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Discussion Starter #1
Not sure if this is the right forum, but I've taken on my first pedal build and am now (inevitably) debugging it as it doesn't work.

It's an orange squeezer compressor clone that i bought years ago. Not sure that matters, but there you have it.

I could get highly detailed, but suffice it to stay, voltage seems to be at all the right places, but on the JFET transistors the voltages seem to be substantially different (lower) than the reference table the kit has in its instructions.

Not sure whether this tells me anything or not. These are voltages on the bench, without any cables plugged into the input or output jacks.

Any thoughts or tips? Is this a deadend lead or might it be telling me something?

For what it's worth, here is the link to the kit and schematics, etc.

Dan Armstrong™ Orange Squeezer™ | General Guitar Gadgets

Thanks!

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Discussion Starter #3
I'll post one momentarily. I am really embarrassed by my soldering skills though...

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Discussion Starter #5
If it makes matters any clearer, I can trace voltage all the way to the positive side of C6, but nothing after that (which may make sense...i understand DC voltage doesn't get through a capacitor?).

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Does tweaking the bias trimmer get your Jfet voltages closer?
 

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Discussion Starter #7
Good question...let me check. I tweaked it with the pedal plugged into an amp, but didn't go back and check the reference voltages.

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Discussion Starter #8
It does, yes. Still not quite right, but could be the accuracy of my meter...

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Yeah, I can dial in any of the gate, drain or source voltages to be right, but the others are all off a volt or so. But I suspect you're right, that's a red herring.

Anyone know how i can tell if the circuit is okay downstream of C6 - as I mentioned, i can trace voltages to the positive side of that validity, but after that nothing although I'm not sure that's a problem.

I guess next step is to try an audio probe or to resolder some of the more cringe inducing solders i have...

Thanks!

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Yeah, I can dial in any of the gate, drain or source voltages to be right, but the others are all off a volt or so. But I suspect you're right, that's a red herring.

Anyone know how i can tell if the circuit is okay downstream of C6 - as I mentioned, i can trace voltages to the positive side of that validity, but after that nothing although I'm not sure that's a problem.

I guess next step is to try an audio probe or to resolder some of the more cringe inducing solders i have...

Thanks!

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Yeah, it could be as simple as a tiny whisker of solder touching the pad next door throwing everything off. I never saw the board bottom pic until now - I'd *just touch* every one of your solder joints with a really hot iron (and hold the component in place on the other side), to eliminate any cold solder joints - make sure the iron touches both the component and the board. Hot hot hot, in and out in under a second just let the solder reflow. And I'd trim down the length of most of the component legs.

If you have an exacto type hobby knife, you can run it in between close together solders to make sure there aren't any unseen connections happening.
 

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1) If I'm going to troubleshoot a pedal, I always try to clean the copper side of the board first. I'll use an old toothbrush, and if there is a lot of flux I'll supplement with some methyl hydrate to dissolve the flux. Too many shiny spots/bits on a board makes it harder to spot solder bridges and broken traces that can yield malfunction.

2) I like to joke that, despite having only 3 pins, there seem to be around 837 different pinouts for FETs, depending on part number and manufacturer, defying what should be mathematically true. If possible, confirm the FET pinout with the datasheet for that manufacturer.

3) Stated test voltages are ballpark figures. They're certainly not wildly off, or shots in the dark. But one can have a perfectly-functioning circuit even though the meter probes are telling you something a little different than the drawing or service manual. Remember that the stated test voltages are not independent of the specific components in use. All the components have tolerances that they can be at the higher OR lower end of, resulting in different measured voltages.

4) A lot of those solder joints look like they might be "cold". You might want to reflow a lot of them.

5) Compressors are generally one of those effects that lead people trying them out in the store to remark "Is this thing on?". In the case of the Orange Squeezer, which has a reputation as one of the more "transparent" compressors - largely because of its simple audio path and very quick gain recovery time (although the gain in the OS never really changes; rather the attenuation ahead of the gain stage changes), this is even more true.

6) A useful strategy is to plug a signal source into the circuit, like a guitar, and measure the AC voltage at a succession of informative points. So, is the signal actually reaching the gain stage? Test for this by measuring the AC voltage (likely in the 10-80mv range) at the input pin of the op-amp. My drawing says this should be pin 5. Is the op-amp actually applying gain to the signal? Check for this on pin 7, and at the negative side of the 4.7uf output cap. If those check out, is the output signal actually reaching the output? Check for that on the wiper of the volume pot. If the audio path seems AOK, now check the sidechain. Is the crude rectifier doing its job? Look for a reasonable DC voltage on the stripe side of the diode. It should be a bit less than half the AC output voltage of the op-amp. And so on.

7) The degree of "squish" is a function not only of the setting of the trimmer but the gain of the op-amp. Armstrong's circuits were always aimed at bare minimum requirements to do what they did, only requiring/providing an on-off switch on the enclosure. One can get varying degrees of squish by adjusting the gain of the op-amp. That can be by changing the value of the feedback resistor (R9), the ground-leg resistor (R10), or both. Making R9 bigger/higher, or R10 lower, will increase gain, and the "push" that makes the FETs drop their resistance.

http://www.generalguitargadgets.com/pdf/ggg_osq_sc.pdf
 

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Discussion Starter #13
1) If I'm going to troubleshoot a pedal, I always try to clean the copper side of the board first. I'll use an old toothbrush, and if there is a lot of flux I'll supplement with some methyl hydrate to dissolve the flux. Too many shiny spots/bits on a board makes it harder to spot solder bridges and broken traces that can yield malfunction.

2) I like to joke that, despite having only 3 pins, there seem to be around 837 different pinouts for FETs, depending on part number and manufacturer, defying what should be mathematically true. If possible, confirm the FET pinout with the datasheet for that manufacturer.

3) Stated test voltages are ballpark figures. They're certainly not wildly off, or shots in the dark. But one can have a perfectly-functioning circuit even though the meter probes are telling you something a little different than the drawing or service manual. Remember that the stated test voltages are not independent of the specific components in use. All the components have tolerances that they can be at the higher OR lower end of, resulting in different measured voltages.

4) A lot of those solder joints look like they might be "cold". You might want to reflow a lot of them.

5) Compressors are generally one of those effects that lead people trying them out in the store to remark "Is this thing on?". In the case of the Orange Squeezer, which has a reputation as one of the more "transparent" compressors - largely because of its simple audio path and very quick gain recovery time (although the gain in the OS never really changes; rather the attenuation ahead of the gain stage changes), this is even more true.

6) A useful strategy is to plug a signal source into the circuit, like a guitar, and measure the AC voltage at a succession of informative points. So, is the signal actually reaching the gain stage? Test for this by measuring the AC voltage (likely in the 10-80mv range) at the input pin of the op-amp. My drawing says this should be pin 5. Is the op-amp actually applying gain to the signal? Check for this on pin 7, and at the negative side of the 4.7uf output cap. If those check out, is the output signal actually reaching the output? Check for that on the wiper of the volume pot. If the audio path seems AOK, now check the sidechain. Is the crude rectifier doing its job? Look for a reasonable DC voltage on the stripe side of the diode. It should be a bit less than half the AC output voltage of the op-amp. And so on.

7) The degree of "squish" is a function not only of the setting of the trimmer but the gain of the op-amp. Armstrong's circuits were always aimed at bare minimum requirements to do what they did, only requiring/providing an on-off switch on the enclosure. One can get varying degrees of squish by adjusting the gain of the op-amp. That can be by changing the value of the feedback resistor (R9), the ground-leg resistor (R10), or both. Making R9 bigger/higher, or R10 lower, will increase gain, and the "push" that makes the FETs drop their resistance.

http://www.generalguitargadgets.com/pdf/ggg_osq_sc.pdf
Thankyou!!!

I probably won't get back to it for a while, but will follow this list and report back

Appreciate the help - I know that took a while to write out.

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