Optigan Repair: Fixing Chord Buttons on the 35001
If you are like me and are lucky enough to have gotten hold of an Optigan ($40 in the late 90's, whoot!), chances are that you have had a few scratchy keys or buttons. In my case, I have had inoperative chord buttons since I've owned this thing. Not even a crackle or pop could be heard no matter how I jiggled/pressed/molested them, so I always figured the electronics or sensor had gone bad. Well to my surprise, they just needed cleaning! I can't tell you how thrilled I am to have working chord buttons, since they really are 75% of the charm and sound of the Optigan.
There's very little info out there on servicing these units (Pea Hicks site is not terribly forthcoming with the service manual), so I thought I'd give a step-by-step on how to get at those suckers. My unit is a 35001, not sure how others related in terms of assembly, but this should be helpful for anyone trying to service their Optigan. It's taken me a while to finally do this, because every time I started unscrewing things, I thought I was doing something wrong (you can see why below).
Step 1: Unscrew the back panel and remove. Slide out the top panel that holds the stand. This should slide right out.
Step 2: Remove all the screws holding the top unit in from the front.
There are two screws under the keyboard ends, one on each side:
There are another 2 screws in under the keyboard holding in the circuits blocks from the front.:
Step 3: Remove the platter spring access panel.
This is a service panel that lets you get at the springs that send the spindle up and down. It's in the way of pulling out the top unit, so just take it off:
Unscrew and remove the bracket for the front panel bar that turns on and off the drive system. Since the front opening doesn't get removed this has to be disconnected:
Step 4: Unscrew the top unit from the frame.
There are 4 screws, 2 on each side that need to come out. A socket wrench helps on these:
There are 2 screws that hold the unit in from the bottom that also need to come out:
Finally, unscrew the circuit board from the vertical block holding it in. Two screws here:
Step 5: Disconnect the amp boards and volume pedal string.
At this point the top unit is free, but you need to disconnect some things to get the unit out.
First start by removing the wires that lead from the Amp boards to the speakers. There are 2 AMP boards and 2 jumpers that need to disconnect on each. You should be able to see which are which by running the wire from the speakers:
Also, disconnect the RCA jacks that go into the reverb tank.
Now comes the tricky part: the volume pedal string...
The Optigan uses an ingenious method of controlling the volume by revealing a light sensitive resistor to the residual light coming from the lamp via a piece of film similar to the discs with varying degrees of opacity. Depressing the pedal all the way reveals the sensor completely. Unfortunately, in my case, I can't remove the string that connects this to the pedal, so I took it off the pulley to get more slack. Next time I service mine, I will cut the string and add a quick release, like a ball chain link, and tie the ends to that. I would recommend that you consider this, because it's time to slide the unit out.
Step 6: Slide out the top unit.
If you didn't add a quick release to the pedal string, BE CAREFUL. This thing is heavy and unweildy.
Slide it out:
Place it right on top of the frame:
Home free now!
Step 7: Remove the plastic top panel.
By now you can see the 4 screws on top holding on the plastic cover on, remove them.
There are also a few screws in the front:
But there are 2 other hidden screws....
The first is next to the chord buttons on the inside on the unit, you can see this by looking in from the back:
Also, a secret screw is accessible from the bottom of the unit. I removed this screw and never bothered to put it back. It doesn't seem to ground anything or make anything firmer and was too much of a pain to get back in! You can get access to it from a little hole in the bottom (I did this eariler in the process as you can tell from the photo):
Now the plastic cover can come off.
Step 8: Access the circuitry.
Flip up the plastic cover and place behind the top unit. I didn't bother to remove the cable that connects to the beat indicator/logo, so be careful here as well:
Now you can see the horror of the chord buttons, remove any dead rodents, human finger cheeses, and the rotted remains of the cushion (which by now has turned into something resembling asbestos).
Now we can unscrew the contacts from the PCB and CLEAN IT! It will still be connected via a green wire, so take caution again and flip it open like a butterfly:
Step 9: Clean it! I used a combination of electronics cleaner, deoxidizer and a razor blade. You can get the good stuff at Radio Shack. Take your time and test and re-test. It's a bit difficult to clean the contacts on the button frame (pictured to the right of the PCB ), but those are the most important. When I first heard the chords working, I nearly fell out of my chair! These were totally DOA (or so I thought), no crackles no hum, no nothing.... So that should tell you how dirty they can get.
Step 10: Put it all back and rock out!
Personally, I didn't replace the chord button cushion with anything. It's recommend to shield it from ground loop hums, but I'm not hearing anything. I've heard of using a mouse pad with the proper grid cut in it.
Hope this helped, comments and questions welcomed, especially if you would have done anything better/different.
There's very little info out there on servicing these units (Pea Hicks site is not terribly forthcoming with the service manual), so I thought I'd give a step-by-step on how to get at those suckers. My unit is a 35001, not sure how others related in terms of assembly, but this should be helpful for anyone trying to service their Optigan. It's taken me a while to finally do this, because every time I started unscrewing things, I thought I was doing something wrong (you can see why below).
Step 1: Unscrew the back panel and remove. Slide out the top panel that holds the stand. This should slide right out.
Step 2: Remove all the screws holding the top unit in from the front.
There are two screws under the keyboard ends, one on each side:
There are another 2 screws in under the keyboard holding in the circuits blocks from the front.:
Step 3: Remove the platter spring access panel.
This is a service panel that lets you get at the springs that send the spindle up and down. It's in the way of pulling out the top unit, so just take it off:
Unscrew and remove the bracket for the front panel bar that turns on and off the drive system. Since the front opening doesn't get removed this has to be disconnected:
There are 4 screws, 2 on each side that need to come out. A socket wrench helps on these:
There are 2 screws that hold the unit in from the bottom that also need to come out:
Finally, unscrew the circuit board from the vertical block holding it in. Two screws here:
Step 5: Disconnect the amp boards and volume pedal string.
At this point the top unit is free, but you need to disconnect some things to get the unit out.
First start by removing the wires that lead from the Amp boards to the speakers. There are 2 AMP boards and 2 jumpers that need to disconnect on each. You should be able to see which are which by running the wire from the speakers:
Also, disconnect the RCA jacks that go into the reverb tank.
Now comes the tricky part: the volume pedal string...
The Optigan uses an ingenious method of controlling the volume by revealing a light sensitive resistor to the residual light coming from the lamp via a piece of film similar to the discs with varying degrees of opacity. Depressing the pedal all the way reveals the sensor completely. Unfortunately, in my case, I can't remove the string that connects this to the pedal, so I took it off the pulley to get more slack. Next time I service mine, I will cut the string and add a quick release, like a ball chain link, and tie the ends to that. I would recommend that you consider this, because it's time to slide the unit out.
Step 6: Slide out the top unit.
If you didn't add a quick release to the pedal string, BE CAREFUL. This thing is heavy and unweildy.
Slide it out:
Place it right on top of the frame:
Home free now!
Step 7: Remove the plastic top panel.
By now you can see the 4 screws on top holding on the plastic cover on, remove them.
There are also a few screws in the front:
But there are 2 other hidden screws....
The first is next to the chord buttons on the inside on the unit, you can see this by looking in from the back:
Also, a secret screw is accessible from the bottom of the unit. I removed this screw and never bothered to put it back. It doesn't seem to ground anything or make anything firmer and was too much of a pain to get back in! You can get access to it from a little hole in the bottom (I did this eariler in the process as you can tell from the photo):
Now the plastic cover can come off.
Step 8: Access the circuitry.
Flip up the plastic cover and place behind the top unit. I didn't bother to remove the cable that connects to the beat indicator/logo, so be careful here as well:
Now you can see the horror of the chord buttons, remove any dead rodents, human finger cheeses, and the rotted remains of the cushion (which by now has turned into something resembling asbestos).
Now we can unscrew the contacts from the PCB and CLEAN IT! It will still be connected via a green wire, so take caution again and flip it open like a butterfly:
Step 9: Clean it! I used a combination of electronics cleaner, deoxidizer and a razor blade. You can get the good stuff at Radio Shack. Take your time and test and re-test. It's a bit difficult to clean the contacts on the button frame (pictured to the right of the PCB ), but those are the most important. When I first heard the chords working, I nearly fell out of my chair! These were totally DOA (or so I thought), no crackles no hum, no nothing.... So that should tell you how dirty they can get.
Step 10: Put it all back and rock out!
Personally, I didn't replace the chord button cushion with anything. It's recommend to shield it from ground loop hums, but I'm not hearing anything. I've heard of using a mouse pad with the proper grid cut in it.
Hope this helped, comments and questions welcomed, especially if you would have done anything better/different.
Dear lord, thank you!
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Cool, glad you found it helpful.
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I used 400 grit sand paper to clean my contacts. It worked like a charm. One difference with the 35012 and yours is that the two pieces of the PCB are held together with rivets, so the two could not be separated in my estimation. I just folded up some strips of sand paper and flossed the upper contact strips and rubbed down the center of the main contacts. Also, on my 35012 the drum triggers did not make full contact with the pads, so I extended them by gluing thin strips of credit card to the points (on the dark brown switches) in order to give them an extra mm or so. Worked great! Now I need to figure how to clean the keyboard contacts to fix that broken high E... Thanks again for the inspiration to dig in to my Optigan!
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Thanks a million. All the chord buttons now work although none of the special effects buttons work. Still trying to figure out why. I was lucky enough to find the volume sensor in the insulation rubble in the bottom when I took the back off. Figured out where it should go and Voila! now I have volume control. If you have any ideas on why the FX don't work please let me know. I
did notice that the thin metallic connections between a couple of the contacts seemed to be worn away.
Anyway, thanks for the great in-depth
guide to disassembling this thing.
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