[sdiy] Odp: Juno 60 memory button carbon contacts

Roman modular at go2.pl
Sun Jun 26 05:50:29 CEST 2016

There are 3 things you can do:   A. 
scrub a pencil over sandpaper, then rub the conductive rubber of the 
button on this scratchpad. The button will work as new, but probably you
 may have to repeat the procedure after few years.   B.
 replace the conductive ribbon disk, as you suggested. There are sets 
with a bunch of new disks and little silicone tube, sold as 
remote-fix-kits or something like that. Cut the old one, glue the new 
one. This should work longer   C. insert a 
transistor in the way of button sensimg. Cut the connection from button 
to pullup resistor and insert PNP there. Emmiter to the micro and 
pullup, collector to GND, and base to the button. This will give another
 40 years of operation, until the rubber becomes totally useless   Roman  Dnia 25 czerwca 2016 12:05 Rutger Vlek <rutgervlek at gmail.com> napisał(a):
                  Dear list,   I'm struggling with repairs on the memory buttons on a Juno 60 which had a serious couple of decades of stage use. It's basically key cap, a holder a pair of contacts and a silicone-carbon disk contact system (dome shaped). I managed to get most of the buttons back to life, but a few of them are not working along. I cleaned the contacts in the switch (cotton stick and a bit of contact cleaner), I cleaned the carbon disks with alcohol. After several attempts I'm still measuring difference in the resistance of closed switches (nearly 0 ohms for those that work well, approximately 50 ohms for those that don't). The silicone of the domes seems to be in good shape. The carbon disks showed some grooves that mirror the contacts. After several failed attempts, I very very gently sanded a slight bit of the carbon disks to make them completely flat again. Still no improvement...   I'm looking into alternatives now, considering:   (1) finding replacement switches of the same time or replacement carbon-disk-domes. Neither showed up on thorough googling.  (2) buying new sealed tact switches. I found switches that fit the PCB, but can't find appropriate square caps that fit the dimensions (14.3x14.3) as well as being more or less the correct height.  (3) more cleaning? replacing carbon disks with ones cut off from a remote control? using carbon paint? using a pencil to add carbon? neither of these seems to me a reliable long-term solution   Any thoughts?   Personally, I'm surprised 50 ohms is not low enough to trigger the detection of a closed switch.   Regards,   Rutger   ps. Additionally, I'm looking for a missing Arp switch cap (orange, 3.2x3.3mm plunger clamp) and 8 fader caps. If anyone has those (or Jupiter 8 slider caps, which are identical) at a decent price?    ______________________________  Synth-diy mailing list   Synth-diy at dropmix.xs4all.nl  dropmix.xs4all.nl dropmix.xs4all.nl
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