How to true-bypass an entire pedalboard upon power failure

[David]

My analog pedalboard had a catastrophic failure when I last tried to use it on Christmas Eve.  When I finally got around to diagnosing it last month, it looked like I had damaged at least half the pedals on it.  I got to thinking that maybe this was the time to finally go all the way and build the integrated analog pedalboard I always wanted to build.  But I digress...

Anyway, posit an integrated analog pedalboard.  Assume everything works great.  A feature that I want to put in is a way to automatically true-bypass the entire pedalboard if power to the board fails, thus ensuring that at least clean uneffected guitar gets out.  It seems to me like maybe I could do this with a relay.  From what research I've done, it looks like I would need a normally-closed relay, the idea being that it opens when power is applied, thus disconnecting the "power failure bypass".  I also think that I would not want this relay to latch.  So far, I have not come up with the animal that seems to meet my needs.  All the normally-closed relays of the PCB  mount variety that I've found seem to all latch.  I have found quite a few references to "general-purpose relays", but I can't deduce what sets these apart and if they might work for me or not.

Finally, I just am uncomfortable with the idea of this relay consuming power to keep a signal path disconnected.  Is there maybe another way to do this that I am not aware of?  If not, does anyone know if a general-purpose relay can be configured as a normally-closed (opens when power applied, maybe I should say) SPST switch?  Failing that, where can I get a normally-closed nonlatching relay in the United States?

[R.G.]

DPDT non-latching relays have NC and NO positions. One position is normally closed, meaning when the relay is not picked, the contacts are closed. Make your true bypass out of one of those, and activate it with power to the pedalboard. Power fails, relay reverts to normally closed.

You can get these for under $4.00 each at Mouser.

[David]

Cool!  The Master solves the problem with his usual aplomb.  Domo Arigato, Sensei.

[Perrow]

SPDT relays are $0.64 at Tayda, use two.

[R.G.]

De nada, mon frere.

[runmikeyrun]

why not a passive TB loop box?  You only need a battery for the indicator LED, and it will only cost you 4 jacks, a 3PDT, and an enclosure.  You can make them very small too.  I use one as a master bypass so when I have several effects going I can just step on one switch to immediately take all the effects out of the signal path.

[David]

why not a passive TB loop box?  You only need a battery for the indicator LED, and it will only cost you 4 jacks, a 3PDT, and an enclosure.  You can make them very small too.  I use one as a master bypass so when I have several effects going I can just step on one switch to immediately take all the effects out of the signal path.

In effect, I think that's what I'm referring to.  I'm looking for it to trip automatically if something happens with power to the pedalboard.  I don't want to have to think.  Period.  I don't know if it's age, if I have incipient PTSD, or I just went through too much stress on my last project, but now I freak out when stuff like this happens, I still have three more services to do, and I have no clue how to bring it back on line.  If I can bypass the pedalboard, I can limp through the current song and then swap in either my backup analog pedalboard (which will contain the pedals that I have left) or my digital rig.

[David]

SPDT relays are $0.64 at Tayda, use two.

Obviously the price is attractive.  Have you got a manufacturer name or a part number, perchance? And are they normally-closed?

[Perrow]

Obviously the price is attractive.  Have you got a manufacturer name or a part number, perchance? And are they normally-closed?

No manufacturer or datasheet, but as R.G. said, a Xpdt relay has one NC position and one NO just find the NC with your multimeter and wire your bypass to that.

Hold that, Tayda actually have a clear picture showing manufacturer and part number (though they might use the same picture for all four models of they stock) and they also have a link to a datasheet.

[David]

Obviously the price is attractive.  Have you got a manufacturer name or a part number, perchance? And are they normally-closed?

No manufacturer or datasheet, but as R.G. said, a Xpdt relay has one NC position and one NO just find the NC with your multimeter and wire your bypass to that.

Hold that, Tayda actually have a clear picture showing manufacturer and part number (though they might use the same picture for all four models of they stock) and they also have a link to a datasheet.

Yeah, and I looked at it.  I couldn't determine the NC/NO configuration, but this isn't a problem given what you stated above.

Thanks!

[defaced]

If I were a betting man (Form C on the last page): http://www.tianbo-relay.com/bigimg/18.pdf