Help debugging EZ Vibe

[MarkB]

OK
Just finished building an EZ Vibe..  and am getting no sound.

Here is what I've found so far.

All 4 opamps seem to be getting power OK.

The 2 LEDs at the bottom of the PCB are glowing.

The 4 LEDs that should be flashing - are not... and seem to be getting no power at all..

So what sounds like the obvious place to start here?
"-)

[MarkB]

anybody have some voltage measurements from theirs?

I have a sneaking suspicion that it's something simple and stupid and I was overlooking it because it was 2am.
"-)

[R.G.]

What really matters are the voltage readings from yours.

[MarkB]

Another addition..

Using an audio probe.. I have signal through all 4 opamps - and I can get SOME signal at one side of the LDRs.

It's looking more and more like the flashing LEDs are the culprit here...

but why, oh why aren't they flashing!?
"-)

[MarkB]

What points are the key places to measure, RG?
I've got it right here in front of me.
"-)

[MarkB]

here come the voltages... measured ICs first.

All measurements in V unless otherwise noted

U1 Pin voltage
1 - 3.87
2 - 3.87
3 - 2.0
4 - .6mv
5 - 3.78
6 - 3.87
7 - 3.88
8 - 9.2

U2 Pin voltage
1 - having a hard time measuring... won't lock in - flashing different Vs
2 - 3.87
3 - 3.87
4 - .5mv
5 - 3.6
6 - 3.87
7 - 3.87
8 - 9.2

U3 Pin voltage
1 - same as U2  [edit - now measuring 2.17]
2 - same as pin 1 [edit - now measuring 2.17]
3 - same as pin 1
4 - .5mv
5 - 3.67
6 - 3.87
7 - 3.87
8 - 9.2

U4 Pin voltage
1 - same as U2/U3
2 - 3.86
3 - same as pin 1
4 - .4mv
5 - 3.72
6 - 3.86
7 - 3.85
8 - 9.2

I'm getting pretty much nothing on the 'flashing' LEDs

R18 after the DRIVE pot cranked is 2.17V and .7mV after R18

[Pablo]

Mark,

when i built mine way back when John first put this on the web
i read the 220R as 220k and had a very similar problem.
when i put the 220 ohm in there all was well.  
you might want to double check the value of that resistor (R18)

[MarkB]

Thanks for the reply..
I just looked, double checked, and re-measured, and R18 is definitely a 220-ohm..

I'm still holding out hope that it's something simple like that.

It seems that the LEDs aren't getting their proper voltage... I'm looking at the schematic and RG's layout - and I'm trying to figure out what could be causing that..
"-)

[smoguzbenjamin]

You can't measure any voltage drop over the LEDs? Then I'd say trace back to the PS untill you find the place where it's malfunctioning... :?

[MarkB]

the LEDs are hardly getting any voltage.. gotta find what's going on..
[edit]
OK - so at Alfonso's suggestion - I lifted R18 (the 220 before the LEDs) and now I can measure the LFO..  as soon as I hook it up to the LEDs, it stops oscillating and gives me a wierd reading.

So something is wrong with the LEDs.. any idea what would cause that behavior?

Also - in circuit, I can measure the voltage across the diodes BOTH ways.. which it shouldn't do...  so - we're narrowing it down now..
"-)

[MarkB]

OK - one more question, and I'll stop bothering everyone..

I got the LEDS flashing.. it was a short, and it's fixed.. all are now flashing properly.. YAY!

NOW - I have two problems, probably related.

1. the 1uF cap at the output is not letting the signal pass... using an audio probe - I can hear it at the + leg, but nothing at the - side..

2. the dry signal is MUCH louder than the effected signal.. the effect is there, but it's VERY quiet.. if I switch to 'vibrato' mode (all effect) it's definitely warbling and vibratoing..  but VERY quietly..  any obvious places to look for that?

Thanks again!!
"-)

[Gearbuilder]

Hi,
I've got the same constatation about the output volume of this effect,for the coupling cap, i think it could be resolved by changing the cap.
Regards
Bruno

[MarkB]

Thanks - I'll swap the cap..
the effect level is VERY quiet.. so the 'chorus' mode sounds like there's almost no effect going on - because it's mixed in VERY low against the clean signal.
"-)

[MarkB]

ok - I realize that I post more on my own debugging thread than everyone else, but I'm really working on this thing!

OK - I've traced it to where it seems that the effect is working normally - about the same volume as the output of U1 (clean signal) - but then I get a huge volume drop across R13 - right before the Chorus/Vibe switch..

any idea what would cause such a HUGE volume drop there?

If I listen to the output of U4, right before R13, it sounds nicely effected... but the volume drops there - so when it's blended with the clean signal - it's so quiet I only hear clean.

Also - can anyone give me a voltage measurement off the 220 that drives the LEDs? (LFO output).. mine is swinging from a little under 3v to a little over 4v - does this sound right?

Getting close!!
"-)

[MarkB]

OK - I realize I keep replying to myself... but I'm starting to pull hair now..

Ever feel SO close, yet be SO far away?

I swapped out C6 - the output cap - but it still won't pass audio!  I can hear sound on the + leg of it with an audio probe, but nothing at the output.

Also can't figure out for the life of me why the effected signal is being cut so much.

Anyone who's built an EZvibe - can you take some measurements, etc?

"-)