Basic latching relay not reliably turning off/bypassing

[markuus]

Trying to use a relay bypass for the first time in an Acrylic Overdrive (Wampler Plexi Drive) pedal I was putting together. The relay reliably turns on the effect but it has trouble turning it off/bypassing the effect. I'm trying to narrow down the issue before I just rip it out and just go with a standard 3PDT footswitch.

Basic Relay Bypass (Latching) - PedalPCB.com

Relay Bypass Module

www.pedalpcb.com

https://docs.pedalpcb.com/project/LatchingRelayBypass-PedalPCB.pdf

Here's what I'm seeing:

• When first applying power, the LED is off and effect is bypassed
• Upon pressing footswitch, the LED turns on and the effect is active. This works 100% of the time
• Pressing footswitch again, nothing happens 95%+ of the time. The effect and LED remain on. Pressing the switch dozens of times, the relay eventually switches and bypasses the effect. I can't seem to find a pattern of when it actually works- just very intermittent.
• Once off, the switch reliably turns the effect back on 100% of the time.

I didn't have a 10-pin socket on hand, so I soldered the relay directly to the board. I feel like I've seen others do that, and I was careful soldering it on, letting it sit for several minutes between soldering each of the 10 legs. Could I have fried it?

I did use a tantalum 1uf cap in place of the 1uf MLCC specified in the docs. Could that affect the behavior?

I tested the momentary footswitch with my DMM before I did anything else- I confirmed it's a normally off momentary switch by testing continuity. I had another NE555 IC on hand and tried that but same behavior. I'm using a TQ2-L-5V and I verified I'm using the right transistors, which I got from Mouser.

Anyone had similar issues, or have any suggestions?

Not the end of the world- I can just swap out for a standard footswitch if I can't figure it out, but just disappointed my first try at using relays isn't working.

 

[fig]

Did you pay attention to the polarity of the tantalum? It wouldn't be marked, but the negative pin should be directly connected to ground.

Is that a TQ2-L5V ?

Edit: It appears that the negative lead should be oriented towards the top of the PCB.

 

[markuus]

@fig nope I absolutely did not. I’ll try desoldering and flipping around. Thank you!