NeoVibe Debug, part II, Voltages.

[sjaltenb]

Symptoms: No sound, very very dim bulb (although if i short the driver B/C i get full brightness). No control over bulb.

Mods: Powered via external filtered 9v and Charge pump as advised by R.G. Power is inputted into filter cap 2, with ground and 15V regulated power coming in, being powered temporarily by a 1 Spot.

Voltages:

Q1: C 2.4
     B 1.4
     E1.03

Q2: C 4.4
     B2.1
     E1.5

Q3: C 11,8
     B4.5
     E3.8

Q4: C 15.13
     B 4.7
     E 4.3

Q5: C 11.45
     B4.3
     E 3.7

Q6: C 15.13
     B 4.7
     E 4.3

Q7: C 11.5
     B 4.3
     E 4.7

Q8: C 15.13
     B 4.7
     E 4.3

Q9: C 11.5
     B 4.3
     E 3.6

Q10: C 15.13
       B 5.8
       E 5.3

Q11: C15.14
      B 6.7
      E 7.7

Q12: C 15.13
       B 8.3
       E 7.7

Driver: C 13.5
          B 1.6
          E .9

Lamp: 15.3 on the supply side and 13.5 on the driver side. I am also getting Zero ohms from the Emitter of the driver and Ground, but not continuity.

EDIT: bad news, i think i smelled/saw some smoke while i was tinkering. What components would blow up??? I'm going to start with all the electrolytics, since I have them in stock anyway.

[zeeman]

Symptoms: No sound, very very dim bulb (although if i short the driver B/C i get full brightness). No control over bulb.

The first question I have is... what layout/PCB are you using?

Mods: Powered via external filtered 9v and Charge pump...

Hmmm... I am very tired right now (sigh...) so I may not be thinking straight.

What charge pump are you using?

If I recall correctly, the MAX1044 can only supply around 10mA of current and the 1054LT can only supply around 100mA.

I don't think either of these ICs can supply enough current for a Univibe/Neovibe.

EDIT: bad news, i think i smelled/saw some smoke while i was tinkering. What components would blow up???

I guess that kind of depends on where you where you were tinkering when the smell/smoke occurred.(?)

zeeman

[sjaltenb]

Hmmm I did not think about the issue with the charge pump and current. Are you sure it will only supply 10ma? I can get the bulb to full brightness, i just have to touch the B/E of the bulb driver. If it were not supplying enough current, would this be possible? I'll do some research on the MAX1044.

Wouldn't I be able to tell based on voltages if a transistor blew up? They are all still the same. It may have been the soldering iron smoking a bit, but it sure had a different smell.

The Layout is the same as the GeoFX, (the original R.G. layout). This is the bulb: 12V, 40ma:

http://www.smallbearelec.com/Detail.bok?no=716

[R.G.]

Symptoms: No sound, very very dim bulb (although if i short the driver B/C i get full brightness). No control over bulb.

That probably means the problem is in the drive to the bulb driver. Shorting B/C would not change it at all if the transistor was bad.

Note that in measuring voltages, you need to measure the base-emitter voltages directly on the base-emitter for Q1, Q4, Q6, Q8 and possibly Q10 because the input impedance on the bases is so high that the meter impedance can pull down the base while measuring.

Q1: C 2.4
     B 1.4
     E1.03

Seems OK, based on the note about high impedances on bases.

Q2: C 4.4
     B2.1
     E1.5

Q3: C 11,8
     B4.5
     E3.8

Q4: C 15.13
     B 4.7
     E 4.3

Q5: C 11.45
     B4.3
     E 3.7

Q6: C 15.13
     B 4.7
     E 4.3

All these look OK, given the note on high base impedance.

Q7: C 11.5
     B 4.3
     E 4.7

This looks wrong for B and E, but the C is OK. Did you transpose the measurements while typing?

Q8: C 15.13
     B 4.7
     E 4.3

Q9: C 11.5
     B 4.3
     E 3.6
Q10: C 15.13
       B 5.8
       E 5.3

No obvious problem here.

Q11: C15.14
      B 6.7
      E 7.7

This one is very strange. Could be the high base impedance problem.

Q12: C 15.13
       B 8.3
       E 7.7

Very odd. Q12 base should be at the same voltage as Q11 emitter, they're supposed to be connected by a wire.

Driver: C 13.5
          B 1.6
          E .9

No obvious problem. I think the issue is with Q11/Q12.

I am also getting Zero ohms from the Emitter of the driver and Ground, but not continuity.

I believe that's a meter/measurement technique issue. Your meter may not beep for continuity, and may not be able to truly show low ohms. Verify the path by inspection.

EDIT: bad news, i think i smelled/saw some smoke while i was tinkering. What components would blow up??? I'm going to start with all the electrolytics, since I have them in stock anyway.

I believe that's a wiring problem/fault, not a failing capacitor issue. Check whether your charge pump is getting hot.

Hmmm I did not think about the issue with the charge pump and current. Are you sure it will only supply 10ma? I can get the bulb to full brightness, i just have to touch the B/E of the bulb driver. If it were not supplying enough current, would this be possible? I'll do some research on the MAX1044.

Charge pumps are funny things. Some pumps have a current limit, but the simple ones like the MAX1044 do not. They simply sag under load. A switched capacitor can be modeled as a resistor. In the case of the 1044, that's about 80 ohms. This varies with the switching frequency and the value of the capacitor.

Wouldn't I be able to tell based on voltages if a transistor blew up? They are all still the same.

It may have been the soldering iron smoking a bit, but it sure had a different smell.

You may have touched some new kind of plastic with the iron.

[sjaltenb]

R.G. can't thank you enough for your generosity. You've helped me a great deal over the years! But i am learning! I went ahead and re-tested each Q. Also, i have visually inspected EVERYTHING!! 10x at least, and resoldered, etc, but I will keep at it!

Charge pump barely putting off any heat. I get steady 15.12 volts out of the regulator, even if the bulb is fully on, So i think the pump is capable of supplying enough current. At least, as far as reasonable thinking would tell me.

Q1: C 2.135
      B 1.45
      E 1.04

Q2: C 4.45
     B 2.13
     E 1.56

Q3: C 11.07
     B 4.46
     E 3.89

Q4: C 15.13
     B 4.73
     E 4.3

Q5: C 11.44
     B 4.3
     E 3.7

Q6: C 15.12
     B 4.7
     E 4.3

Q7: C 11.5
     B 4.3
     E 3.65

Q8: C 15.13
     B 4.73
     E 4.26

Q9: C 11.55
     B 4.26
     E 3.6

Replaced Q10 with another 2n5088, just in case:

Q10: C 15.13
       B 5.88
       E 5.38

Q11: C15.14
      B 7.24 - although hard to get a steady reading
      E 8.26

Q12: C 15.13
       B 8.26
       E 7.67

Driver: C 13.6
          B 1.603
          E .9

[R.G.]

R.G. can't thank you enough for your generosity. You've helped me a great deal over the years! But i am learning! I went ahead and re-tested each Q. Also, i have visually inspected EVERYTHING!! 10x at least, and resoldered, etc, but I will keep at it!

You're welcome to any help I can provide.

Charge pump barely putting off any heat. I get steady 15.12 volts out of the regulator, even if the bulb is fully on, So i think the pump is capable of supplying enough current. At least, as far as reasonable thinking would tell me.

Actually, I think you may be the first person to actually test this setup. It's very good to know it works. If you're getting a steady 15V out of the regulator, and the charge pump isn't overheating, you're golden. Frankly, this is good enough news that it needs to get noticed and maybe even incorporated into the PCB. Powering the 'vibes is a big enough pain that having a good way to pipe in 9V and just have them work is a big deal.

If you don't mind, as you go through the rest of the debugging, could you possibly splice your meter into the + lead and measure the actual current drain? I've modelled it and calculated it, but I don't have a working vibe to measure at the moment.

Actually, all those except Q11 look fine, and I think Q11 is probably fine, just hard to measure. Can you do some audio probe tracing through Q1-Q10?

[sjaltenb]

Well hey, maybe I can actually provide some insight for once!

Sure, I will get those current measurements as soon as I can. Although I have never measured current before, so it may take a little lesson.  

I will go back and really really inspect everything around Q11, and also get the audio probe out. I am guessing that the signal path goes from Q1-10....and 11,12 have to do with the lamp, not the signal.

I still can't figure out why the bloody thing won't light up or respond to to any changes in speed/depth. It did before...and it shouldn't have to do with the power.

It will probably be next week before I can get down to this. I have job interviews which, because i have no future in guitar pedal building, comes wayyyyy before my neovibe debug. Unless you are sooooo curious about this little setup that you want me to send it to you R.G.  

[R.G.]

Well hey, maybe I can actually provide some insight for once!
Sure, I will get those current measurements as soon as I can. Although I have never measured current before, so it may take a little lesson.  

It will be appreciated, and will be a contribution to anyone who's thinking about doing a Neovibe. I was surprised that it worked, but hey, I'll take it. 

I will go back and really really inspect everything around Q11, and also get the audio probe out. I am guessing that the signal path goes from Q1-10....and 11,12 have to do with the lamp, not the signal.

Yes - signal runs through Q1...Q10. Q11 and Q12 are the LFO which makes the modulation that the driver transistor puts on the bulb.

I still can't figure out why the bloody thing won't light up or respond to to any changes in speed/depth. It did before...and it shouldn't have to do with the power.

It's probably something simple - broken wire, bad solder, bent component lead, something like that. Since it worked once, it will work again. If the power is a steady 15V or so, not sagging down under 15, it's probably not a power supply problem as such.


It will probably be next week before I can get down to this. I have job interviews which, because i have no future in guitar pedal building, comes wayyyyy before my neovibe debug. Unless you are sooooo curious about this little setup that you want me to send it to you R.G.  

[sjaltenb]

OK so i hooked up the NeoVibe this morning to my test rig and voila, sound!

Perfect vibey floydish trippy sound....IF i use my hand to create the lfo  

The bulb still isn't flashing or changing at all, it is stick on very dim with no fluctuation. but the good news is that the signal is passing clearly and the modulation is working perfectly, i just need to get the bulb to flash. I replaced Q11, same voltages, nothing happened.

What could be going on here...any ideas? I will hunt around...for the 30th time for a problem in the circuit.

[R.G.]

OK so i hooked up the NeoVibe this morning to my test rig and voila, sound!

Perfect vibey floydish trippy sound....IF i use my hand to create the lfo  

The bulb still isn't flashing or changing at all, it is stick on very dim with no fluctuation. but the good news is that the signal is passing clearly and the modulation is working perfectly, i just need to get the bulb to flash. I replaced Q11, same voltages, nothing happened.

What could be going on here...any ideas? I will hunt around...for the 30th time for a problem in the circuit.

You have done a good application of "divide and conquer". You've found that the audio portion is working fine, so that leaves only the LFO and lamp driver to figure out. We've figured out lamp drivers many times here.

There are only a few possibilities remaining:
- the LFO may not be oscillating
- the LFO may be oscillating but the signal is not getting to the lamp driver through the depth pot and wiring
- the signal may be getting to the lamp driver but the lamp driver is not driving the lamp properly.

My first step if I had it here on my bench would be to - yep, measure all the DC voltages on the transistors very carefully again. I would also add measuring the DC voltages on the string of three capacitors in the LFO, and the DC voltages on the depth pot. For Q11, you'll need to measure from base to emitter instead of base to ground because of the very high impedance there.

[sjaltenb]

Success!!!

Sorry I could not catch you before you posted R.G....

I am not sure what I did. Honestly, and you will not believe this, I got frustrated and started poking around with a screwdriver. Well, the bulb turned on and the controls started to work.

The only issues I can find are thus: the driver trimmer is turned all the way down (zero ohms) and that is the only way I get decent light from the bulb. I have heard some people have to use a 500ohm trimmer, so this leads me to believe that something is wrong, and that I should have more range.

The tone is pretty good. I don't have a proper light shield, but using a copper tape 'box' i had previously made, with the lights off, it sounds good. The only thing i notice is that the 'turn' is very hard. Almost instead of being a smooth motion from on to off, it is very heartbeat like. ON OFF ON OFF instead of onnnnnnnofffffffffonnnnnnnoffff. Should the bulb not light up as much on the slower settings, i thought it should only control the speed, not the brightness/intensity. Maybe they are interrelated. That and a nice buzz, but it is not in an enlcosure yet.

Pretty terrible description, i know But oh, it is soo dirty and vintagey.

But anyway, I HAVE A WORKING NEOVIBE! Thanks so much for all your help R.G.
Hope that makes sense.