure 17.6 vdc (collector), 17.5 vdc (base), 17.4 vdc (emitter). base to emitter, 0 vdc, collector to emitter, 0 vdc.......HMMMMMMM!!!!!!!!!!  No solder bridges are present.  my guess is that the transistors are bad. 

You see why I wrote that up as I did? You are very close to solving your own problem, just because you knew what to measure. But you've made a bad guess.

It is always best to proceed on the assumption that all parts are in fact good and only as a final, last ditch resort decide you have bad parts. Modern transistors are remarkably good, and the chance of getting a completely shorted one are maybe one in a million. The chances of getting TWO that are bad in exactly the same way, and having them be next to each other on a PCB are astronomically huge. It is possible, of course, but so unlikely that I'd bet on other things first.

For instance:
(1) Are you SURE there are no solder bridges? Under what optical magnification did you check? Solder threads can be thinner than a human hair.
(2) Are you SURE there are no copper shorts on the PCB? It happens sometimes, even on the best PCBs. That's why for high volume production, the maker will produce a "bed of nails" tester to test every single path for open and shorts on every single board. Think about optical magnification and running a knife between the pads
(3) You notice that the voltages all seem like they're near the collectors. What would happen if the emitter leads were open? Could that cause what you're seeing?

[george]

what sort of transistors are you using?  2N5088?, 2n3904, BC549? 

I'm just wondering if pinout is the issue here

[Zedmin_fx]

I am using BC 548C...mouser sells them as a 2n5088 work-alike.

[R.G.]

I believe the pinout on the BC series is different from the 2N5088 and 2N3904. Pinout differences are one reason I put that "any substitutions?" question in the debugging instructions.

[Zedmin_fx]

ok, well i suppose that serves as a viable amswer! I will  have to order  new transistors....i will  get the 2n3904 version.  I found the spec on mousers website....looks like the pinout is backward froom the 2n3904..(collector and emitter are reversed). would it net me anything to flip them around? or would it be best to get the right version?  I dont want to traumatize the board....what do you all think?

[Zedmin_fx]

also, would it be at all profitable to switch the 1uf electrolytic caps to ordinary metal film? not only  do i want a univibe, but i  want to make sure it offers a transparent, high fidelity-type tone... will this do much for the overall tone of the pedal or is it just hype?

[mdh]

First try flipping the transistors around.  Once you get it working, you can worry about whether you want to mess with the caps.

[Zedmin_fx]

OK I will try to  flip the resistors, I just don't think I will have allot of the leads left, so it might be tricky!!