Roland JX-8P restoration

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The LT
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Roland JX-8P restoration

Post by The LT » Tue Jan 22, 2019 7:44 pm

Hi, vintage synth fans,

While waiting for parts to arrive for my Juno-106's, I've picked up another patient to be restored. As I am a big time Roland fan and the stars were right, I've found a cheap synth in another town. That would be the venerable/controversial Roland JX-8P.

The unit arrived last Monday and I've started the clean-up process. Naturally, it had all the issues a typical JX-8P develops over the years. A few keys didn't trigger at all, the aftertouch was busted, the faders were jumpy, it had dust and grime all over it. The white keys are horribly yellowed and covered in decades-old layer of dirt.

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A couple of tact-buttons require a bit of force to trigger, but most of them work. The bender assembly was almost falling off, the screws holding it were loose. Of course, the unit is missing quite a few screws and most plastic pits in the sidepanels are destroyed.

It may sound bad, but considering its age, it's not that bad. There aren't any deep scratches on the face panel and the left slider/bender panel.

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I've started pulling the thing apart. First, the keybed was disassembled and the keys went to a bath. Oh God, I've read that SK-361 keybed is quite labor-intensive to rebuild but my, oh my. Took me a whole two working days just to give the keys a thorough cleaning, disassemble the aftertouch strip assembly and but the thing back together.

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Cleaning, polishing and putting the aftertouch assembly back together took a few hours. I haven't polished the keys themselves, I am considering a retr0brite gel method and a polish to get them back to their former glory. At least they are all from a single instrument and look consistent.

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I've finally reassembled the keybed and started the thing up. It sings! And the aftertouch is working! But... I am getting crackling on all patches. Also, sometimes there seems to be VCA glitches, the voices bleed through and there is some modulation going on the background, albeit quite at low levels. From what I understand, it seems to be an op-amp issue, but I am not entirely sure how to track it down.

I would also like to replace the faders, but it seems they aren't that easy to come by. Someone somewhere suggested to remove the shaft/brush assembly from the old ones and put them into new suitable 10k faders. But I am not sure of a suitable replacements. Most of my Roland gear either has 100k or 50k sliders.

Any suggestions? I'd like to tackle the op-amp issue first. :)

The LT
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Re: Roland JX-8P restoration

Post by The LT » Fri Feb 01, 2019 8:51 pm

Socketed and changed all the 18 dual op-amps. Some of the clicks and pops are gone but some of them still remain. Cleaned both the switches and faders. Now the level switch doesn't crackle.

Hmph... Need to dig deeper. Next in line are the quad TL064CN op amps. They are dirt-cheap so I'll just replace all of them for good measure. A fellow VS user mentioned replacing IC54 which is a TL064CN.

The LT
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Re: Roland JX-8P restoration

Post by The LT » Tue Feb 05, 2019 11:04 pm

Thanks to fellow VSE supporter synthRodriguez and his thread on the JX-8P noises, I've replaced and socketed the quad op-amp array entirely. It fixed the noise problem. The op-amps were cheap and I didn't bother with troubleshooting.

I've recapped the power supply and installed a new M5230L voltage regulator. The synth now sings and I am now a happy JX-8P owner, thanks to VSE archives.

Next up, ordering a mini PG-800 kit from retroaktiv.

Knas
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Re: Roland JX-8P restoration

Post by Knas » Tue Oct 08, 2019 9:36 am

How many quads did you replace?

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