Vibra-Tone : two tries and still failure... what the hell?

[bluesdevil]

Hi - I can't believe my bad luck with this project..... second try from scratch and still can't get it to work. I will post pin voltages here after one last trace bridge check and reflowing of possible cold joints, but just thought I would post here first with a question or 2. The weird thing is in both my attempts I get the buffered straight signal. but no effect..... I gotta be doing the same thing wrong each time. The question is can the jfets I'm using not be up to snuff for this circuit? I'm using the specified 2n5952 with voltages on the "improved Jfet matcher" around the 1.5 - 1.9 range and matched pairs where needed. Is that enough voltage to activate the lfo?
Here's the layout:
http://www.aronnelson.com/gallery/main.php/v/MarkMs-Gallery/album15/album76/Vibrato+LAYOUT.png.html
    Only change from the layout is I bypassed the PNP +9v switcher circuit by putting the +9v wire to the pad where the collector leg would go. Also I noted the reversed c9 polarity mistake mentioned in a recent thread.... still no luck.
    Reminds me of that Bad Stone build from a few years ago, this one's driving me absolutely nuts as well, haha!!

[Ry]

The problem with that layout is that it is a combination of RG's previous and current versions of the circuit.  It falls apart at the R14/Q4 part of the circuit all the way to the output.  I pulled everything after Q4 off the circuit board and wired it up on a bit of perf board.  Check the layout vs. the latest schematic at GEO and you'll see what I mean.  It sounds wonderful, just keep at it.

Ry

[bluesdevil]

Thanks Ry, that's a damned good tip!! I'll get on it right now and post back with my results later.

[bluesdevil]

Found my mistake and now it's working!!!! I was in the process of tracing the layout with R.G.'s schematic as a guide when I noticed the ground wire on the Depth control's lug 1 was missing. Wired it up, plugged 'er in and there it was!! I'm still tracing out the circuit to see what other differences can be found for the hell of it. I did run into different value resistors off the 3rd lugs of the Speed control (1k on schematic compared to 2.2k on layout)... not sure if that really matters or not.
   Volume is definitely still very low even with the jfet booster stage.... might try R.G.'s Darlington thing or just go with a LPB circuit or even that TL072 booster floating around for certain Flanger/Phaser builds. Also I wired up 2 separate 100k pots instead of a dual just temp I thought, but I actually like how it sounds with one of 'em full up and the other a little bit down. Not as choppy and a better texture to my ears. The only problem  with using 'em separately is that you can stall out the LFO if one goes to much lower than the other.
    A very nice sounding effect when adjusted to taste.... just need that volume boosted now.
I gotta thank R.G. and Markm for their efforts and for sharing this one. Also thanks to Ry for the reminder that it's always a good idea to check the schematic even when building from  a "verified" layout.

[tskullt]

Hi everyone,
  Is there a sound clip out there for this one?  I'm really interested in this one!
thanks,
m.

[markm]

The layout in this post is a modified version that I made last year in an attempt to remedy the volume drop some had
experienced with this circuit. When I built the original with some help from R.G., I had no volume issues at all although
I have heard quite a few that have had volume issues and many that have not. The schem on R.G.'s site I beleive is his
corrected version that addresses the volume drop as well hence the reason the schem doesn't match the layout.
This probably is of no help but, if I remember correctly this is the reason for the mis-match.

[bluesdevil]

Hey Markm - Good to see ya here again!! Your layout definitely works. Not showing that Depth pot lug 1 ground connection is what threw me, sad but true.  For the volume problem I'll probably just bypass your booster stage with one of my own on a separate board.
    That was a helluva layout to put together, it's appreciated for sure. I'll try to whip up a quick sound clip today and post a link in this thread.

[Ry]

I guess I took the brute force method of debugging my build...re-building parts of it on a perf board.  I wonder what I did wrong.

Good to see you around again, Markm.

[markm]

Thanks for the kind words fellas.
I believe John Lyons has a sound clip of this build.

[bluesdevil]

Okay, here's a sound sample I just whipped up:
http://www.aronnelson.com/gallery/main.php/v/bluesdevil/vibratonesample.mp3.html

Funny how I always choke a bit when I record, but not too bad, ha!
Noticed my folder being empty on the layout site... I wonder what happened? Hope this clip doesn't get deleted too.

[tskullt]

Hey Bluesdevil,
  Thanks for the sample, not too bad is right!!!!  Gotta get an parts order together, this one sounds like a keeper!
m.