Archives for the month of: December, 2013

So the Juno 106 from here came back to the bench over the holiday.  But not because it had a failure again!

The band noticed that sometimes the patch edit lights would come on even if they hadn’t adjusted any sliders.  When it did the LFO would turn up to maximum and make the VCO all out of tune.  Of course when they came to drop it off we couldn’t get it to happen, so i decided to try again later.  When i did so i noticed that if i picked up the front left corner of the synth the problem would suddenly appear like clockwork.

I opened it up and reseated all the cable harnesses.  I also decided that the problem wasn’t really an issue with the electronics but the chassis.  The end cap screw mounts were all in need of some love.  I had replaced the screws but if this was to be a reliable instrument i needed to modify the way the chassis fits together.  I decided to drill out the original screw holes on the bottom row of the end cap mounts.  This would allow me to install bigger screws that fastened with a star washer nut instead of relying on the thin steel bracket that was stripped out.

I also decided to fix the right back end cap hole as it was partially shattered.  My fix doesn’t look pretty but it is on the inside so no one will see it anyway.  I used small cuts of tooth pick and epoxy to strengthen the cracked mounting hole and rebuild the missing chunk to support the new screw properly.  I was unable to use the new screw and nut fasteners on the front right end cap hole because that nut would be under the keyboard and impossible to get back off.

Oh yeah, i almost forgot!  I tracked down some shallow IEC connectors and replaced the silly 2 prong Roland one with a properly grounded 3 pronger!

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What an odd beast.  I remember seeing one back in the 90’s at a local music store.  Remember those!?  Although the price was right I didn’t buy that one because it had lost it’s memory and was full of nonsense patches.  This type of problem makes many of these old instruments seem catastrophically scrambled.

But upon inspection the scramble has a surmountable solution.  You can replace the battery and either sysex dump or tape dump the patches back in and often you are good to go.

The real issue with the more rare instruments like this one is availability of service info.  For instance it’s easy to find ( almost ) any Roland service manual to trouble shoot a synth but Crumar and many rarer instruments can be mysterious about their ailments.

What are the power supply voltages supposed to be?

What was the final OS version?

How do i calibrate the voices so that they match and perform properly?

These are the mysteries that lie beneath the hood of this Crumar Bit 99.  It’s built like a tank. The metal chassis is rugged and fully hinged like old Roland synths.  The voices are all firing ( nonsense at the moment ) and the display is working.  There are some messed up keys that i am still sorting out.  Some were broken but i used epoxy and toothpick pieces to reattach the hooks and re enforce them.  The other key problems have to do with triggering properly and triggering with velocity.  That’s right!  this synth has VELOCITY on the keybed.

That my friends is why this is an awesome instrument.

It’s much like the old Ensoniq Mirage keybeds which i have fixed many times in the past.  There’s a spring that is stretched through a window at each key.  The spring moves from one contact to the contact on the other side when a key is pressed.  The CPU determines what the velocity of the key press was from the way the spring travels across the divide.  Pretty raw and clunky but it does work as long as the contacts are clean and the springs are not mangled.  Several of the springs are really mangled and barely working on this keybed so i am going to go scavenge an old parts Mirage keybed for springs.

But i have been unable to get the tape dump to take.  It fails half way through.  There are error codes that come up but without the service manual i don’t know what they are!  The manual doesn’t list any user issues or troubleshooting info.  It’s otherwise a fairly well laid out user manual though!  I do have a sysex dump of the patch info and i will probably resort to that.  I read somewhere on the net that people have issues with the tape inputs on these so maybe this one suffers from that too.  I imagine it’s lumpy power or old capacitor related interference.

There will be updates!

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Astronaut sprint

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The usual suspects!

Linndrum, Simmons SDSV

Arp2600, SCI pro One

Roland Jupiter 6

Oberheim DPX-1

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Sexparty hits the season with another sex song!

True to form!

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I’ve never seen this perspective of Rush’s Synth setup back in the day.

Ton’s of Modular Oberheim and a Moog Taurus…

But there’s a cute Roland Tape delay hidden underneath as well!  Not to mention the Oberheim Sequencer!!!

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Rush Geddy Lee Synth Rig

Rush Geddy Lee Synth Rig

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