Debugging help please!

[jkokura]

Alrighty, I read the debugging sticky, and though I don't have all the info right now, I'll be able to use a DMM tonight and get more details, but I thought I'd start by posting and then adding later.

I've got two projects on the table right now, and three more behind them that might not be working either, but I'll make a separate post about each pedal rather than have them all in one post. This post is for an Orange Screamer - I got the PCB from Tonepad (http://www.tonepad.com/project.asp?id=5) and parts from Smallbear. No Mods, just the stock

Now the problem. There's no sound when I turn the pedal on. I've checked both my cables, they aren't the problem. I get signal in bypass and it sound like there's no loss, so the bypass part of the circuit is good at least. As you can see below, I get a light in the LED when the circuit is active, but no sound. So my first diagnosis is either that my wiring is bad from the switch to board or from the switch to the jacks - but since it works in bypass I didn't think the latter as likely as the former. So used my DMM last night to check continuity from the switch to board and it seems fine. That leads me to my second diagnosis, and that means something's wrong on the board. Help me out if you can please!

Here are some pics:




I know it's likely someone's going to say - those pictures suck. I'll try and get better ones up tonight. In the meantime, if anyone has a suggestion, I'm very new to debugging, and while the debugging page is helpful, I'm also new to a DMM (though I think I've got checking continuity down).

Please help.

[jkokura]

1.What does it do, not do, and sound like?

In Bypass I have good clean signal. When active, no sound at all, but the LED comes on.

2.Name of the circuit =

Orange Squeezer

3.Source of the circuit (URL of schematic or project) =

http://www.tonepad.com/getFile.asp?id=88

4.Any modifications to the circuit? Y or N

No

5.Any parts substitutions? If yes, list them.

No

6.Positive ground to negative ground conversion? Y or N

I think it's Negative... Not sure on that one. Someone looking at the Tonepad site wanna tell me?

7.Turn your meter on, set it to the 10V or 20V scale. Remove the battery from the battery clip. Probe the battery terminals with the meter leads before putting it in the clip. What is the out of circuit battery voltage? =>

8.61

Now insert the battery into the clip. If your effect is wired so that a plug must be in the input or output jack to turn the battery power on, insert one end of a cord into that jack. Connect the negative/black meter lead to signal ground by clipping the negative/black lead to the outer sleeve of the input or output jack, whichever does not have a plug in it. With the negative lead on signal ground, measure the following:
Voltage at the circuit board end of the red battery lead =

8.59

Voltage at the circuit board end of the black battery lead =

0

Q1
1 = 1.59
2 = 1.7
3 = 0

Q2
1 = 8.56
2 = 2.45
3 = 1.7

IC1 (or U1)
P1 8.04
P2 8.04
P3 0
P4 0
P5 4.59
P6 4.68
P7 4.68
P8 0

D1
A (anode, the non-band end) = 0
K (cathode, the banded end) = 0


I think I measured everything right. I wish I had an alligator clip end on my black DMM pin.

[spaceace76]

double check that your IC is inserted correctly, or that at least you're measuring the right pins. pin 5, for example, should be pretty close to your battery voltage. someone correct me if i'm wrong on that. also, make sure you're FET's and the immediately surrounding components are soldered correctly, 0 volts on a transistor means there's an issue in that area. A picture of the solder side of the board would also help.

have you built an audio probe? those are invaluable debugging tools

[jkokura]

I measured the IC with the dot at the upper left corner, beside Pin 1:


1   8
2   7
3   6
4   5

I will examine the 0 at the transistor, and the 0's and low voltage on the IC.

I have not built an audio probe, I actually have launched into these projects full bore, and am only now catching up to the fact that I have to learn to debug. I have a DMM cause they were on sale months back, and only got it going this past weekend as I learned I needed it. Is it safe to assume that an audio probe is redundant with a DMM, or am I off base?

By the way, my name is Jacob. Long time lurker (6-9 months), new poster.

[jkokura]

I got some better pictures and some soldering done. I looked closely, unsoldered and then resoldered the joints you mentioned. They are now much better done than they were, but it produced little to no positive change in the voltage readings. They all resemble the list I made above. I also examined and resoldered other joints, and it also made little to no difference.

Here are some macro closeups done with a 10MP PAS rather than my pathetic iPhone 3G cam.
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Any help is greatly appreciated.

[spaceace76]

those last two img tags don't seem to be working, but i saw a couple new photos at your imageshack page. nothings really jumping out at me in terms of soldering.

by no means does a DMM make an audio probe redundant. you can immediately isolate a problem by following the signal path with an audio probe. it's probably the quickest way to debug this.

the voltages at pins 5 and 8 stand out to me. from how you measured it, pin 8 is right off the 9v power rail, but you're somehow getting 0 volts there, and then over on pin 5 you've got 4.59. If the IC isn't getting power, it would definitely explain why you get no sound. make sure you've got continuity from the IC socket to the red lead on the board, and all the way back to the positive terminal on the battery clip.

also double check that your FET's have the proper pinout. different manufacturers sometimes have different pinouts for the same devices.

hope that helps

[GP]

Looking at your new imageshack pictures, i can't see any obvious shorts etc.

Pin 4 (not 5) should be connected to ground - 0 volts - and pin 8 should be connected to 9V. It's almost like you have the battery leads connected the wrong way round but it doesn't look this way from the pictures. Are you sure you have your DMM connected the right way round? The black lead should be in the black connector on your DMM (marked COM or probably coloured black anyway). Vice versa with the red lead.

[anchovie]

Looking at your new imageshack pictures, i can't see any obvious shorts etc.

Pin 4 (not 5) should be connected to ground - 0 volts - and pin 8 should be connected to 9V. It's almost like you have the battery leads connected the wrong way round but it doesn't look this way from the pictures. Are you sure you have your DMM connected the right way round? The black lead should be in the black connector on your DMM (marked COM or probably coloured black anyway). Vice versa with the red lead.

He gave measurements of 0V for both pins 4 & 8, it's not a PSU polarity issue.

The 0V reading on Q1 is perfectly acceptable given the way it's set up (whichever way you go from that top pin in the schematic you end up hitting a capacitor, so all DC to that point has been blocked).

Take the chip out of the socket and measure the voltages of the socket itself.

[jkokura]

I now have voltage on pin 8 that I didn't have before after removing and reseating the IC. I haven't got an amp or guitar handy to check it out here, so I'll put this back in it's box and check it at work tomorrow. Now I'm going to post on another pedal issue.

[Pakaloabob]

This is probably no help at all, and I apologize for sticking my nose in, but you can ignore me if you want.
I also had issues with my Squeezer. Etched board from Tonepad transfer. Mine worked in bypass but not with effect engaged. I am not experienced at all in debugging and got frustrated trying to probe the circuit with a multimeter. Using the audio probe I got sound from the input jack connection, but not on the board input. Made me think there was a short on the board. It was not a perfectly clean etch and solder job so I made a new board and resoldered. Now I get sound with effect engaged, but there doesn't seem to be an change from bypassed sound. I am wondering if I burnt out my transistors?
In the meantime I moved on to another project which worked fine. Helped with my confidence and satisfaction. I will be revisiting the Orange Squeezer until I get it working right.
I am following this thread to see what you wind up doing to fix the pedal. Hope it works out for you.

[jkokura]

Hey, it's working now, so the reseating of the IC and redo some soldering worked just fine! One pedal working, 4 more to go!

[spaceace76]

awesome! sometimes a little tinkering is all it takes. enjoy the pedal!