Replacement footswitch - 3PDT for X Wing?

Beexter

Right, the switch on my RAT2 is playing up again and I've had it with the crappy X-wing type switches. Can I replace the X-wing with a 3PDT by only using two of the rows of the 3PDT switch? Or can anyone recommend a decent DPDT footswitch (and supplier).

The reason for wanting another DPDT switch is that is how it is wired (its a very early RAT2 ) and I don't have the knowledge, capability or desire to change it - I'd rather just swap everything over like-for-like but avoiding another rubbish switch! Seemingly, the 3PDT switches are easier to get hold of and seem a bit more robust. To be honest, anything has to be better than the X-wing which also "feels" horrid when you step on it.

I assume the contacts on the x-wing correspond to the 3PDT switch as follows (cue play school image again!). Confirmation from someone who knows what they're doing would be appreciated before I go in for another bout of open RAT surgery....

ICBM

Yes, that will work.

For better reliability connect the unused row of terminals to the orange row as well. Put the doubled contacts on the side of the switch which connects to the jacks.

Beexter

ICBM said:

Yes, that will work.

For better reliability connect the unused row of terminals to the orange row as well. Put the doubled contacts on the side of the switch which connects to the jacks.

Cheers @ICBM - do you mean just a little jumper running straight across ie. top middle - top right, centre - centre right & bottom middle - bottom right? 

As a total novice who likes to learn, what does that achieve?

ICBM

Beexter said:

Cheers @ICBM - do you mean just a little jumper running straight across ie. top middle - top right, centre - centre right & bottom middle - bottom right?

Yes, three little jumpers just like that.

Beexter said:

As a total novice who likes to learn, what does that achieve?

It means the two switch poles are working in 'parallel redundancy' - that means that both are doing the same job at the same time. If one fails, or makes a bad contact, it doesn't matter because the other one is still working. It would take a fault in *both at the same time* to stop the signal getting through, which is much more unlikely than either alone failing.

Theoretically, if the probability of a failure of each switch pole is (say) 1 in 10,000, that means that the probability of failure in a parallel-redundant switch is 1 in 100,000,000 - essentially zero. It won't be that good in reality because there are failure modes which can affect both sides at once - eg if the plunger jams - and if one pole fails outright then the odds of the other one going the same way even without a common factor are then only the original 1 in 10,000, but it's certainly much better.

This is why it's always good practice to wire up any unused poles in a switch - there is no cost other than a tiny bit for materials and the time taken, but it greatly improves reliability. The reason to put it on the jack side of the switch is to make the bypass path the more reliable one, since the 'on' path has other possible failures which would still stop the pedal working.

This is one of the simplest principles in failure mode analysis - you can often greatly improve reliability with very basic methods like this.

The standard wiring for a true-bypass switch would never be considered correct because it uses the two switch poles in *series* rather than parallel, which doubles the chance of failure - a fault in *either* will stop the signal getting through. The RAT is not wired like that though.

Sorry, a bit geeky I know .

Beexter

Brilliant. No need to apologise - geeky is good! Thank you so much for taking the time to explain, it's helpful and informative.