Neo Vibe Debug

[slim_chiply]

I just recently built a Neo Vibe from a pcb from GGG.  It pretty much worked when I was done, but was really noisy.  There was rf interference and I could hear the lamp oscillating.  Apparently, I ordered the wrong gauge wire for the pots, jack, and etc... because it kept breaking at the solder joints.  Thinking that this couldn't be helping my noise problems, picked up some heavier gauge wire and re-wired everything.  After the re-wire, the lamp would no longer oscillate.  It will light up if I use a power supply (I've tried 2 24vdc 500ma and a 16vac).  However, if I use 2 9v batteries in serial, the lamp won't light.  I've checked and double checked the re-wire part and I don't see any thing wire wrong.  Though I have to admit I did make a couple mistakes.  It all looks good to me now.

There is another issue that is making the whole debugg process more difficult.  I'm having serious overheating issues.  C18, Q11, Q12, and Q13 all get too hot too really touch and if I leave the pedal plugged in more than a few minutes it will start to smoke.  I've replaced these parts, but the issue is probably someplace else.  I've been over the pcb with a magnifying glass and don't see any shorts.  I've remelted all the solder joints.  After I re-wired the pedal. I accidently shorted something and there were sparks a couple of times.  I'm guessing that I fried something, but I'm not exactly sure where to start.  The voltages I've measured seem ok compared to others I've seen on this forum

I measured the transistor voltages with the 2 9v batteries since that set-up doesn't seem to cause the serious heat problem. 

I appreciate any help that anyone can provide.

Doug

Here's the voltages I measured:
Battery 16.5 V
78L15 In 16.3 Out 14.9

	c	b	e
Q1	1.71	0.81	0.94
Q2	4.10	1.71	1.47
Q3	10.63	6.37	3.56
Q4	14.38	4.04	4.09
Q5	10.80	4.04	3.52
Q6	14.37	4.05	4.10
Q7	10.73	4.09	3.54
Q8	14.38	4.02	4.06
Q9	10.86	4.06	3.48
Q10	14.37	5.11	5.18
Q11	15.75	11.81	15.74
Q12	15.74	15.74	15.72
Q13	13.33	2.05	1.36

[slim_chiply]

No one has any useful advice?  Short of replacing each component one by one I'm not sure what's next.  I can do ok on solder part.  The desolder is another story.


Thanks,

Slim

[R.G.]

You have/had a number of things going on.

It pretty much worked when I was done, but was really noisy.  There was rf interference and I could hear the lamp oscillating.

This is almost certainly a grounding and/or shielding problem. You did mention that you had corrected some wiring problems, which probably will/did take care of this.

Apparently, I ordered the wrong gauge wire for the pots, jack, and etc... because it kept breaking at the solder joints.

Wrong gauge wire doesn't cause breaking at solder joints. Nicking the copper wire when stripping off the insulation DOES cause it to break at the solder joints.

Thinking that this couldn't be helping my noise problems, picked up some heavier gauge wire and re-wired everything.  After the re-wire, the lamp would no longer oscillate.

... indicating a wiring problem re-introduced, perhaps.

It will light up if I use a power supply (I've tried 2 24vdc 500ma and a 16vac).  However, if I use 2 9v batteries in serial, the lamp won't light.  I've checked and double checked the re-wire part and I don't see any thing wire wrong.  Though I have to admit I did make a couple mistakes.  It all looks good to me now.

9V batteries have problems supplying enough current for a light bulb. If they're not perfectly fresh, they probably can't. But the substitution of power supplies can cause other problems.

There is another issue that is making the whole debugg process more difficult.  I'm having serious overheating issues.  C18, Q11, Q12, and Q13 all get too hot too really touch and if I leave the pedal plugged in more than a few minutes it will start to smoke.

... not the least of which is that you can reverse the polarity of capacitors and transistors and damage them. After that, they may get hot.

I've replaced these parts, but the issue is probably someplace else.  I've been over the pcb with a magnifying glass and don't see any shorts.  I've remelted all the solder joints.  After I re-wired the pedal. I accidently shorted something and there were sparks a couple of times.  I'm guessing that I fried something, but I'm not exactly sure where to start.  The voltages I've measured seem ok compared to others I've seen on this forum

Yep, that could cause some damage too.

I measured the transistor voltages with the 2 9v batteries since that set-up doesn't seem to cause the serious heat problem. 

My best guess at this point is that the power supply tinkering and wiring issues have caused one or more electrolytic capacitors to be reverse biased and damaged. Check the voltages across the electro caps and post them back here.

[slim_chiply]

First off.  Thanks for offering to help.  It is greatly appreciated.  There was a bunch of useful information in your post.  I chucked the old wire cutters for newer sharper ones and an actual wire stripper.  That should take care of the wire breaking on me (I hope).

I did my best to measure the capacitor values, but is was a first for me, so if they look really odd it could be multimeter user error. 

Here the capacitor values I got.

Thanks again for your help.

Slim


   
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      

C1	.80
C2	-1.5
C3	-12.75
C4	4.27
C5	-5.55
C6	.85
C7	.98
C8	.84
C9	-5.6
C10	1.04
C11	.88
C12	-5.62
C13	1.04
C14	2.00
C15	-4.5
C16	.62
C17	4.64
C18	2.2
C19	-1.04
C20	-.12
C21	14.8
C22	2.2
C23	4.8
C24	15.69
C25	15.71

[R.G.]

Sorry - I didn't tell you the whole story, I guess. I need the voltages with the red/positive probe on the side of the cap marked "+" and the black/negative probe on the side of the cap marked "-". I was trying to find out if any caps were shorted, which would cause the voltages to be zero, but also whether the voltage was reversed on any cap, and I need the measurement with respect to the capacitor marking to tell if it's reversed.

[slim_chiply]

R.G.,

Thanks for all of your help.  There were a couple caps that were bad (C1 and C2 only I think, I end up replacing a couple others though).  That seems to have taken care of the heat problem.  I let it run for a while and Q13 is a little warm but not burning to the touch.

I also learned another important lesson.  After you've  verified the wiring a coule times and determined that is not the problem.  You should probably check it again and perhaps again.  I had the depth pot wired backwards.  Argh!  That is fixed and the lamp is flashing as it should.

So pretty much everything is working.  I still have some hiss and a little breakup if I play really hard though and I can faintly hear the lamp pulsing in the single.  It's an old timey thing so perhaps I'm being a fussy.  I don't know how quiet it should be. 

I've built a couple pedals from kits and this was my first from a pcb.  I did a poor job of spacing the holes for the case.  Everything is crammed in there.  I'm sure that can't help. 

I need to re-drill and paint the case (bondo the mis-drills).  When I do that I'll reflow all the joints.  I've mucked up a few and get a magnifying glass to make sure the pcb is as clean as possible.  I'll see if that clears up the hiss and the break ups.

Thanks again for your help,

Slim

[R.G.]

Hey! Congratulations! You got it going!

Hiss should not be too bad. There is a little in any setup with so many transistors and resistors, but that's not a common complaint. I guess the right description is unusual but not unheard of. Pulsing with the light is probably a voltage sag problem. Are you driving the bulb from voltage before or after the regulator?

[slim_chiply]

I'll have to double check, but I'm guessing after.  I used a GGG pcb and wired it up as indicated.  I'm very slow at tracing a schematic so it will take some time to actually figure that out for sure.   I may need to tweak the lamp pot a little too.  I may have it too bright.  I like the sound a bit more subtle.  I was just happy to have it working again.

The hiss isn't too bad.  I have worse.  I have an Ibanez flanger/chorus that has a digital hiss that is like fingernails on a chalkboard to me.  This one at least sounds natural.