My first SHO

Cardboard Tube Samurai · July 16, 2011, 04:36:01 AM

PICSORBAN!!! Srsly, do everyone a favour and post some pics.

I have just spent the last two days with my head well immersed in this circuit, going over it with a fine toothed comb (followed a schematic with errors

). If you post up a pic, I can probably point out the problem straight away. Quit screwing around and just post a pic! It might seem fine to you, but there's nothing quite like a second set of eyes

deadastronaut · July 16, 2011, 05:05:51 AM

+1...

wesman26 · July 29, 2011, 03:56:06 PM

Sorry this took so long, I needed a camera which is something I don't own (I rarely find need for one) and so with one procured, here are my pictures.

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Mike Burgundy · July 30, 2011, 10:33:59 AM

Just a quick glance: it's not easy to see, since the pic is a bit blurry and there appear to be some globules of solder where there aren't parts, but the input wire looks like it could short against ground, the output jack's ground is suspect (can't see where it's going exactly) and I can't see a connection between C2 and the transistor. Can't see diode orientation unfortunately.

wesman26 · August 02, 2011, 02:17:22 PM

I know it looks pretty nasty; it's certainly not my best work. I know the input wire looks pretty suspect, and I've done my best to keep it from shorting and I'm positive it doesn't, if it shorted against ground I wouldn't get any sound out of the pedal at all I'm pretty sure. The ground for the output looks bad too, almost as though it's connecting to the non-grounded side of D2 but I assure you all that it is connected appropriately and there's no short. These two wires have looked so wrong to me for so long that I've checked and rechecked them. I'll double check C2 and take a picture of diode orientation for you all once I get back to my apartment and just to be safe I'll check the aforementioned shotty-looking connections as well.

Aside from possible failure of diode orientation can anyone see any obvious reasons why the voltage of the Gate is so low?

wesman26 · August 08, 2011, 01:37:41 AM

Here's a better picture of the diodes.
Diodes

Mike Burgundy · August 08, 2011, 05:31:55 AM

Okay, if you are absolutely certain there are no shorts and/or cold joints, eliminate. Don't be disappointed if it does turn out to be wiring or soldering though, you've been staring at this for so long it's very possible you're missing something right under your nose - I know I do that all the time. Just keep going and think logically.
That gate bias is made by the voltage devider between the two 10M's. Take everything out of the equation that doesn't have anything to do with that.
So, unsocket the tranny. The diodes are just protection, so lift one end of each of those (effectively taking them out-of-circuit) and measure, battery, between R3 and R2 (should be really close to 9V), and between R1 andR2 (should be half of previous measurement.)
If that doesn't yield those values, figure out why. Are the R's in correct, well soldered (measure everything, reflow, etc). What else is connected to that that could influence it? The C's are open circuit to DC - or are they? They should be, but.... etc. Eventually you'll have the circuit undressed to leave only the fault, so you can solve the problem, and build the circuit back up again step by step.

deadastronaut · August 08, 2011, 05:37:55 AM

Quote from: wesman26 on June 29, 2011, 02:34:29 PM
I used my own layout because I figured it wouldn't matter.

maybe my wiring diagram is wrong?

DO YOU HAVE A PIC OF 'YOUR' SCHEMATIC?/..layout diagram?...

Mike Burgundy · August 08, 2011, 07:34:42 AM

Yup, big help too, even if at first you think "but the layout is obvious from the pictures" . It's easier to compare a sketch of your layout design to the schematic, and easier to compare pics of the real thing to the sketch. More information is always better.

Mike Burgundy · August 08, 2011, 07:46:30 AM

I know you checked the values already, so it's probably the camera, but the "top" - (Left on the diode picture) 10M resistor does not look like 10M color code *on that pic*. That would NOT explain the ckts behaviour though so it's probably nothing.

wesman26 · September 16, 2011, 12:04:55 PM

So I doubt anyone cares anymore but I've found the cause of my strange voltage readings. As it turns out, my voltmeter has an input impedance of 1M, which is way too low for measuring voltage through a 10M voltage divider. Factoring that in, the measurement of 0.75V is actually about right, and therefore my build is fine, which makes sense considering I continuity checked everything three times to make sure there were no rogue solder bridges. Something I noticed and fixed before looking so closely at the divider was a faulty connection on the second (middle) terminal of the pot; I had assumed that while that might be part of the problem the incorrect voltage from the divider was probably a bigger one and so I shrugged it off. I'm putting everything back together now (I disconnected everything from the circuit except the divider just to test it) and hopefully I can post some positive results soon. Thank you all for helping so much, I'm sorry I was too lazy to make and post my schematic, and I'm sorry you all had to deal with the frustration of my incompetence.

Mike Burgundy · September 17, 2011, 12:00:14 PM

Doh. Shoulda thoughta that one ;P 1M across the bottom 10M should get it bang on 0.75V.
Let us know if it's okay now, happy soldering!

wesman26 · September 17, 2011, 01:38:31 PM

Yup, it was an awful(ly hilarious) realization, and once I powered out the math the 0.75V made perfect sense. It does work now! I replaced the 10M's with 1M's, but the general idea should make it fine regardless. Thank you all again for all your help and for putting up with my having "new" written on my forehead. Took forever, but I'm horribly excited to be moving on to other projects!

Mike Burgundy · September 17, 2011, 05:52:01 PM

Hey, *you* figured it out ;P

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My first SHO