Neovibe Help - Bulb not pulsating

[wicker]

Hi,

I have been sitting on this for about a month now trying to read and trouble shoot, but I am stuck, any help is great. The bulb is not pulsating. I think the issue is in Q11 or Q12 area...

I do get a bypass signal and a wet signal that I can get to pulsate by manually adjusting the trimpot.

Using: GGG PCB Board polulated with all new parts from Mouser and Small Bear so this is my messu, somewhere... I did the resistor change for true bypass volume drop, I used L7815. The adapter I am using is: https://www.mouser.com/Search/ProductDetail.aspx?R=WAU16-400virtualkey55310000virtualkey553-WAU16-400

Transistors used: 1-12 2N5088 13 2N3904

I have gone through and verified (the best of my ability so far) that there is no solder bridges with lighted magnification and an xacto knife. When verfiying parts and positioning I did have the Lamp driver incorrectly placed.

I can provided pictures and additional measurements later, this all I have so far (no computer at home, only at work)

These are the measurements I have so far...
Q1
C 1.687
B 1.317
E .902

Q2
C 5.01
B 1.68
E 1.428

Q3
C 10.36
B 5.01
E 4.41

Q4
C 14.93
B 4.72
E 4.33

Q5
C 11.20
B 4.33
E 3.75

Q6
C 14.93
B 4.72
E 4.33

Q7
C 11.19
B 4.33
E 3.75

Q8
C 14.93
B 4.73
E 4.33

Q9
C 11.21
B 4.33
E 3.75

Q10
C 14.93
B 5.96
E 5.45

Q11
C 22.87
B 14.48
E 22.95

Q12
C 22.94
B 22.97
E 0.00

Q13
C 15.57
B 2.27
E 1.61

DB
8.61 -> 23.09
8.33 -> 0.00

L7815
IN 23.27
Gnd 0
Out 14.93

[richon]

does it sound?

if so, what if you put the 50K (depth) to maximun... does it light the BULB?

what value do you read at the trimer for the intensity of the light?

[wicker]

does it sound?

Yes

if so, what if you put the 50K (depth) to maximun... does it light the BULB?

The bulb is lit, it doesn't pulse, the 50k has no effect on the bulb intensity. The only way to change the intensity is through the trimpot.

what value do you read at the trimer for the intensity of the light?

I will check tonight when I get home.

Thank you!!!

[R.G.]

I have been sitting on this for about a month now trying to read and trouble shoot, but I am stuck, any help is great. The bulb is not pulsating. I think the issue is in Q11 or Q12 area...

You're right. It is.

These are the measurements I have so far...
Q11
C 22.87
B 14.48
E 22.95

Q12
C 22.94
B 22.97
E 0.00

These are the pertinent measurements.

1. Are you sure the transistors are inserted correctly?

2. It appears that Q11 may have an open emitter, or its emitter may not be properly soldered.

To debug further, please provide the voltage to ground at each end of each component in the LFO section. That will either tell us what else is causing it or isolate Q11.

Your problem is quite similar to a number of others.

[yeeshkul]

Q12
C 22.94
B 22.97
E 0.00 ??

start here - the emitter should not be at the ground at all:
- check R46
- use magnifying glass for hair bridges around Q12 - be really suspicious, remove everything between the lines ....
- reheat the tin on the crucial parts and pull it along the circuit lines
- remove R46 and measure the voltage on the Q12 emitter again
this should not be difficult to sort out

"Your problem is quite similar to a number of others."
yeah, i had the exactly the same problem - i used crappy DC source and cheapo 1Mohm multimeter - they give WRONG voltages on big resistances (however 0 is 0 haha). it took me a week to realise.

[wicker]

Here are the voltages I took from LFO:

R39 13.97 23.75
R40 13.98 15.31
R41 13.95 0.00
R42 0.00 0.00
R43 0.00 0.00
R44 0.00 0.00
R45 0.00 0.00
R46 0.00 0.00
R47 2.67 19.04
R48 0.00 .501
R49 2.66 2.67
R50 2.67 0.00
Trim .545

+/-
C19 15.30 0.00
C20 0.00 0.00
C21 0.00 0.00
C22 0.00 0.00
C23 3.13 0.00
C24 23.73 0.00
C25 23.73 0.00

D1 0.00 0.00
D2 0.00 0.00

Pots all 0.00, E D C G H F I are 0.00 , X is 2.67

Will Post photos when I am able...

Thanks

[R.G.]

OK. It is very likely that Q12 is open base to emitter.

The only thing to answer is whether you measured on the transistor pins themselves or on the pads or traces that the transistor pins solder to. If you measured on the transistor pins, replace Q12. If you measured on the board/traces, re-solder the pins of Q12.

[wicker]

Ok,

I resoldered everything around Q11 and Q12 and busted out the xact to eliminate the possibility of a solder bridge, nothing...Still sad, replaced Q11 and no change, though it usually is not a bad part. I replaced Q12 and there it went. Perfect!!! Being new at pedal assembling, I figured a bad part would not factor in, I was sure I had messed something up. It's nice to add that as a possiblity of things that can go wrong!!!!

Thanks to everyone for their help!!! It is much appreciated. I really should have swapped those 2 parts out before asking for help since I could recognize the issue was around there, I just really didn't trust myself and assumed it was my error (like it usually is), I guess...

I have to resolve some distortion/noise issues, but I can read/research that, and it makes it much easier to do when the unit works.

Thanks RG for this layout and the help, this is my holy grail effect...

I will tell you this though, I learned a lot more this way, than if it had worked first time I plugged it in.

-Brian