Repair question

[gotw]

New here on the forum. I have a question about DIY repair, not building. If it is not appropriate for me to ask here then please let me know.

I bought a used MI Effects Boost 'n Buff v3 and the the pedal "pops" whenever the 3PDT switch, which controls the boost functionality, is toggled. I tried several amps, in front of the amps, in the effects loop, in different order in the signal chain and it always pops when toggled. I understand that 3PDT switches can store charge, like a capacitor, and release the charge when activated. I've also heard this should only be caused when there is a buffer in the chain. Well the Boost 'n Buff has an always-on buffer, but I'm sure this is not proper behavior because it is unusable. I  have been told I can try to "clean" the pedal but how/where? Any advice for trouble-shooting this would be appreciated.

Thanks!

[Govmnt_Lacky]

Most likely... your problem is either one of 2 things:

1) There is DC being switched when the footswitch is pressed. Check the switch lugs with a multimeter (all lugs) during the switching process and see if any voltage occurs.

2) It is a mechanical problem and you need ot replace the switch itself.

[PRR]

This is not new.

Look up top.

"pop"

> switches can store charge, like a capacitor

The charge on a switch won't "pop".

Many places a switch goes to/from have a capacitor.

Caps leak. If you leave one end disconnected, they will leak-up to the voltage on the other end. When you connect, POP.

> should only be caused when there is a buffer

Over-simplified.

A naked passive guitar into a classic tube amplifier, there's no steady voltage at either end, no pop. But nearly everything in your "chain" has steady DC voltage inside and capacitors in and out.

[thelonious]

If this layout is correct, then a standard anti-pop (pulldown) resistor is probably not going to help. Here's what I'd do, in this order, checking after each step to see if it fixed the problem:

1) reflow all the solder joints where ground wires are connected and also on both ends of the other wires connected to the switch (where possible).

2) replace the 1uF capacitor connected to the switch with a 1uF poly cap like http://smallbear-electronics.mybigcommerce.com/topmay-tmcf07-5mm-box-68-mf-1-mf/ or http://smallbear-electronics.mybigcommerce.com/sec-mpc2s-1mf-50v/ (depending on which fits better in your layout)

3) replace the switch (Smallbear has those, too)

The reason I'd do this stuff first instead of trying the usual suspects like the pulldown resistors and LED anti-pop methods is because this circuit doesn't look like it should pop unless something is wrong. Also, people don't seem to be complaining about these popping in normal operation.

I've never seen a gutshot of this pedal, so I can't tell how easy these steps will be. If it's turretboard construction like the tagboardeffects version, it should be pretty easy. If it's PCB, it'll be harder bc you'll have to pull the board.

If you open it and post some clear photos it will be easier to help.

[thelonious]

Btw, since there are multiple versions of this pedal, the layout I posted might not be based on the same schematic, etc. Hence the need for pictures.

Also, just to warn you, pops are complicated. You'd think they'd be simple to fix, but there are many causes. For instance, I built a bunch of pedals for a guy who consistently reported popping problems with them when he put them on his own board---but they were pretty quiet on mine. We went through all sorts of things - pulldown resistors, LED pop softening, new switches, better switches, examining his other pedals, recapping his amp and trying different v1 tubes (yep, for real. it was a 1967 princeton and badly needed the work done anyway). You know what it turned out to be? His terrible Joyo power supply. When he replaced it with a good VL supply, no more pops. Why would someone buying tons of custom pedals and owning a 1967 Princeton be using such a cheap power supply? Beats me.

Anyway, I tell this story just to say... it's complicated.

[gotw]

I am trying to replace the 3PDT switch but I have no idea how to un-solder the switch from the board. It looks like all nine lugs of the switch are soldered to the board rather than using hook-up wire, so all nine lugs would have to simultaneously melted with my iron. Any suggestions?
Thanks

[ubersam]

...so all nine lugs would have to simultaneously melted with my iron.

You don't need to desolder all pins/lugs simultaneously. You'll need a solder pump to suck away the molten solder as you desolder each lug one at a time.

[mcknib]

As Sam says solder sucker

[gotw]

Ah OK. Thanks!

[mcknib]

3PDT's aint the easiest thing to de-solder so take your time and be careful not to damage any traces etc.

What I usually do is get rid of as much solder as I can then once it cools a little, try wiggling the switch gently to see if it's moving freely you'll see the lugs begin to move and it'll help you to see which one's aren't moving and need a little more de-soldering be careful not to apply too much heat because the switch lug insulation / epoxy can soften and push the lugs into the switch. Good luck with it I hope it all goes well for you.

[Jdansti]

What they said. Go slow, but don't overheat the switch. Allow 15 seconds or so between terminals to give them time to cool a little. Keep your iron clean. Don't try to use the iron to scrape the PCB pads or switch terminals. Just use it to apply heat.  Sometimes you have to tin the iron with a little solder to get good heat transfer.

[gotw]

I should have waited until I read these suggestions. I am pretty sure I applied too much heat. And didn't wait long enough between de-soldering lugs. The contact rings under the solder even came off but still the switch won't budge at all. I am all in at this point so I will try again tomorrow.
Thanks all.

[Jdansti]

We've all botched up boards and components. It's kind of a right of passage. 

[GibsonGM]

Just to add to what's been said - there are little plastic 'waxy' blobs around each lug...once you start melting them, you are risking ruining the switch!   That's why the 'go slow' and be patient advice.   You want those 'blobs' to be nice=looking when you finally get the thing off there    


Clear the solder, then 'heat all the left lugs fast and rock a little'...then the same to the right, then the middle, then left again...and so on...keep yer iron clean so you don't ADD solder back into the game....

[gotw]

Actually, I don't care about ruining the switch. I am removing it to try to replace it with another one. I am worried I ruined the board though.
Thanks

[mcknib]

I should have waited until I read these suggestions. I am pretty sure I applied too much heat. And didn't wait long enough between de-soldering lugs. The contact rings under the solder even came off but still the switch won't budge at all. I am all in at this point so I will try again tomorrow.
Thanks all.

Once you've got the switch out you can always continuity check the connections and if the worst comes to the worst and there's no continuity you can hard wire them.

It would be a good idea as already suggested to post some pictures.

You will get the switch out it just takes time and patience just keep removing the solder let it cool remove some more and eventually it'll come loose.

[gotw]

It would be a good idea as already suggested to post some pictures.

Does this forum host picture uploads? I don't see an upload link.
Thanks

[mcknib]

You'd need to upload your pictures to image shack or a similar site then use the insert image icon to paste the image url in.

[gotw]

Here are some images of the board with the unyielding switch:






Thanks

[Jdansti]

Are you using a solder sucker?  If so, hover the tip of the sucker over the joint, heat the joint and then quickly place the sucker tip over the joint and press the button. Try to get the switch terminal up inside the sucker tip. It will take several iterations to remove all of the solder from each terminal.