Neovibe Debug Help

[tr1p1n]

get the weller iron it will  pay for itself because you wont have to replace the tips  and the heating element is replaceable too

So for the mods all I need to buy is the 220k and 250k trimmer? Failed to mention, could you show me on mouser what specifically to get? there's to many to choose from.

[lonewolf]

the 220k I used for the output mix mod although they call for a 200k ..220k is what I had and It worked great..the 250k trimmer is for the bulb driver offset mod and I found that a 20 turn trimmer allowed for a more precise adjustment..but I had more space since I made this with a perfboard..I looked at the picture of the GGG board and It looks like there is a spot for the mix trimmer...you would remove the 2 100k mix resistors (R35-36)but I dont see a place for the bulb offset trimmer so that would have to go to a separete board..that trimmer works best with a darlington pair (2 3904 trans)..check out the forum-vibe site and look at the modified version(not the red house)..you still need to fix the current problems before you start modding anyway..best advice I can give you is before you commit to building a pedal..do lots of research to check for modifications(before you build the circuit)

[tr1p1n]

the 220k I used for the output mix mod although they call for a 200k ..220k is what I had and It worked great..the 250k trimmer is for the bulb driver offset mod and I found that a 20 turn trimmer allowed for a more precise adjustment..but I had more space since I made this with a perfboard..I looked at the picture of the GGG board and It looks like there is a spot for the mix trimmer...you would remove the 2 100k mix resistors (R35-36)but I dont see a place for the bulb offset trimmer so that would have to go to a separete board..that trimmer works best with a darlington pair (2 3904 trans)..check out the forum-vibe site and look at the modified version(not the red house)..you still need to fix the current problems before you start modding anyway..best advice I can give you is before you commit to building a pedal..do lots of research to check for modifications(before you build the circuit)

Well I figured I'd get them ahead of time while I can. I know I need to fix this current problem first and then the bulb not oscillating (think that's what you call it, R.G said i've damaged something there too but I may or may not need new parts). But with awesome guys around like you and R.G im not to worried about fixing it. One way or another it will be fixed and when that time comes I'll be ready to mod. But as for the separate board I think I should put that one on hold, seems like a whole different ball game. Then again I'm still learning so I've got no idea.

[lonewolf]

worry about the bulb offset trimmer if you cant get it to sound right after you get it working..you can get 250k trimmers from mammoth to do the mix mod..otherwise you should check out thaishine on ebay...a lot of the stuff they sell ships from the us and 4 days delivery and great prices...they have the 200k trimmiers and the multi turn... as well as lots of other components...they are related to tayda..a remote board for the bias offset is not difficult at all...much easier than this troubleshooting fun you are having

[tr1p1n]

worry about the bulb offset trimmer if you cant get it to sound right after you get it working..you can get 250k trimmers from mammoth to do the mix mod..otherwise you should check out thaishine on ebay...a lot of the stuff they sell ships from the us and 4 days delivery and great prices...they have the 200k trimmiers and the multi turn... as well as lots of other components...they are related to tayda..a remote board for the bias offset is not difficult at all...much easier than this troubleshooting fun you are having

Will do, ebay was my primary choice when I'm gonna stock on parts for my next pedals. A remote board? well as long as you say it's not difficult I'm sure I can manage, but as for the "troubleshooting fun" haha kinda hard to have fun when you've got no clue as to what's going on or what to do next but I'm learning and that for me is enough fun in itself. But when this is all said and done it will be so worth it.

[tr1p1n]

So I've got the parts, switched out C22 and no change. Still getting voltage to G & H. No clue as to where to go from here.

Changed C23 also, same thing. G=8V  H=3V  F=0.

[tr1p1n]

Anyone offer any help?

[R.G.]

Measure G, H, and F.

Pull OUT C22.
Measure G, H, and F again. Did it change?

If no, pull OUT C23.
Measure G, H, and F again.

Let us know what happens.

[tr1p1n]

Measure G, H, and F.

Pull OUT C22.
Measure G, H, and F again. Did it change?

If no, pull OUT C23.
Measure G, H, and F again.

Let us know what happens.

C22 out w/ C23 in

G=0
H=160mV
F=0

C22 in w/ C23 out

G=jumped to 16v, went back to 13v before it started dropping. Jumps around to much to really get any accurate reading.
H=0
F=0

C23 & C22 out

G=0
H=0
F=0

[R.G.]

C23 & C22 out
G=0
H=0
F=0

OK. F is connected to ground and the depth pot is a resistor. Therefore, with only one terminal connected, and that one to ground, all terminals show zero volts with respect to ground - which is what should happen.

C22 in w/ C23 out
G=jumped to 16v, went back to 13v before it started dropping. Jumps around to much to really get any accurate reading.
H=0
F=0

DC levels are right, but G moves around a lot. This seems to me like the LFO is running OK.

C22 out w/ C23 in
G=0
H=160mV
F=0

Mmmm. Very odd. C23 seems to be feeding DC back into the wiper of the depth pot.  Are you **=>>sure<<=** that C23 (and the other electro caps) are installed with the correct polarity?

[tr1p1n]

Yep all the caps are oriented the way they should be. No idea what's going on, still can't get any reading's on that part of the board either, Aside from the caps.

[R.G.]

Much as it pains me to say this, we're rapidly approaching the place where it can't as a practical matter be debugged remotely.

We're left with things which are very unlikely or can only be found with hands on the board. It is possible the bulb is open, so you ought to check that out. It is possible that Q13 was damaged in the process; that ought to be checked as well. It is possible your meter is telling you untruths. It is possible that there is more board damage than you have been able to spot yet. There are other, even more unusual possibilities as well.

None of these are show stoppers, but it gets very difficult remotely.

My best guess at the moment is that the LFO is working, but the lamp and/or driver is not. To debug, pull out C22, put in C23, measure all working voltages on Q13 and the bulb back to the terminals of the depth pot. Also, measure the voltages on the depth pot while slowly turning the pot knob. Do they vary? If the voltage on the collector of Q13 is always zero, the lamp may be open. If it's always very high, the emitter circuit and trimmer pot may be open.

[tr1p1n]

We're left with things which are very unlikely or can only be found with hands on the board. It is possible the bulb is open, so you ought to check that out. It is possible that Q13 was damaged in the process; that ought to be checked as well. It is possible your meter is telling you untruths. It is possible that there is more board damage than you have been able to spot yet. There are other, even more unusual possibilities as well.

Hands on the board? Do you mean my hand could be giving us false readings or something of that sort? As for the meter, it is quite old. Borrowed it from my uncle who had it sitting in his garage for I'd imagine 20+ years, but it was unopened. And for the board damage, none that I can see but I sure hope there isn't any. Messed up quite enough already for this project.

Now for the readings.

Q13
C=19.54V
B=3.51V
E=2.92V

Bulb - Is there supposed to be continuity between the two bulb points? Might be a silly question, but just checking.
Depth side of the circuit = 26.9V
Opposite side = 19.64V

C23
+ = 3.55V
- = 0V sometimes I get 001mV, but 0 for the most part.

Depth
G=0
H=0
F=0

Forgot one thing, Could not having the depth pot wired up give us these weird readings? Earlier when doing the tests I measured voltage without the depth pot wired and was getting 3.27V in H before slowly dropping, the others being 0V. Then of course after having it wired they all sat at 0V, Should probably Insert C22 as well and see if they all remain at 0V.

After re-soldering C22 back in

C22
+ = 27V
- = 005mV-025mV

Depth
G=Bounces around from 005mV to about 030mV
H=0
F=0

Should mention also after re-soldering in the speed controls, all the pins there are 26.8V....is this right? or a symptom of the Q11,12 problem?

[lonewolf]

I think he means His hands on the board.. if the bulb is open(blown)it wont have continuity..is the bulb you replaced the same current/voltage rating?.a 20 year old meter is no problem as long as it is a decent brand..I use a meter Ive had since 1987 ...if you are going to keep swapping parts in/out put sockets in so you dont toast the traces..etc

[tr1p1n]

I think he means His hands on the board.. if the bulb is open(blown)it wont have continuity..is the bulb you replaced the same current/voltage rating?.a 20 year old meter is no problem as long as it is a decent brand..I use a meter Ive had since 1987 ...if you are going to keep swapping parts in/out put sockets in so you dont toast the traces..etc

Oh, would be nice, he'd have this thing working in a few hours as opposed with me taking a few weeks. Anyways, yeah the bulb is the same 12V/25ma.....at first it was a lot dimmer, but for some reason (after putting in C22, no idea what this would have to do with it) the bulb glows just as fine as the other one. Easily adjusted by the trimmer too and as for the sockets, yet to order them for the transistors. Q11 & 12 I've got easily removed/replaced (got the braid) as for the other soldering de-soldering, it's been actually relatively smooth. Just need to fix this current problem which is still very confusing to me. Everything seems OK but in all actuality it's not.

[R.G.]

Q13
C=19.54V
B=3.51V
E=2.92V

That's OK.

Bulb - Is there supposed to be continuity between the two bulb points? Might be a silly question, but just checking.
Depth side of the circuit = 26.9V
Opposite side = 19.64V

That's OK.

C23
+ = 3.55V
- = 0V sometimes I get 001mV, but 0 for the most part.

Depth
G=0
H=0
F=0

Those are OK too.

Coupled with the trimmer adjusting the bulb brightness, I think I was wrong - Q13 seems to be working OK.

Forgot one thing, Could not having the depth pot wired up give us these weird readings? Earlier when doing the tests I measured voltage without the depth pot wired and was getting 3.27V in H before slowly dropping, the others being 0V. Then of course after having it wired they all sat at 0V, Should probably Insert C22 as well and see if they all remain at 0V.

Yes, it could. The depth pot is what pulls the depth-pot-side of C22 and C23 to ground. Those pins not being at ground is what led me down the path of C22 and/or C23 being leaky or backwards.

After re-soldering C22 back in
C22
+ = 27V
- = 005mV-025mV

Depth
G=Bounces around from 005mV to about 030mV
H=0
F=0

Should mention also after re-soldering in the speed controls, all the pins there are 26.8V....is this right? or a symptom of the Q11,12 problem?

OK, this data leads me back to the LFO. The + end of C22 should definitely not be at nearly 27V. That's the voltage at the top end of the lamp and also the highest voltage in the thing.

If the board matches the schematic (that is, does not have additional shorts or opens it should not), then the only way C22's + side could be at that voltage is for Q12 to be shorted, or there to be a solder short or some such.

Pull Q12 out. Ensure that Speed and Depth pots are soldered in properly. Measure and report the voltages on the speed and depth pots and both ends of R40.

[tr1p1n]

Speed and Depth pots are all at 0V.

R40
Going to Q11 Base = 27.4V
Opposite Side = 16.04V

[R.G.]

Remove Q12 and Q11.
Repeat the measurements, and add the measurements on Q11/Q12 empty pads where the leads would solder.

[tr1p1n]

Remove Q12 and Q11.
Repeat the measurements, and add the measurements on Q11/Q12 empty pads where the leads would solder.

Depth & Speed all remain at 0V.

Q11
C=27.7V
B=002mV
E=002mV

Q12
C=27.7V
B=002mV
E=002mV

R40
To Q11 Base = 13.16V
Opposite Side = 16.13V

[R.G.]

Un power the board. Set your meter to read ohms and verify that the pads for the collectors of Q11 and Q12 show very low, almost zero ohms, to each other and to one side of the bulb.

Check the base pad of Q11 for resistance to Q11 collector, Q11 emitter, and Q12 base and emitter. All of these should show significant resistance, well over 1k ohms.

Check the emitter pad of Q11 for resistance to Q12 base (should be nearly zero), and to Q12 emitter (should be well over 1K).

If all that seems to be OK, put in a new transistor at Q11 and Q12 if you have them, not the old ones in case they have been damaged. If you have only 2N3904s, use them. If you have a higher gain transistor like a 2N5088, use it for Q11.

When this is done, check your soldering under magnification, power up and change to measuring Q11/Q12 voltages again. Post results back here.