Tri-Vibe Debugging - help please ?

[Stormbringer]

Hi All

Newbie here - and 1st post so be gentle - lol 

After spending lots of time lurking here and learning loads (thanks to you all !!) I decided to build a Tri Vibe using Slacker's vero layout.
Problem is now I have built it I am having a few errr teething problems.....and wondered if anyone would be kind enough to maybe give me a few pointers
for my troubleshooting ?
Following the What to do when it doesn't work thread has yeilded the following information.

Details are :-
Schematic here http://runoffgroove.com/tri-vibe.html
Layout here http://www.aronnelson.com/gallery/main.php/v/slackers-stuff/trivibeboardfinal.jpg.html?g2_imageViewsIndex=1

Firstly my thanks to the people who gave their time and effort to come up with the effect at ROG and to Slacker for his vero layout which enabled me to build this. Cheers 

I followed the vero layout exactly (to the best of my knowledge!). I marked stuff off as I fitted it and used a DMM to check values as well as colour codes.
I only made two parts substitutions - I used a 1nf mylar capacitor as I couldn't get a 1n5 at the local Maplin where I got most of my stuff from (what issues would that cause please?) and I only had a 470k Lin pot which I used just to get up and running - will that be ok, just a bit bunched up ??

It is temporarily wired into a test box that has just stereo in and mono out jacks, and a battery.

When plugged into my amp I get the following:-
Mode 1 - very quiet signal to amp - no effect evident. Distorts on the attack of the notes if a chord is strummed hard.
Mode 2 - nothing
Mode 3 - nothing
The LED on the board glows but is only dim (correct I believe?)

I have double checked for wiring errors and used a good magnifying glass to look for solder bridges and other soldering issues but I cannot see any.....
I also got my son to use his younger eyes lol - but he also found nothing obvious.....

I have read as many other threads for the tri-vibe as I can find and have compared my voltages to others I have found.
Here are my voltages. I know some are very weird but am struggling to see why from the schematic and the layout.
Any help with this bit would be really really helpful - Ta..

U1 - TL072 (socketed)

1. 4.32
2. 4,32
3. 3.48
4. 0
5. 4.31
6. 4.31
7. 4.31
8. 8.6
I think this one is OK?

U2 - LM13700 (socketed)

1. 0.683 *
2. 5.13
3. 4.46
4. 4.45
5. 0.01 *
6. 0
7. 0.06 *
8. 2.14 *
9. 1.43 *
10. 0.01 *
11. 8.58
12. 0.1 *
13. 4.3
14. 4.41
15. 5.05
16. 0.68 *

The ones marked with a * are the ones I believe are way off ! Could anyone tell me if there is a particular place to be looking for the
reason for theses low voltages please ? I have checked the components a couple of times now and am pretty sure they are right - but the voltages suggest different?

U 3 TL064 (soldered to board  - ran out of sockets)

1. 0.681 *
2. 8.22 *  I have spent ages trying to find out why this is not 4.3V ish. Any clues please ?
3. 4.29
4. 8.56
5. 4.27
6. 4.29
7. 4.29
8. 4.96
9. 4.29
10. 4.29
11. 0
12. 4.29
13. 4.24
14. 4.24

There does not seem to be any occillation on any of these voltages. I have checked them a good few times and they are always the same ( I hoped it would 'heal' itself !! lol  )

Sorry about the long read - I just wanted to give as much info as I could to help you to help me!
I think one issue that is confusing me when troubleshooting is the different chips between the schem and vero (TL062 / TL 064) and the way they are laid out
I can't seem to get the pin ins and outs connected in my brain 

All suggestions much appreciated - especially the what to do next ones.
Cheers
Stormbringer 

[PRR]

IC and pin numbers are _different_ from schematic to layout.

I don't want to whine, but I'm getting lost around layout's TL064 trying to match to the schematic's TL072.

The symptoms match the idea that the LM13700's internal nodes 5,7 10,12 are stuck low which suggests the LM13700 sections are turned "off". No audio passes, except the dry sneak path in "swirl" mode.

Can you turn "Depth" to get ~~4.5V on its wiper?

Can you find pin the "LFO" line? It may come off layout's pin 1 IC3.

Short layout's R37. Do you now have ~~4.5V on "LFO" line? Does signal pass through the LM13700 stages?

[Stormbringer]

IC and pin numbers are _different_ from schematic to layout.

I don't want to whine, but I'm getting lost around layout's TL064 trying to match to the schematic's TL072.

The symptoms match the idea that the LM13700's internal nodes 5,7 10,12 are stuck low which suggests the LM13700 sections are turned "off". No audio passes, except the dry sneak path in "swirl" mode.

Can you turn "Depth" to get ~~4.5V on its wiper?

Can you find pin the "LFO" line? It may come off layout's pin 1 IC3.

Short layout's R37. Do you now have ~~4.5V on "LFO" line? Does signal pass through the LM13700 stages?

Hi PRR
A big thanks for the help 
I think that Slacker substituted an 064 for two 062s for layout reasons. Here is a comment from him from the original thread
' I used a TL064 instead of a pair of TL062s because it made the layout a bit simpler, note that it's upside down compared to the other ICs.'

I am not too sure about the upside down bit - I was guessing that he meant the u2a and b and U3 a and b from the schematic were reversed but I'm not sure and this is making my troubleshoot harder as you say ....
Thanks for your comments on the LM13700 ....it is as if it is off. Makes a bit more sense to me now ! I havent progressed any with this bit up to now though.

The depth pot has 4.4V (or there abouts) on all of the terminals. This doesn't change with wiper position though . a clue maybe ?

Assuming that pin 1 IC3 is the LFO line as you mentioned (I will do more checking tomorrow - a bit late here now ! )
(From another Trivibe vero debug thread : The voltage on both pins 1 and 16 of the LM13700 should also vary a little.
I measure about 1.24. ~ 1.37V)

I shorted R37 and that moved pins 1 and 2 of the IC3 ( TL064 in my case) to 4.3v each ! Does that help at all ? I'm sure it tells me something but not sure what !
I will have to check if the audio signal passes through tomorrow I'm afraid - it's 2am here now !! I will also see if that short has changed any of the voltages around the LM13700 while I'm at it ...

Many thanks again
Stormbringer 

[PRR]

Un-short R37. Lift one end of R33 R34 and R36. These parts are to un-kink the waveform. They are needed for best sound but it will vibe without them... if there is a mis-wire in this area forcing "LFO" low, maybe taking the frills out will get it vibing, then re-connecing 1-by-1 may narrow the problem.

> The voltage on both pins 1 and 16 of the LM13700 should also vary a little.
I measure about 1.24. ~ 1.37V)

That voltage will vary VERY little, is not a great clue, and is the one place where a careless probe WILL blow the IC. Leave these pins alone. The real parameter is the current in the 10K resistors connected to these pins, i.e. the voltage on the LFO line which is the top stripe on that layout. This voltage needs to be a volt or more above zero but less than 10V. In this case, probably centered on 4.5V or so and wobbling with Depth toward 2V to 7V (maybe too fast for your DMM to follow). Until LFO line is up at several volts the '13700 is not gonna be happy.

[Stormbringer]

Thanks again for the help PRR - much appreciated.

Just to clear up the remaining shorting of R37 question - tried it with a guitar signal today and it made no difference at all to passing audio.

I will now try your next suggestion of lifting the pins on the resistors you identified and see what that gives me.
I might not be able to do that until tomorrow though  but will post the results when I do .......

Thanks for the warning about the pins on the '13700 - I shall leave them alone !

I have also spent some more time trying to work out how this circuit works - progress is slow though !!

Stormbringer

[Stormbringer]

OK - Further update - and much better news I think !!

Thanks to your suggestions I have just discovered a wrong value resistor -  - A little embarrassed would cover it lol !

R33 was 270 ohm instead of 270Kohm.... I assume that this would be enough to cause problems !?
I pulled one leg of R34 and checked LFO rail voltage - no change
I pulled one leg of R33 and checked LFO rail voltage - now up at 4.2V from 0.86V !! Tested the resistor and found the mistake - Do'h...

I won't have chance to check what happens with the audio until tomorrow - but it feels like, thanks to your direction, I have made some progress !

Would you recommend still removing one leg of R36? Its definately the right value (68Kohm)
What about replacing the leg on R34 and replacing R33 with the correct value - or should I wait until I have tested with an audio signal ?
Thanks again for your help PRR - seriously appreciated 

S

[PRR]

> 270 ohm instead of 270Kohm.... I assume that this would be enough to cause problems !?

I hire you and promise you $270,000.

When time to pay, I only give you $270.

Yeah, makes a difference.

So much that it may be the entire problem.

[Stormbringer]

Hahaha - well made point there !! 

Thanks

OK - Another update
Replaced R33 with the correct value, and put the pin on R34 back down.
Now seeing 4.3V on the LFO rail (top on layout) - much better.

Tried with the guitar - Much better in terms of clarity and output level but very little in terms of effect.
Also - still only getting an output on Swirl setting. Still nothing on position 2 or 3 ...

I have checked the pots for variation in resistance when turning them and they seem OK
I have checked the continuity across the switch (at the board connections) and that also apprears to be correct.

I am going to have to spend some time checking component values again I think - based on finding one wrong one already !

Any further help in diagnosing this now would still be very much appreciated though !!

I have a feeling It may be a good time to build and use an audio probe ??

Thanks for the help up to now PRR

Regards
Stormbringer

[PRR]

> It may be a good time to build and use an audio probe ??

Yeah.

You could go as simple as a 0.1u cap on the end of a cut guitar cord, into a practice amp. All the audio levels here are nearly guitar-level, but you do need to block the DC.