Archives for posts with tag: Crumar Bit 99

Part one can be found here:  I’ve been doing some research on this beast and it’s been really hard to track down service info for this model Crumar in particular.  The Crumar Bit 01 is the rack mount version of this box and i have that service manual but it includes no info on how to properly calibrate the oscillators or filter board.  I’m also not sure if the parts naming even matches really because the boards are not identical within each box.

So with some hunting i found that Bob at Tauntek had posted some info on his site about the Bit 99 that was very helpful.  I don’t have a scope here so i am unable to check the digital side but the analog side it starting to make a lot of sense after a few poke and prod sessions with the tweaker!

1, I fixed the velocity sense on the key bed and it’s back to 90% of feeling good.  It’s still a little clunky in spots and i am attributing this to smoker musician damage at the moment.  I cleaned the springs and rails on the key bed with vinegar and it made a great improvement on the keys that were not striking well or without useful velocity info.  I replaced any springs that were distorted or broken with a set from an old deceased mirage key bed.  So all the keys work and behave much better.  It was hard to get the springs soldered into the right position with the right amount of tension on them.  The mirage key bed has little loops that hold them in so there’s no need to solder them.

2, I am still trying to get the scale and tuning of everything right on.  If i get the oscillators tuned nice with each other the pitch bend scales incorrectly between the two voices and sounds bad.  I can get one range ( up or down ) to work but not both together while the oscillators are  scaled properly.  It’s a bit whack a mole at the moment.

3, The mod wheel is working now.  I’m not sure what was up with that before but that gremlin moved out…

4,  All of the filters are matched decently and sound great!  I will do one more round of adjusting once i get a better feel for how it sits best and sounds the most even.  If i under cal the VCA the oscillators sound better but they leak a lot when the key board is idle.  So i tweaked it back until they just barely disappeared.

5, On other quirk is that it seemed like there was some awkward voice stealing or filter triggering problem at first but i realized that it’s only apparent at the upper / lower 1/4″ outputs.  I figured out that the headphone jack actually mutes the other outputs ( much like the juno 106S and the internal speaker muting ) and the jack / switch is dirty and sometimes doesn’t make great contact.  The Crumar Bit 99 sounds really great in stereo mode when the voices are all panning around within chords.

6, I also epoxied the right end of the key bed as it had cracked.  This should help it from getting any worse.


Side note: There is also a soft version of the Crumar Bit series Here:  I haven’t tried it though…

::: IF :::

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!


::: IF :::