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Electronics => Beginners => Topic started by: Rjc987 on June 17, 2021, 05:17:05 pm

Title: Non-standard Potentiometer with on/off
Post by: Rjc987 on June 17, 2021, 05:17:05 pm
Hi all - I’m trying to replace a pot with a broken stem in a piece of equipment but it’s unusual. It’s 500k, about 300 degree with a hard snap-action “on” detent at the beginning of travel, which is all pretty normal so far BUT… every pot I’ve found so far has the normal 3 terminals for resistance PLUS 2 extra terminals on the back for the on/off functionality. This one only has the 3 normal leads which are arranged as expected and that go open circuit when the pot is switched off. I cant for the life of me find the right search terms to find a replacement. The markings on it are custom (pc1313x1) and only point you to the manual and suppliers of the whole board assembly (see attached) who mention that the part is obsolete and out of stock (very helpful…). Any ideas?
Title: Re: Non-standard Potentiometer with on/off
Post by: drvtech on June 17, 2021, 05:46:34 pm
Can't you just use a standard switched pot (with the extra switch terminals) and connect the switch in series with the wiper?
Title: Re: Non-standard Potentiometer with on/off
Post by: bob91343 on June 17, 2021, 06:14:14 pm
You need to disconnect all three terminals when the switch is open?  Maybe you can alter the circuit to use a single pole switch.  I think, also, that there were some double pole switches that were on the back of pots in the old days.  If you can find one of those you are home free.  Else you can add a relay to do the job.
Title: Re: Non-standard Potentiometer with on/off
Post by: Rjc987 on June 17, 2021, 10:16:51 pm
Ugh, thank you @drvtech - I feel like a total moron. I was measuring everything in circuit and assumed the two big soldered lugs with continuity were just case grounded tabs for mounting. I didn’t even consider they were doing that all along, or think to check it in the “off” position. 🤦🏻‍♂️