Another "noise problem" thread. BB Preamp inspired build...

[bendeane]

Sounds fantastic when it works and my tweaks to the circuit puts it right where I want it. When engaged, it's quiet as a BB except for when I bump on the enclosure. It seems to pickup and amplify the bump or knocking on the box with my knuckles or any other object I tap on it.

I also get a lower frequency hiss or whitish noise sounds occasionally when I play it, then bypass it, then switch it on again. No signals seems to pass but if I bypass-engage it a few times it goes back to working as it should.

Also have the "popping" when I engage the switch but I'm wondering if that is tied to the amplification of tapping on the enclosure. It could be the physical sound of the switch being amplified and not a pop that usually gets asked about in these cases. The LED is wired up straight from the power source and not after the filtering I've put into the circuit. The anode is tied directly to 9V through my 3PDT daughter board and the cathode is run to the limiting LED and then to the switch.

I might try to upload a YouTube video upon request but if anybody has experienced the above before and has some insight in the meantime, please let me know.

Thanks!
Ben

[thermionix]

Sounds to me like a loose connection, likely a cold solder joint.  I see a few possibilities in the photo.  I would re-solder the the PCB attached to the foot switch.  On the jacks it looks like black wire is solid core untinned copper, is this right?  It's suspicious that it didn't get tinned when soldered to the jack.

ETA:  Always good to lightly poke around with the tip of a chopstick or something similar.

[bendeane]

Yeah, that black wire on the jacks is solid core not tinned. I only used it on the two jacks' sleeve to 3PDT daughter board. I also wondered if I didn't get enough solder on that board to the jack lugs. Those seem to take so much solder to get them completely covered. Do you think loose connections, cold solder joints would account for the circuit amplifying the acoustic sounds of my physically tapping and knocking on the box?

[thermionix]

Do you think loose connections, cold solder joints would account for the circuit amplifying the acoustic sounds of my physically tapping and knocking on the box?

Absolutely, and the intermittant noise you're hearing.  The solid core wire is likely oxidized, and not taking solder well.  You can hit the stripped end with fine sandpaper or steel wool before soldering and get it to work.  Chopstick time.

[bendeane]

Awesome. I'll recheck all that tonight and see what happens. With each build, my off board wiring stiff gets a little cleaner. It's got a long way to go though, obviously.

[GibsonGM]

Are you SURE it's not a microphonic tube??      Ha ha.


Nice looking build, and I'm sure Thermionix has hit the nail on the head - it'll clean up for you and likely stop being buggy! 

[MrStab]

I also get a lower frequency hiss or whitish noise sounds occasionally when I play it, then bypass it, then switch it on again.

^there's still that to address.

if it isn't related to the other problem - maybe hitting the switch jostles the dodgy wire slightly - then that sort of thing sounds to me like a cap going awry. AFAIK it's mostly ceramic caps that go microphonic, and i can't see any in your pic, Ben, but a quick Google does suggest other caps can be prone too.

maybe they're separate issues, but if not, there may be 2 clues pointing to a potential cap failure. if the 3PDT grounds your input, that could be what fixes it temporarily. i don't think you should worry about the switch popping until the other two problems are sorted.

how well-insulated is the bottom of the board? how much can it move around (if at all)?

[bendeane]

The pcb for the switch is designed to ground the input.

The board sits on the pot dust caps.

I removed everything, and I think the problem lies in my pot solder connections or the connections from the pots to the vero. I've done so much reboxing of this board that I may also have broken some of the wires on the lugs of the pots. I was able to get the "hiss" to come and go by rapping on some of the pot knobs.

I can post a pic of the solder side but I've got three vero boards with all the cuts ready to populate so I may just go at it again and use the new precut and tinned hookup wire I got in. I think the cheap hookup wire I've been using is an example of "you get what you pay for" kinda thing.

When I resoldered the switch pcb, I was using some old thicker solder than I usually use and it seemed like rosin was going everywhere. Is that a problem and if so, what's the best/easiest way to clean that up?

[thermionix]

The rosin flux doesn't matter, except for cosmetics if you care about that.  It's non-conductive and not corrosive like acid flux.  You don't want any going into a pot, that's about the only place it could cause a problem.

With the pot/hiss issue you mention, it could be the solder connections at the pot lugs, it could also be where the lugs mount to the wafer.  Sometimes, often when overheated, this physical connection can go intermittant, and pot replacement is the only solution.  Happens more with smaller Alpha and similar pots than with larger CTS or NOS pots, which are just made sturdier.

Back to the chopstick.  Get as much physical access as you can with the pedal on and plugged into an amp.  Gently rock each capacitor on the board, one at a time.  Wiggle wires, tap the ends of the resistors and lugs of the pots, eventually I think you'll find an offending connection or two.

[bendeane]

Thanks for all the replies. Today is my day without the kids so I can crank things up and test a little more thoroughly than I can during the late night hours when everyone is asleep. I'll keep you posted.

[bendeane]

Everything I touch gives me some sort of amplification of the tapping of the circuit.

[bendeane]

And I just broke off the board input connection to the switch PCB. That may have been the biggest culprit.