Rangefnder - new whine after 8 months

[mkstewartesq]

OK, this one has me stumped. One of my very earliest builds (about eight months ago) was the Rangefinder. It has worked fine for the past eight months, other than a minor issue where I could not quite bias the transistor to 7 V. When I flipped it on a few nights ago, I noticed a high-pitched whine (basically a tea kettle whistle) that had never been there before. It appears to be coming from the charge pump (TC1044SCPA). The whine will change frequency if I touch the top of the charge pump or if I touch pin 7 or 8 on the back.

I have swapped out the charge pump with every other 1044S that I have, as well as trying each 7660SCPAZ I have. They all exhibit the same characteristics, with the only difference being the frequency or volume of the whine generated. I have replaced the input and output jack wires with shielded wiring, but that hasn’t helped the problem either.

EDIT TO ADD - I’m also getting some odd faint oscillation on the decay of notes on the higher frets when I apply vibrato, if that sparks any thoughts as to whether this is the charge pump or something else.

This problem exhibits itself even when the pedal is completely completely isolated (not upstream or downstream to any other pedal and on its own dedicated power supply)

Any suggestions as to what I might be missing that would explain why this problem has suddenly popped up after eight months of the pedal working properly? (Pardon some of the sloppiness of the build – as I said, this was one of my very first builds; I’ll go back and clean it up to current standards once I get this whining issue resolved).

Mike

 

[Robert]

Has anything external to the pedal changed in those eight months?

New power supply, new amp, anything?

 

[Robert]

If you want to eliminate (or identify) the charge pump as the issue...

Pull out the charge pump IC, do not install it during this test.

Hard wire your DC jack to the IC socket.

Positive wire to pin 3 of the socket, Negative wire to pin 5.


See if the noise persists. Do not daisy chain it like this, you're running it as a pure positive ground circuit wired up like this.
Also, your LED indicator will not work.


If the problem persists it is not the charge pump.

If the problem goes away I would change the filter caps (and maybe the diodes) around the charge pump circuit.

 

[mkstewartesq]

Has anything external to the pedal changed in those eight months?

New power supply, new amp, anything?

Thank you for asking, Robert.

No, nothing has really changed as far as the amps or power supplies. I did move the pedal from my Gigrig loop switcher over to a loop switcher I built - but it was working fine after that move. Once the whining started this past weekend, I moved it back to the Gigrig just to make sure the new switcher wasn’t introducing something unexpected, and there was no change. I also get the same issue whether I have it hooked up to my normal isolated PSU (a 1Spot Cs-12) or its own completely separate wall wart (also a 1Spot).

Mike

 

[mkstewartesq]

If you want to eliminate (or identify) the charge pump as the issue...

Pull out the charge pump IC, do not install it during this test.

Hard wire your DC jack to the IC socket.

Positive wire to pin 3 of the socket, Negative wire to pin 5.


See if the noise persists. Do not daisy chain it like this, you're running it as a pure positive ground circuit wired up like this.
Also, your LED indicator will not work.


If the problem persists it is not the charge pump.

If the problem goes away I would change the filter caps (and maybe the diodes) around the charge pump circuit.

Thank you, Robert! Let me digest all that and then give it a shot.
Mike

 

[mkstewartesq]

If you want to eliminate (or identify) the charge pump as the issue...

Pull out the charge pump IC, do not install it during this test.

Hard wire your DC jack to the IC socket.

Positive wire to pin 3 of the socket, Negative wire to pin 5.


See if the noise persists. Do not daisy chain it like this, you're running it as a pure positive ground circuit wired up like this.
Also, your LED indicator will not work.


If the problem persists it is not the charge pump.

If the problem goes away I would change the filter caps (and maybe the diodes) around the charge pump circuit.

Well, I tried this and not only did the whine and oscillation go away, so did a lot of other extraneous noise that I had been getting. Thank you for this incredibly helpful information.

In the schematic below, I assume that the filter caps I would replace (as well as the diode, if I do that as well) are those I have circled in red?

Thank you again

Mike

 

[Robert]

Yep, that's the caps.

I don't think I'd bother with the polarity protection diode, this one doesn't have diodes in the charge pump circuit so just ignore that rambling.

 

[spi]

The only time I had a whine in my circuit it was a bad electrolytic cap, and replacing it cured it. Hopefully this works for you. I was able to isolate the bad one because the whine pitch would change when I touched it.

 

[mkstewartesq]

The only time I had a whine in my circuit it was a bad electrolytic cap, and replacing it cured it. Hopefully this works for you. I was able to isolate the bad one because the whine pitch would change when I touched it.

C5 is the one that changes the frequency of the whine if you touch the leads – but it’s still doing that even after I replaced it.

Unfortunately, replacing capacitors C5 and C6 didn’t improve the situation any. Still a whine no matter how many different charge pump ICs I try, and the actual frequency of the whine varies from chip to chip without any rhyme or reason why. Also still slight oscillation and a lot of background noise (Treble boosters are, by their nature, noisy but I didn’t realize just how much background noise there was here until it virtually disappeared when @Robert had me try hardwiring the power to the sockets and omitting the charge pump).

So I’m still stumped. For now, I’m just using the charge pump IC that has the least obtrusive noise until I figure out what is actually going on.

Since touching the body of the IC itself (even just the black case, not the leads) also changes the frequency of the whine, I’m starting to wonder if maybe the socket is the problem although I can’t imagine how it would be. I reflowed all of the joints to the socket to be safe but that didn’t make anything any better. I’m hoping I don’t need to start snipping up the socket and desoldering it.

Thanks to everyone for the help so far.

Mike

 

[mkstewartesq]

Also – I probably should’ve mentioned this right off the bat in case it triggered a thought in the mind of someone who knows more about how these circuits work than me (which would be pretty much everyone here): the very first time I detected a problem this weekend was when I kicked on the pedal and the pedal was basically outputting sound like an octaver. (A note accompanied by a note that sounded like an octave below at the same time) After playing around with it a bit, that symptom disappeared and instead I’ve been stuck with this whining/oscillation issue I’ve discussed above.

M

 

[jwin615]

Does it whine if it's the only pedal in the chain? Two cables, 1 guitar, 1 pedal.

 

[mkstewartesq]

Does it whine if it's the only pedal in the chain? Two cables, 1 guitar, 1 pedal.

It does, yes. Two cables, one guitar, one pedal with its own power supply (not part of a daisy chain powerline). I’ve tried it with both a dedicated output on my 1Spot CS12 power supply and on a 1Spot wall wart in a different outlet (surprisingly, the wall wart was just a tiny bit quieter than the dedicated out from the CS12.

Thanks!

Mike

 

[Mobissimo]

Mike, was reading another thread & this post + following seemed related: https://forum.pedalpcb.com/threads/pro-filter-has-high-pitched-ringing.15715/#post-240597 Linking here in case it’s any help.

 

[mkstewartesq]

Hey, thanks! I actually tried the 7660s as well, early on but in my case, it didn’t make any difference. Still haven’t figured out exactly what the issue is.

Mike

 

[synthesiserror]

Re-flow your DC negative connection here, and then check for continuity between this joint and the center pin of your DC jack. It seems stupid but this sounds like a ground issue to me.

 

[Mobissimo]

Hey, thanks! I actually tried the 7660s as well, early on but in my case, it didn’t make any difference. Still haven’t figured out exactly what the issue is.

Mike

Hey Mike, sorry about that, just saw that note in your earlier post