Vox wah help! pcb?

[jpiddy118]

Hey guys, i'm in wah pedal hell... found an old Vox shell at a garage sale, rigged it up with all the hardware, Icar 100k pot, Eye-Rock inductor, and tried a Vero board layout found online. Never did a Vero before, hated the entire process (esp the soldering), and to top it off, no sound. Bypass works. BC109s are showing 6v collector voltage with 9v battery attached. Tried testing continuity with my DMM but it doesnt seem to like capacitors (am I doing it wrong?)

If anyone has a Vox or compatible pcb (empty), i'll gladly buy or trade for it.

[jpiddy118]

update: using an audio probe, i discovered a few things:

1. signal is getting from input to Q1 base. Barely any signal is leaving Q1 Collector though (voltage on both Q1 C & Q2 C is 4.4ish).
2. the same level of signal leaving Q1 C is getting to Q2 B, and guess what? About half is leaving Q2 C.
3. That same level is leaving the pedal output, and the biggest surprise of all is, it stays the same whether battery connected or not (battery is reading 9v while connected to circuit). 
4. tried reversing BC109s... no difference. Tried a diff Si tran, no difference. DMM says they're both getting juice.

i'm about ready to throw this thing out the window.

Anyone? Bueller? BUELLER?!?

ps- i'm using Ulysses' v846 vero layout, and have triple-checked everything including resistor values.

[Govmnt_Lacky]

A link to the project layout/schematic would help.

Also, some pics of the board on both sides 

[jpiddy118]

I guess that might help, silly me...







and the layout: http://www.aronnelson.com/gallery/main.php?g2_view=keyalbum.KeywordAlbum&g2_keyword=Vox+V846+Wah+1590B+Vero+Layout+Ulysses&g2_itemId=6509&g2_imageViewsIndex=1

FYI, you may notice I substituted a couple resistor values for something else in the neighborhood that i already had... nothing huge.

Thanks!!!

[Govmnt_Lacky]

Two things that stick out right away...

1) Take a good look at the Input jack. From the pics you posted it looks like the both the Ring and Tip are touching.

2) It looks like there may be some solder runs on the stripboard. Check your connections.

EDIT: Also looks like you have some leads poking through the stripboard that were not soldered very well. Specifically near the top-center of your picture.

[jpiddy118]

Thanks Govmnt Lacky...

1. haven't connected the ring to anything, should it be wired to battery -9v? My ground scheme has continuity throughout the circuit, i followed wiring per Ulysses' vero layout.

2. checked continuity on every strip, including jumpers & breaks, and ran an Xacto between every strip. Cleaned up a few spots before the last time i tested.

3. i'll double-check those leads when i get home tonight. I assure you nothing was loose, but i had a b*tch of a time soldering this vero board. Consider myself pretty solid with pcb soldering, but this was a real pain.


EDIT: looking at the schematic, and DUH, of course i shouldve connected the battery -9v to the input ring. A little annoyed with myself for missing that. Can't correct this til tonight. BUT, i'm still confused why the transistors have 4.5v at Collector but aren't doing their job?

[Govmnt_Lacky]

1) Definitely connect the V- from the battery to the Input jack Ring. This will ensure that the circuit only gets power when you have a cord plugged into it. (Why would you need it any other time + it saves battery life  )

2) Check and make sure that your inductor is using the correct outputs. Some inductors have from 4 to 8 posts on them BUT only 2 are used. Make sure you have the correct 2 in the circuit. You can usually do this by just measuring resistance between the 2 points that you used. It should be low enough (between 10 and 50 ohms) to read IN CIRCUIT. No resistance reading/open = WRONG 2 points  

3) Put a hot soldering iron on any questionable joints. Let the solder re-flow to eliminate any cold solder joints.

Good Luck  

EDIT: According to the layout, the Inductor pins SHOULD be in J12 and F16.

[jpiddy118]

Thanks again!

I did check the inductor, and i believe it measured about 30 ohms. It came with only two pins extended, and those happened to line up in this layout perfectly.

[jpiddy118]

Need to resurrect this one... got a Vox pcb from Pigeon fx, thinking my problems were due to my first vero attempt. I loaded up the board, wired it into the enclosure, and nada... same results as the vero. double-checked soldering, transistors, etc. I'm stumped.

[geertjacobs]

Please use the debugging thread as a starting point.

[jpiddy118]

Links to schematic & layout:

http://pigeonfx.com/layouts/layoutv846.html

http://www.aronnelson.com/gallery/main.php/v/ulysses/ulysses_layouts/ulysses_vox_v846_wah/vox_v846_vero_ulysses_1_1.gif.html?g2_imageViewsIndex=1

pics of my work:





Q1 C 0.26, B 0.88, E 0.18
Q2 C 9.38, B 0.56, E 0.06

Inductor giving me 31ohms in circuit

[jpiddy118]

wow... after posting all that info, and checking Q voltages, i noticed the problem... Pigeon layout Q1 B & C aren't in typical order. Since I was using 2n2369a's, i was paying more attention to the E position. Well, that's why they call it debugging. Thanks for the help again, i'm learning!!!


Also, maybe it's a noob thing to gripe about, but I found the Pigeon layout kind of annoying compared to the GGG boards i've been using. Had to drill a few extra holes to make things fit in a more conventional manner. Q1 orientation is the 3rd or 4th thing I foudn to be kinda out of whack. Oh well, it works!

[geertjacobs]

I was wondering whether your 10k resistor was really 10k?

[jpiddy118]

it's actually an 8.2k, all i had on hand. Also used a 68k in place of 33k for the "vocal mod" i read about somewhere around here.

[jpiddy118]

Didn't notice this earlier... with wah engaged, it only passes signal with input jack 1/2 way in (must have been this way inadvertently when i last checked). Bypass does not work this way though... bypass only passes signal with jack in full (correctly). the wah circuit seems to be getting signal from the ring tap, but the only thing connected to the ring is the battery -9v. I took the wah circuit input lead, connected it directly to input jack tip, and still nada. if i touch ring, it passes signal. Never had this problem with any other builds. This wah is a box of headaches!

[Govmnt_Lacky]

Input jack wired wrong??

Get out your DMM and check it. 

Also... I could be wrong but, your sweep pot looks odd! Are you sure that the outside lug is supposed to go to the DPDT switch? I would think the MIDDLE lug should go back to the switch.

[jpiddy118]

according the the original schem and various layouts, wiper lug 2 of sweep pot goes back to circuit at base of Q2, and 3rd lug goes to output. I followed the Pigeon FX layout, others are similar.

regarding input jack, i can't see where i screwed this up... tip to DPDT to circuit input, ring to battery -9v, sleeve to ground, like every other pedal i've successfully built. Bypass works fine. How the heck is signal getting from the ring to the circuit?!?

FYI, i used this layout for my DPDT wiring: http://www.generalguitargadgets.com/diagrams/wah_847_lo_tb.gif

[Talon5051]

I see three solder joints on the PCB that are not soldered very well.  There is one in the upper left hand corner, one in the upper right hand corner and one center left.  These 3 connections could be causing most of your problems.  Resolder them and then go over all of the connections with a magnifying glass.

[jpiddy118]

Thanks for pointing those out Talon, i re-soldered them and a few others i noticed, re-seated my input lead, and now it works! Also, part of the pcb was touching the case and causing a 50% drop in volume, put a little foam in between and now it's solid.

Thanks to all who helped this noob with his wah headaches!