No sound from a Refractor Professional Overdrive - Aion Electronics

[blackmad]

edit: schematic link - https://aionfx.com/app/files/docs/refractor_kit_documentation.pdf

Okay, so perhaps this was too ambitious for my first build, but I'm so close ... I think?

First problem a buddy identified was that I'd switched one of the op-amps and the voltage regulator ICs. I was getting absurdly incorrect voltage readings (as well as weird whining from the pedal in certain gain positions). After switching them, I now get almost entirely correct voltage readings on everything, but now no sound at all.

The only two pins that seem wrong right now are
ic3-6 = 2.5v
ic3-7=1.4v

ic3-4 I'm having a hard time getting a consistent reading on but I think that's just because it's so close to a cap that I keep shorting it when sticking in the probe? When I do get a reading it's right.
ic3-8 is being weird sometimes when I hit it the LED blinks off, but when it's right it's right. again I'm guessing I'm shorting something.

Other mistake: burned the insulation on one of the ribbon cables. Visual inspection says the wire core is fine, and multimeter says continuity is fine, so I *think* that's okay?

Did I fry the diodes? What should I try checking next?

[aion]

I'm still seeing the LT1054 in the upper left socket (IC1) when it should be in the bottom-center position (IC3). Are the photos from before the IC switch?

[blackmad]

Yep. Sorry about that. Photos are from before the switch.

[ElectricDruid]

How does the LT1054 cope with having 9V fed to pin 8 when pin 4 is grounded? And 4.5V on some other pins?

I've not stuck one in an op-amp socket as yet, so I don't know how well they survive the experience. I *can* tell you how well 78L05 regulators survive being reversed with some confidence!

I suppose a quick voltmeter check of the supply voltages would tell us whether the chip is alive and well. Could you test the voltages on the central op-amp, blackmad? Ground the black probe, and then read the pin 4 and pin 8 voltages with the red probe.

[duck_arse]

also welcome to the forum. but you'd be posting links, at least, to those build docs you have there in front of you, wouldn't you? just so we know what it is we are looking at.

[blackmad]

thanks for the welcome - apologies for forgetting the link - added it up top - https://aionfx.com/app/files/docs/refractor_kit_documentation.pdf

[blackmad]

How does the LT1054 cope with having 9V fed to pin 8 when pin 4 is grounded? And 4.5V on some other pins?

I've not stuck one in an op-amp socket as yet, so I don't know how well they survive the experience. I *can* tell you how well 78L05 regulators survive being reversed with some confidence!

I suppose a quick voltmeter check of the supply voltages would tell us whether the chip is alive and well. Could you test the voltages on the central op-amp, blackmad? Ground the black probe, and then read the pin 4 and pin 8 voltages with the red probe.

I ran through all the IC voltages after swapping the chips and everything on the op-amps (ic1& ic2 in the diagram https://aionfx.com/app/files/docs/refractor_kit_documentation.pdf) was within 0.5v range of the ones listed on page 24 of the kit docs

[ElectricDruid]

I ran through all the IC voltages after swapping the chips and everything on the op-amps (ic1& ic2 in the diagram https://aionfx.com/app/files/docs/refractor_kit_documentation.pdf) was within 0.5v range of the ones listed on page 24 of the kit docs

Ok! That sounds like you got away with it, and that means the LT1054 is tough little thing, so I learned something too!

0.5V is "a bit" in a situation like this, so it's not insignificant, but if nothing's way out, it's probably ok. And "page 24"?!? Jeez, this is serious task! That's not a build doc, it's a novel!

[bluebunny]

And "page 24"?!? Jeez, this is serious task! That's not a build doc, it's a novel!

(TBF, that would be about average for the astronaut fella...)

[blackmad]

So ... given I'm still not getting sound out of this, what should I try next?

I see that the ic3 pins I'm getting weird readings on aren't actually connected to anything, so maybe it doesn't matter that they're off from the manual's reference values?

what else have I likely fried?

[blackmad]

okay, ran a multimeter across my diodes


rectifier diodes - 0.56v across both
zenner diode - 0.57v

germanium diodes - um, these are giving LOST vibes, mulitmeter beeps, shows something around 1.1v and then rapidly runs down to 0v. should I assume from this that I fried the mythical sensitive klon germanium diodes?

[bluebunny]

They're not mythical!      But they (Ge) are more sensitive to heat.  Did you use a heatsink when soldering them?

[duck_arse]

okay, ran a multimeter across my diodes


rectifier diodes - 0.56v across both
zenner diode - 0.57v

germanium diodes - um, these are giving LOST vibes, mulitmeter beeps, shows something around 1.1v and then rapidly runs down to 0v. should I assume from this that I fried the mythical sensitive klon germanium diodes?

I have questions about your method. what is your method for testing the diodes, are you using the ohms range or the diode test range? either way, you test with the power off. if you are measuring on a voltage range, you obvs have power applied. I wouldn't worry about the rectifiers, they are plenty tuff enough to stare down a charge pump IC. the zener is there for over-volts in, should be able to stare down an external supply, because that is its job.

if you are reading the correct Vx voltages as listed on the circuit diagram, I wouldn't worry about any those three diodes, spend time looking elsewhere.

I dunno what "D.SW" is or does, but those two germs should read about 200mV on diode test, both ways.

[blackmad]

for testing the diodes - I disconnected the pedal from ac power, set my multimeter to diode test mode, placed the black lead on the side with the stripe, red on the other.

Since it looks like I'm getting reasonable voltage drop readings across the other diodes, it seems weird to me that the germanium ones don't give me a reasonable reading.

Any other places you'd suggest looking in the circuit? I get a signal coming out of the pedal when it's off and true bypass is enabled, so it seems like at least parts of the I/O are correctly wired.

[bluebunny]

You need to lift one end of one of those Ge diodes when you make the V_f measurements (but watch out for overheating them!).  They're in parallel with each other, so trying to get a measurement when they're still connected to each other will end in tears.

The other diodes will read fine, since they're not in parallel with any others.

[blackmad]

So I took the pedal over to a friend's place who likes to build pedals & eurorack modules. We hooked it up to an oscilloscope and fed a sine wave into it from his rack. We traced the signal the whole way through and could happily see the signal the whole way, then we hooked it up to headphones and heard the sound. Amazing.

At one point, he noticed that the gain knob was "reversed" but then said something like "that's from a crazy nonstandard eurorack that outputs weird voltages, let's put something in that's more like a guitar" so we used a different oscillator on a different rack and the gain knob worked "correctly"

I brought it home, plugged my guitar into one side and my amp into the other and ... nothing. No sound. being passed through in buffered bypass mode with the pedal bypassed or not. I tried three different power supplies and two different cables. I plugged my guitar directly into the amp and heard sound. I feel insane. What could be going wrong?

[duck_arse]

headphones. there's a clue. they would have a stereo jack plug. if you have miswired in some manner the output jack, a mono plug might be shorting the signal to ground. otherwise, what is different in your setup? get his phones at your place, your guitar, your power supply, and what happens?