Could faulty 3PDT switch cause a short?

[Kroars]

So, I’ve built 50+ pedals (vast majority PedalPCB) and while I’ve had some issues during the first few, with the help of a few of you here I’ve been able to solve. I’m happy to report that the last 35+ have been “issue free” and work great (thanks again for your help!!).

Well, I’m back again with another issue. Built my 5th & 6th War Scythe (I like to build in pairs) one works one doesn’t. On the one that doesn’t, led indicators all turn on and off with each of the three foot switches but I get no sound neither in active nor bypass. I’m also getting continuity between the positive and negative terminal on my input jack when I activate footswitch.

Ive ordered 3pdt footswitches from Amazon and Tayda and have never had an issue out of the 80+ I’ve used. I’m wondering if a faulty 3pdt footswitch can cause a short and not allow any sound in active or bypass but led’s still work.
Board is very clean, no visible bad connections, cleaned well with QD cleaner, reflowed all joints. I’m at a loss.

thanks in advance!

 

[Kroars]

Meant to post this is troubleshooting... how do you delete a thread?

 

[moonlightpedalbuilds]

I never had problems with 3pdt both cheap, tayda and loveswitches with grounding. I had a problem with tayda 3pdt’s that do not latch.

Are you using solid or stranded wires? A single wire from the stranded can mess up your pedal. Check both sides of the 3pdt breakout board.

If you think 3pdt is faulty, it is time to replace both 3pdt and breakout board.

 

[Chas Grant]

If you know what foot switch is the problem, remove the ground wire from the PCB for that foot switch and then check resistance input to ground on input jack with footswitch on, also check it on break outboard between input and gnd terminals. If the jack is good and the board has continuity, its the board/switch. Its possible that the switch is sticking on the ground pole causing the short to ground. If the breakout board is like a wired setup, when the effect is bypassed the board input is grounded. If its sticking, when you activate footswitch your input will be grounded.

 

[HamishR]

It's easy enough to test a switch with the continuity test on your DMM. I would be looking at the transistor sockets. I always solder transistors directly to the board because I always have issues with the tranny sockets. Never IC sockets though.

 

[Mcknib]

The input jack tip and sleeve shouldn't have continuity as you know

The fact you don't get audio on all 3 or bypass would suggest your input jack's the problem ie no audio getting into the circuit at all, so a fault that's then having a knock on effect on the rest of the circuit, that's not to say it couldn't be something else!

Sounds like it's dumping your signal straight to ground and not into the circuit or bypassing to output jack via the switch

Your input jack solder joints look fairly close on the pcb check they don't have continuity

I'd then remove either your input jack tip or sleeve wire at the jack end and see if they still have continuity that'll tell you whether it's the jack itself or something else like a solder bridge, a faulty 3PDT etc

You can continuity check all 3 switches to make sure they function by doing the usual check - clicked one way middle common row has continuity with top row and the other way middle common with bottom row

Also check they dont have continuity to both throws at the same time ie when the middle common and top connect both shouldn't have continuity with the bottom and visa versa that'll let you know if it's damaged internally or there's a solder bridge hiding under the breakout board

Your LED coming on / off just means that particular pole is working, a 3PDT is basically 3 SPDT switches side by side

 

[music6000]

The input jack tip and sleeve shouldn't have continuity as you know

The fact you don't get audio on all 3 or bypass would suggest your input jack's the problem ie no audio getting into the circuit at all, so a fault that's then having a knock on effect on the rest of the circuit, that's not to say it couldn't be something else!

Sounds like it's dumping your signal straight to ground and not into the circuit or bypassing to output jack via the switch

Your input jack solder joints look fairly close on the pcb check they don't have continuity

I'd then remove either your input jack tip or sleeve wire at the jack end and see if they still have continuity that'll tell you whether it's the jack itself or something else like a solder bridge, a faulty 3PDT etc

You can continuity check all 3 switches to make sure they function by doing the usual check - clicked one way middle common row has continuity with top row and the other way middle common with bottom row

Also check they dont have continuity to both throws at the same time ie when the middle common and top connect both shouldn't have continuity with the bottom and visa versa that'll let you know if it's damaged internally or there's a solder bridge hiding under the breakout board

Your LED coming on / off just means that particular pole is working, a 3PDT is basically 3 SPDT switches side by side

I drew this up while Mcknib was answering so,
1. Check for Continuity on the 3 individually marked in Red, This is Bypass / Off mode.
2 You should not have continuity with the Red Centre pad & Green pad directly above it while in Bypass/ Off mode.
This applies to all 3 footswitches !

 

[music6000]

As Mcknib stated: remove either your Input jack tip or sleeve wire at the jack end and see if they still have continuity that'll tell you whether it's the jack itself or something else like a solder bridge

Maybe Solder has fallen inside the Jack & caused a Bridge/ Short.

 

[Kroars]

The input jack tip and sleeve shouldn't have continuity as you know

The fact you don't get audio on all 3 or bypass would suggest your input jack's the problem ie no audio getting into the circuit at all, so a fault that's then having a knock on effect on the rest of the circuit, that's not to say it couldn't be something else!

Sounds like it's dumping your signal straight to ground and not into the circuit or bypassing to output jack via the switch

Your input jack solder joints look fairly close on the pcb check they don't have continuity

I'd then remove either your input jack tip or sleeve wire at the jack end and see if they still have continuity that'll tell you whether it's the jack itself or something else like a solder bridge, a faulty 3PDT etc

You can continuity check all 3 switches to make sure they function by doing the usual check - clicked one way middle common row has continuity with top row and the other way middle common with bottom row

Also check they dont have continuity to both throws at the same time ie when the middle common and top connect both shouldn't have continuity with the bottom and visa versa that'll let you know if it's damaged internally or there's a solder bridge hiding under the breakout board

Your LED coming on / off just means that particular pole is working, a 3PDT is basically 3 SPDT switches side by side

Thanks for the response! The weird part is that in bypass I don’t have continuity between the tip & sleeve (but still no sound). It’s only when I activate the 3pdt do I have continuity between tip and sleeve -still no sound. This is a strange one.

 

[Kroars]

Thank you all for the quick responses! I’ll check all suggestions and get back to you with the winner (hopefully).

 

[Chas Grant]

Just an observation, the 3PDT breakout boards are raised up off the switch. Have you checked in between the board and switch for anything causing a short

 

[music6000]

As Mcknib just answered I was busy again so, When Switched to ON position, Check for Continuity on positions marked in Red.
Make sure you don't have a bridge or Continuity to Footswitch bottom pads in Green.

 

[Mcknib]

Thanks for the response! The weird part is that in bypass I don’t have continuity between the tip & sleeve

Doesn't sound like the jack if it only happens in the effects position

The in pads are right next to ground on both the main and breakout pcbs so as @Chas Grant said intially check these pads don't have continuity and visually check there's no solder bridges or wire strands bridging on the underside because obviously when you switch to bypass it breaks the in tip and sleeve connection

Hopefully it's something like that and not a 3PDT internal short if you've gone a bit gung ho with the soldering iron haha but your continuity checks should rule that out

Then there's the old toothbrush clean there is a fair bit of flux residue visible so give that a whirl

 

[music6000]

You should have No Continuity on Tabs marked in Red on all 3 footswitches.

 

[Chuck D. Bones]

It's easy enough to test a switch with the continuity test on your DMM. I would be looking at the transistor sockets. I always solder transistors directly to the board because I always have issues with the tranny sockets. Never IC sockets though.

Do you use actual transistor sockets? The DIP & SIP sockets are too loose for most transistor leads, but the tranny sockets I bought from Small Bear work great.

 

[HamishR]

I haven't seen transistor sockets except the big round ones for Ge trannies. I've had bad luck with those too! I'll check out Small Bear - cheers!

 

[Kroars]

Do you use actual transistor sockets? The DIP & SIP sockets are too loose for most transistor leads, but the tranny sockets I bought from Small Bear work great.

Thanks! No, I haven’t been able to find any proper tranny sockets. Must’ve missed them on my visits to SB, I’ll check it out.

 

[daeg]

The 3PDT sold by Tayda have given me problems. Every few clicks they get stuck in an in-between position where neither throw is making contact.

Could have been a bad batch.

 

[Kroars]

Just an observation, the 3PDT breakout boards are raised up off the switch. Have you checked in between the board and switch for anything causing a short

Thanks for the response!

I typically place them toward the top of the posts. My thinking is that it’s further away from the epoxy (hopefully helping in not loosening the posts) and also in some of the more cramped builds it’s given me that little extra space to come up from beneath the breakout board and more easily slide in the wire.

I’ve finally got some time to check it out today, hopefully I’ll find the culprit.

 

[Kroars]

Solved! Located continuity on one of the 3PDT switches where there shouldn’t be, changed it out and it works perfectly! Thank you all!!