From Kerry Sent Tue, Jul 17th 2018, 14:25
From Kerry Sent Tue, Jul 17th 2018, 14:25
Fantastic, great work, Kenny - this is one of the best reasons I subscribe to AH. My rescued JP4 may need these someday - it's great to have this info & experience documented. -----Original Message----- >From: Kenny Balys <xxxxx@xxxxxxxx.xxx> >Sent: Jul 17, 2018 2:01 AM >To: analogue <xxxxxxxx@xxxxxxxxx.xxx> >Subject: [AH] Jupiter-4 50K Frankenslider Install Notes + Photos (public domain) > > >Jupiter-4 Frankenslider Install Notes >-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- >17.07.2018 kennyb * Public Domain * > >This is a little bit of commentary to support the >photos included here afterwards. > >These words and associated photos are public domain and can >be used for any purpose whatsoever in perpetuity. > >Acknowledgements: >-=-=-=-=-=-=-=-=- >All of this is possible because of a description, BOM and board >design from "Homemade Polysynth". This is the link to his >description: > >http://polysynth.tumblr.com/post/84043081480/replacing-roland-jupiter-4-slider-potentiometer > >No one, in their right mind, would want Frankensliders in their JP4. >Unfortunately, there are no replacement 50K sliders available for >the Roland Jupiter-4 and when they fail there is nothing else >at the present time. > >There are seventeen 50K sliders on the JP4. The other 3 are absolutely >irreplaceable right now. The irreplaceable ones are ARP RATE, >LFO BEND and DELAY TIME. > >My Jupiter-4 had some greasy, oily goop in all of the right hand sliders. >They started to fail last year and then quickly got worse and worse. >By the end, there were dead zones in the filter cut off and flaky >behaviour with the envelopes. Some previous owner had sprayed some crap >into the machine. > >So I needed to replace all the of 17 50K sliders. I saw Homemade Polysynth's >plan and board designs to implement Bourns PTA3043-2010CIB503 50K sliders >using 2 daughter boards, pins and spacers. > >I ordered everything from OSH Park board fab, DigiKey and Mouser. >See the "Homemade Polysynth" webpage for ordering data. > >The photos should be self explanatory. This method works. You will have >a working Jupiter-4 with silky smooth sliders again after this. Pay heed >to the two issues listed here. > >Start by building the 17 sliders. Make sure that you get the spacers >in the board sandwich as flush as possible. This is not easy. Take your time. > >After dismantling the JP4 and replacing the sliders there remain 2 issues >before you will have a working synth again. > >First Issue: Major >-=-=-=-=-=-=-=--=- > >- the outer pins of the Roland 50K sliders are connected. These self >made stacked ones are not; they make the 2 connections on the bottom > and 1 on the top. >The upper most is N/C. This is totally fine for 16 of the positions >but the VCO LFO MOD slider is connected via the top, not bottom. >This problem drove me nuts for hours! When I found it, it was so >obvious. >(upper means the up direction when facing the opened JP4, > looking at the back of the slider boards) > >Solution: jumper the top pin to the bottom pin > >Second Issue: Minor >-=-=-=-=-=-=-=-=- > >- the stacking of the potentiometer is meant to level the shoulders >of the knob shaft with the originals, this is great as visually, from >the outside, the slider caps are all level. >The problem is that it is near impossible to get the exact 2.53 mm >spacing between boards as solder tends to fatten the pins and push the >spacers out a little bit. Also, the tolerances are such that the >sliders sit a little bit higher than they should and bash metal. >It needs a tiny bit of a spacer to avoid banana'ing the boards when >they are fastened again. > >Solution: I used self adhesive cork about 1.5mm thick along the entire >fastening rail. This gives the amount of lift needed. > >Conclusion: >-=-=-=-=-=- > >My Jupiter-4 works perfectly now. The sliders had been getting worse for >a while. There was nothing else I could do but this. Now I can play again. >The Bourns sliders are smooth and appropriate to the JP4. >I am very grateful to Mr Homemade Polysynth. > >Download link for photos and this text: >-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- >http://www.beatkamp.com/downloads/JP4_Frankensliders.zip