Toney vero Ross comp build...works...sort of

[m-theory]

I got this build put together the other day, plugged it in to try it, and found that I could only get it to work when I applied just the right amount of finger pressure to just the right spot on the circuit.  Not terribly practical for use on stage. 

Since this is a vero build, it seems that all I can do in order to debug is to carefully check my solder connections and the trace breaks, which I've done.  At this point, I'm on the verge of scrapping it and starting over, and just biting the bullet on ordering a PCB. 

One question that I'd like answered is, does the output of the circuit come from lug 2 on the volume pot, as it would appear? 

Second, is there any viable way to go about debugging this that would offer a reasonable potential for success?  It seems a shame to go through all of this work and be SO close to having a successful build, and then end up tossing it away because I'm unable to make it work properly. 

http://aronnelson.com/gallery/Toneys-Album/Rossv4?full=1

[calculating_infinity]

Hey there,
     Yeah lug 2 should go to out.  As far as debugging goes http://www.diystompboxes.com/wiki/index.php?title=Debugging .  In there is also a link to R.G.'s debugging page.  With an audio probe debugging gets A LOT easier.  Multimeter is essential as well.  For me, I avoid larger vero builds and try to get a pcb.  Not to say that you shouldn't try and debug your comp.  I actually was having problems with my ross comp a couple weeks ago and was going to trash it but successfully debugged it using the techniques in the aforementioned link.  Good luck man! 

-Jonathan

[m-theory]

Thanks.  I'll give it another shot.  This is one of those that would be a real morale boost if I succeeded, but I'm really not holding my breath.  I'm pretty much considering it recycle material at this point. 

[calculating_infinity]

'Well I hope you are successful in debugging it!  Audio probe is actually really cool as you will learn more about the circuit when you probe it.  I am fortunate to have enough parts laying around so that when my Ross Comp wasn't working, I was still able to build other projects.  I do encourage you to get the bugger working just for self satisfaction.  However if you dont Mark M has some great comp layouts!  Well again, good luck man.  I feel for ya!

-Jonathan

[Jay Doyle]

Your problem screams a cold solder joint or other solder problem.

Resolder every connection (starting around where you apply your finger pressure to make it work) by heating up the joint and letting a little more solder flow onto it.

Do that first, then post the voltages and we can help you more. I don't have enough info to really work out what is wrong.

DO NOT throw this out, we can get it working for you. Read the 'What to do if it doesn't work' sticky on the top of the bulletin board, follow the instructions and then post back...

Jay Doyle

[m-theory]

Thanks Jay.  I think I've figured this problem out, but won't know for certain until this evening.  At the very least, I've got to be very close to having it working, because it works when the right pressure is applied in the right place. 

Last night, I re-visited the build, after setting it aside for a few days.  I really focused on where the issue seemed to be, and determined it to be the trimpot.  Upon closer examination, I found that one of the leads on the trimpot wasn't connected at all.

When I went after it with the iron, I remembered that I'd had an issue with this when I installed.  The pot was defective, and that particular lead was very short, and wouldn't reach through the hole, so I made a "drop solder" attempt.  I attempted the same feat again, plugged in again, no go again, found the same issue again. 

I then soldered tiny lengths of wire to the leads, and soldered them into place on the board, plugged in, and tried again.  Again, it failed, and when I looked underneath, the strip on the vero board was peeling off, so I soldered a jumper wire there and tried again.  Again, it failed, and this time when I examined it, I found that the wiper lead had snapped completely off at the base of the pot, so it's junk.  It's almost as if the damn thing has a mind of its own, and just refuses to work properly!

This evening, I'll try putting 2-1k resistors in place of the 2k trimmer, and we'll see what happens.  If that fails, I'll take some readings.  Thanks again.

[Jay Doyle]

The two 1ks should do it. That is your problem. Don't trash it just because you burned off a trace either. You've put a lot into this and you are REALLY close to having it right, if anything set it aside, order another 2k and wait...

[m-theory]

Well, the trimmer apparently wasn't my only problem.  That didn't solve my problem.  It still does pretty much the same thing, although I don't really have to apply pressure on the circuit anymore, but rather just moisten a finger and place it in the same general area on the circuit.  I'm acting as a conduit to complete some portion of the circuit that apparently isn't quite right. 

I'm going to step back for a bit, collect my thoughts, and then start poking around to take some measurements, and I'll come back to re-post when I've gathered up some numbers. 

Thanks again.

[m-theory]

Ok, I've re-checked the vero strips, solder connections, and have taken some voltage readings.  Some were a bit confusing to me.  See if this points to anything in particular.

Battery voltage = 9.16v
circuit voltage   = 9.16v

D1
A = .2mv
C = 9.1 v

D2
A = .2 mv
C = .9 mv

D3
A = .2 mv
C = .549v

Q1
E = 2.32v
B = 2.7v
C = 7.08v

Q2
E = 2.42v
B = 3.37v
C = 6.7v

Q3
E = .2mv
B = .2mv
C = 9.25v

Q4
E = .2mv
B = 3.6mv
C = 8.95v

Q5
E = 8.62v
B = 9.0v
C = 9.15v

IC
1 = moves quickly between about 20mv to 4 v, and then recycles continuously
2 = .6v
3 = 4.54v
4 = .3mv
5 = 393mv
6 = 2.94v
7 = 9.4v
8 = 198mv

Any clues from this information would be greatly appreciated!  Thanks!

[m-theory]

Hey, it works!!!

The tiny jumper that connects c7 to r13 had a lead that had somehow worked its way underneath the vero conductive strip, and was not connected to the circuit!  I had to build another jumper to correct the defect, but as soon as I did, the damn thing worked! 

Thank you to all who provided me the motivation to continue with this!  I absolutely would've dumped this and bought a PCB, had it not been for your support, and particularly, the guidance of an unnamed VIP, who emailed me with advice and guidance!  Thank you all!

jj

[calculating_infinity]

Awesome, glad to hear you got it working!  Now I need to debug my tremulus lune.