Aion Electronics Stratus OD - no gain, no volume boost

[EBK]

I measured resistance between the drive lugs as well:
Anti Clockwise - 0 ohms between 2 and 3 as well as 2 and 1.     I think this is the problem?
clockwise - 0 ohms between 2 and 3, 1 between 2 and 1.

Almost certainly something shorting out.  That's why I asked if the back of the pots were touching something on the board.  I'll go out on a limb and suggest the pot itself is probably fine.  I'd generally expect infinite resistance to be a more common failure mode for those (I reserve the right to be utterly wrong, of course ).
By the way, if you want something that gives you a little more leeway than electrical tape, try some double stick foam tape (you can leave the backing on one side if you want single stick).  Gives you some thickness that makes it less likely that a solder joint will poke through. 

....
Yes, R2 is omitted in this variant.

That remains one of my favorite PCB designs of all time (even though I have never owned one...), but it does give you a lot to keep track of.  As far as I can tell, you didn't miss anything, unless you jumbled some part values. 

[suryabeep]

Thank you for the advice, I'll check for shorts on the drive pot.

[EBK]

If you measure the resistance between pins 6 and 7 of the op amp, do you get 51k?

[robthequiet]

Check the pcb in case the solder might have spilled over on pins 1 & 3 on the drive pot.

[suryabeep]

There's no solder spillover. For some reason the meter shows 1 for resistance between pins 6 and 7 as well as 7 and 8. It shows 4k for resistance between 5 and 6. I may be doing this wrong though so...


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[robthequiet]

Yes, measuring resistance in circuit is tricky because you're measuring the resistance of what is outside of the chip in parallel with what is inside. If that makes any sense.

My concern was to make sure the gain pot is working. If it is shorted from pin 3 to pin 1 it's obviously working as a wire jumper. But Eric's suggestion makes sense, in that we're trying to isolate, or what I call divide and conquer.

Could be a bad pot, although as Eric says a bad one is more likely open than short. If it is PCB mounted that suggests a shorted trace or solder bridge. In a short situation, the only way to get it out of the circuit is to remove or cut it. Maybe we could replace R6 with a 150K resistor to see if we get a bit of gain?

[EBK]

Yes, measuring resistance in circuit is tricky because you're measuring the resistance of what is outside of the chip in parallel with what is inside. If that makes any sense.

True, but in this case, pin 6 is the gate of a JFET, spec'd at 10^12 ohms (1 teraohm) impedance. 

If it isn't a solder bridge, it could be a bad chip, bad socket, C3 could be shorting, or something in the clipping network is shorting.

[duck_arse]

suryabeep - can you pull the whole thing outta the case, and show us the solder side of your board, please?

[suryabeep]

This is the best view I can get, it's hard to take a clear shot with all the stuff in the way

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[duck_arse]

is there any prick-marks in the tape on the back of the pots you can see? and has the working changed any since it is out of the case?

[ElectricDruid]

is there any prick-marks in the tape on the back of the pots you can see? and has the working changed any since it is out of the case?

+1, both very relevant questions.

Tom

[suryabeep]

There are no visible prick marks on the tape, and it is still the same even after taking it out of the box and moving the pots away from the board.
Should I replace the drive pot? The IC?


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[EBK]

There are no visible prick marks on the tape, and it is still the same even after taking it out of the box and moving the pots away from the board.
Should I replace the drive pot? The IC?


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Pull out the IC and measure between pins 6 and 7 again, both the empty socket's pins and the isolated chip's pins.

[suryabeep]

There are no visible prick marks on the tape, and it is still the same even after taking it out of the box and moving the pots away from the board.
Should I replace the drive pot? The IC?


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Pull out the IC and measure between pins 6 and 7 again, both the empty socket's pins and the isolated chip's pins.

The resistance right?


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[EBK]

Yes, resistance.

[redmojosteve]

Hi. This may not be too helpful as although I have built quite a few stomp boxes and other audio gear, I'm actually a mechanical engineer rather than electrical, but I do know my way around a multimeter and a 'scope! There are a couple of things I would suggest. I always use separate ground wires as I don't like or rely on cleaning paint or corrosion, which seems better for longevity. It also means you can test the pedal out of the enclosure which means it's easier to poke around with the multimeter prods on both sides of the board. I am sorry to be stating the obvious, but the first things I also check for if it doesn't work would be shorts ( which I think you've checked, solder bridges etc) and also dry joints. It's not too easy to tell from the photos but the solder on some of the joints does not seem to have flowed too well and it might be worth putting a hot soldering iron on the joints just to be sure all of the connections are sound. Good luck
Steve

[suryabeep]

Pull out the IC and measure between pins 6 and 7 again, both the empty socket's pins and the isolated chip's pins.

The empty socket's pin 6 & 7 resistance is 873K, The isolated IC's pins are not connected (DMM reads 1. on the left side of screen?).

Hi. This may not be too helpful as although I have built quite a few stomp boxes and other audio gear, I'm actually a mechanical engineer rather than electrical, but I do know my way around a multimeter and a 'scope! There are a couple of things I would suggest. I always use separate ground wires as I don't like or rely on cleaning paint or corrosion, which seems better for longevity. It also means you can test the pedal out of the enclosure which means it's easier to poke around with the multimeter prods on both sides of the board. I am sorry to be stating the obvious, but the first things I also check for if it doesn't work would be shorts ( which I think you've checked, solder bridges etc) and also dry joints. It's not too easy to tell from the photos but the solder on some of the joints does not seem to have flowed too well and it might be worth putting a hot soldering iron on the joints just to be sure all of the connections are sound. Good luck
Steve

I've installed separate ground wires on your suggestion and reflowed all joints. Still the same problem

[EBK]

Hmm...  Are we misinterpreting your meter?
Does it show a one for overflow? (i.e., outside of range or open circuit).  I was thinking you were telling us it was measuring one ohm.

We'd expect the meter to show open circuit for the isolated chip, so that would be good.

Instead of a short circuit on your board, you may have a break instead.

[suryabeep]

When there is no connection or infinite resistance, my meter shows a 1 on the left of the screen.
Pardon the noobery, but is overflow the same as no connection?

[ElectricDruid]

That's useful to know, but there's still a short across the drive pot somewhere. That was reading 0 between terminals that should have been hundreds of Kohms.

T.