Crumar Roadracer Keyboard Chorus?

[Arn C.]

Hello All,
    I picked up this keyboard from a friend, he didn't want it anymore.  It worked, but some of the keys didn't work.  I spent a lot of time on the keys and finally got them all working.  I put it away for a while and took it out to give to another friend of mine as her keyboard crapped out on her.
Well, hardly any of the keys worked.
    To make a long story short I gutted the keyboard.  The chorus in this keyboard sounded excellent.  It had two sliders, can't really remember which was what.  I think one said chorus or vibrato(not sure) and I believe if I can remember correctly it was like a volume.  The other one was either pitch or speed(I am thinking pitch, but I may be wrong).
Anyhow this chorus or vibrato whatever sounded really nice, so I scalped this board, but idiot me did not really follow the wires to the pots or the in and out or the power and ground, I was hoping maybe someone could help me with this so I could make a pedal out of it for my guitar.

Here is a comment I read about the chorus section:

It has a built in chorus, which is more like a flanger/phaser. At it's higher settings, it's almost an LFO.

Here are some pictures I had a friend take, I labelled all the components:




Thanks!
Arn C.

[Mark Hammer]

Well duh...it's a Small Stone.  Check the SS schematic.

[Arn C.]

Mark,
    That is what I thought, but the sound was much better than the smallstone that I have(an original with a bunch of mods)  The sliders were 2k2 and 1m.

Peace!
Arn C.

[Mark Hammer]

Possible differences may be in the sweep width and amount of resonance.  Keep in mind the SS has only two settings of each, and I gather the choices made were some sort of compromise at being all things to all musicians.  In this case, the "client" is a known keyboard, so the values may have simply been more wisely chosen.

Reverse engineer it and maybe you can find out something useful about optimizing your guitar phaser.

[Arn C.]

Yeah, what I thought was so different was the second pot.  What a difference that makes and of course no color switch.   At least now I have a vague idea of what a flanger sounds like.  But seriously, this thing sounds so cool.   Also I never took voltage readings to see what input voltage is.  Anyhow, I will take your advice and try reverse engineering it, I don't know how to use any programs to make it look pretty, so I will have to do it on a piece of paper.   I hope someone else can use this, too coool...

Thanks!
Arn C.

[Vsat]

Arn,
Was wondering about that one! Thanks for taking the pictures. Looks like your typical Crumar PCB.
Regards, Mike

[Arn C.]

Mike,
   I also gutted the rest of the boards, not sure if anyone is interested in them or not. There are 5 smaller pcbs  with  40 pin ic and 12 - 2.2uf electros, 12 diodes(maybe1n914's) ,  12 resistors(470K) and 12 resistors -(320K) and 12 - .47 100v square plastic case caps surrounding the large chip.   and a large main board with ics and tons of diodes and a few resistors(no caps).   I don't need them for anything.  If someone has this keyboard they are welcome to have them.  I think I will keep the power board tho.

Peace!
Arn C.

[Vsat]

Arn,
Probably many of the chips used in  there are also used in string synths. Top octave generators MK50240, M083, AY-3-etc), keyer/divider chips like S10430, TDA1008 etc... worth saving/making available for repairs. Certainly don't throw them out.
Regards, Mike

[thomerow]

Hello! I know this topic is more than six years old now, but I decided to post a reply instead of starting a new topic nevertheless. I think this way it is easier for people looking for the same information I was looking for to find something about the Roadracer chorus board on the internet.

Arn, did you manage to build a guitar pedal out of the PCB in the meantime? Or was it perhaps even possible to reverse engineer it? I ask because a friend of mine who is also a guitar player has a Crumar Roadracer which he isn't using much. A few days ago he stumbled over your post and told me about it, and now I am going to try and convert the chorus board to a standalone effect processor.

It would be great if you could post something about the things you found out while playing around with the board!

Cheers,

Thorsten