SOLVED Deflector FV-1 reverb noise

[toddrace]

My Deflector reverb build doesn't work the way I expect it to. Any Density knob position left of 12 o'clock produces a whine with a sort of bitcrushed static underneath it. (I have a nice movie of the noise, but it doesn't look I can upload it. There's a high-pitched whistle, which may be common as the knob spins, then underneath that there's a static that downs everything else out. Twist the knob back up and the static and whistle fades back out.)

Everything else seem just fine. If I stay above 12 o'clock on the density knob the pedal sounds sounds great. But is that how it's suppose to be?

I'm a novice pedal builder with about 10 builds under my belt. This is my fourth PedalPCB build overall (the Low Tide mini may never work without a schematic for troubleshooting, if anyone cares), and my second FV-1 build (Unison Double Tracker works great!).

It seems like this would be related to the the section on the schematic related to the FV-1 clock and the Density control. So I started there, beginning with the capacitor. Troubleshooting so far:

• replaced replaced C14 (it tested fine)
• replaced R14, R15, R16 for good measure
• Swapped IC4 - CD4049UBE
• replaced Density B25k because why not (it tested fine, anyway)

None of that really did anything. So that leaves maybe a grounding issue but where and how to find it?

Any ideas from someone more experience than me greatly appreciated. Thanks!

[UPDATE] More, better lit photos if that helps.

 

[toddrace]

More updates:

• I re-flowed every joint.
• Replaced damaged caps.
• I cleaned the board really well, removing any fibers I could see with microscope, scrubbing off flux residue.
• Measured voltages, because it seems like something people do. Wall wart power supply measures 9.2v.

IC1 — TL072

1 — 4.42	5 — 4.25
2 — 4.42	6 — 4.42
3 — 2.09	7 — 4.43
4 — 0	8 — 8.88

IC2 — SPIN FV-1

1 — 1.51	8 — 3.31	15 — 3.3	22 — 0
2 — 1.51	9 — 1.42	16 — 0	23 — 3.3
3 — 1.6	10 — 0.31	17 — 0	24 — 0
4 — 0	11 — 0	18 — 0	25 — 0
5 — 3.31	12 — 0	19 — 0	26 — 3.3
6 — 0	13 — 3.24	20 — 0	27 — 1.7
7 — 0	14 — 3.3	21 — 0	28 — 1.71

IC3 — 24LC32A

1 — 0	5 — 3.29
2 — 0	6 — 3.29
3 — 0	7 — 0
4 — 0	8 — 3.31

IC4 — CD4049UB

1 — 3.31	9 — 0
2 — 1.59	10 — 3.31
3 — 1.5	11 — 0
4 — 1.49	12 — 3.31
5 — 1.49	13 — 0
6 — 1.57	14 — 0
7 — 3.31	15 — 3.3
8 — 0	16 — 0

IC5 — L78L33

1 — 8.88

2 — 0

3 — 3.31

Does this help anyone tell if power is distributed correctly? Would increasing a resistor value around the Density control effectively raise the bottom end of the pot above where the static/whine are occurring?

Pretty close to giving up on this thing and tossing it in the trash, but it's so close to working.

And any all insights appreciated.

Thanks!

 

[Laundryroom David]

I don’t really know, and there are others who probably will, but based on the schematic I am surprised to see pin 7 of the FV-1 giving you 9.22v. Schematic indicates that pin goes to ground. Again, I don’t want to send you on a wild goose chase, but that popped out at me.

 

[toddrace]

I don’t really know, and there are others who probably will, but based on the schematic I am surprised to see pin 7 of the FV-1 giving you 9.22v. Schematic indicates that pin goes to ground. Again, I don’t want to send you on a wild goose chase, but that popped out at me.

Ugh. We'll generously call that a "transcription error." It is in fact zeroes.

Thanks for catching that...

 

[Laundryroom David]

Dang. Sorry!

 

[Funnel]

If I'm reading the schematic right. Fv-1 pin 6 should be similar to pin 8 about 3.3v.

 

[Funnel]

also pin 3 of the tl072 is around 4v on my build

 

[toddrace]

If I'm reading the schematic right. Fv-1 pin 6 should be similar to pin 8 about 3.3v.

Thanks. I guess if I look at the schematic more closely, it should have 3.3v coming in at pin 6. That could be a problem.

I'll swap out IC1 as well tomorrow and report back.

I appreciate your eyes. The longer I've been looking at it, the more I'm hammering on the same areas and no longer thinking clearly about it.

 

[Funnel]

I have a troubleshooting shelf. I know how it goes. I have wanted to throw many a pedal against the wall. Specifically, one vero broadcast that I attempted years ago. I got one of two working after 4 attempts.

 

[Laundryroom David]

I have a troubleshooting shelf. I know how it goes. I have wanted to throw many a pedal against the wall. Specifically, one vero broadcast that I attempted years ago. I got one of two working after 4 attempts.

Same. I call mine The Shelf of Shame. Mods gone wrong. “Learning Experiences”.

 

[toddrace]

Old business:

• FV-1 pin 6 measures 3.3v. I swear to god it was 0 before because I remember thinking "Hm. No analog power. Maybe it just needs the digital power supply." Or I am getting really sloppy.
• Pin 3 on the TL072 is confirmed at 2.09v, as are the reciprocal components around it. Odd that other builds sit around 4v. I have not idea of this means anything.

New evidence:

• So, I accidentally got the pedal to work as expected. While twiddling knobs, I shorted my thumb across the three posts of the Mix/Dilute pot. When I did that, I can turn the Density knob to any position without static or whine.
• That experiment is repeatable. If I mess around with Density and I DON'T short the Dilute pot, the noise comes back when I go below 12 o'clock.
• So, I guess the investigation moves to the components and grounding relate to the Dilute control...?

Thanks for the help so far. I was pretty close to chucking this thing in the garbage, but I feel like I at least have a direction now. (And I didn't want to scrap a precious FV-1 chip.)

 

[Robert]

I haven't heard your clip, but one thing to keep in mind is that there will be some whining / digital artifacts when the Density knob is at it's lowest settings.

Density controls the FV-1 clock frequency and things get a little strange when it's running at the lower extreme, but I think noon is probably a bit too soon for that to be happening.


Your DMM is most likely loading down the voltage reading on pin 3 of the TL072. The pull-up resistor is 1M so if your meter doesn't have a high internal resistance it will affect that reading. If the voltage on pin 1 is closer to 4.5V (and we're assuming the TL072 is good) you can move on past that.

 

[toddrace]

Thanks for your reply, Robert.

Pin 1 of the TL072 is 4.42v. I'm using a Klein MM300, which does have some limitations, though the ceiling is supposed to be 2M.

Since I can trick the pedal into sounding right for a while by touching all three legs of the Mix knob as I change the Density knob, I'm going to assumed everything is more or less okay with the basic functioning of the FV-1 and investigate the components between FV-1 pin 28 and Mix pot. It still seems logical to me that there must be a grounding issue somewhere. (Although "logical to me" isn't based on any working experience or actual understanding of what may be going on.)

Thanks again!

 

[toddrace]

I’m marking this one solved. Ignominiously solved, but happily solved.

I bought another PCB and carefully populated it while cross-referencing the original build. I discovered an incorrect cap value at C9 (another 10u). I replaced it with a 4u7 and plugged it in for a new test run.

Nothing changed. The whine is still there…

But then I realized the real solution was knowin’ when to fold ‘em. I finished up the new build and it works perfectly. Sounds great. I’m happy.

I actually improved my skills quite a bit and acquired some new tool to help with checking every component and troubleshooting. Live and learn. Keep building.

Thanks for the help!

 

[Gordo]

I've had one or two boards that was the same thing. Troubleshoot till you're blue in the face and nothing and the only way around it was to start fresh. You'll probably find a buggered up trace or something that was staring you right in the face if you decide to revisit it. And for the prices of FV-1's lately it's worth a revisit. For what it's worth the Deflector has been on my live board since Robert introduced it, I LOVE this pedal.