Tuning & Servicing an RMI Electra Piano
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- Опубликовано: 25 авг 2024
- This is an RMI Electra 300A, but the service manual I found is for a 368x, so this method should work for all RMI Electra pianos. Probably not true though for Rocksichord and even earlier models like the RMI Lark and Explorer. This video shows how to get it into tune, and I also talk about hum and sustain problems.
Service manual download: dannix.net/lib/...
This is an "electronic" piano that not many people know about compared to a Rhodes or Wurlizter electric piano, but in the early 70s it was commonly used by touring musicians who didn't want to travel with a full piano. However there are some notable exceptions of when an RMI was used in the recording studio: "Dream On" by Aerosmith, "Hello, I Love You" by the Doors, and "Right Place, Wrong Time" by Dr. John, among many others.
Rick Wakeman used an RMI electric piano and RMI rocksichord electric harpsichord on many of his solo albums and on several Yes albums.
At 2:48 - the "super old-school transistors" are in fact inductors (a coil of wire like one winding of a transformer). Each note has its own oscillator, consisting of a transistor, an inductor and a capacitor, forming a tuned circuit . This is basically a single transistor amplifier tuned to make it feed back at a particular frequency. You can not measure the "resistance" of a capacitor, since it will be infinite if working and zero if shorted. What you are seeing is the DC resistance of the inductor, which is in parallel with the capacitor.
Why not buy (or make) a sustain footswitch? It is just a single pole normally closed, push-to-break switch
That is good to know, thank you!
Large electrolytic capacitors you can sort-of measure with an ohm meter. With the cap discharged it acts like a short circuit, and then as it charges up the resistance slowly increases. It doesn't tell you much (other than that it still behaves like a capacitor). With smaller caps it simply charges too fast for a multimeter to see it, and it will indeed measure open circuit if it is okay.
@@plonkster Thanks you, that helps, that's what I was trying to measure but I didn't know it would not be helpful for caps that small. And now I have a new problem, one of my notes suddenly went dead. The service manual has a step-by-step for how to diagnose a dead note, I just need to go through it. And I discovered that the large fiber board with all the caps and pots can be lifted up and open to reveal all the keying circuits for each note! Hillarious that I didn't realize that while making this video. I think I'll make a 2nd one to show how to fix a dead note. I also want to re-wrap the chassis in new tolex, and rethink the sustain mod. Subscribe to get that new video!
I love these RMI individual oscillation per key pianos. I’ve been dreaming up a way to add touch response and midi to run two pianos at once without running some absurd cabling.
This video is an excellent reminder to never, ever let you near an Electronic Keyboard.
good job interesting video
Tony Banks of Genesis used the 368X and had his engineer mod internally an MXR Phase 90/100 pedal. It was considered a road-worthy replacement for an actual piano when traveling for live shows. Not as good as a real piano, but in a pinch. My recommendation is go ahead and recap the whole thing. Capacitors do go bad and there were a number of them that were just poorly made.
the capacitor on the A key fixed itself. when old caps sit for a long time, the insides kind of separate, and it can take operational time to "reform" them. sometimes they don't reform though, or it can take a long time and you have to slowly creep up on the voltage. you can do a search for how to properly turn on old devices with a variac
These aren't electrolytic capacitors and can't be "reformed" that way. Reforming refers to restoring the layer of oxide that acts as a dielectric in an electrolytic capacitor.
(The ones that can be reformed are the big nasty capacitors in the power supply that you really shouldn't mess with unless you know what you're doing.)
@@WolphTunes i thought they were electrolytic
@@briangoldberg4439 Nope! The dead giveaway here is the "MYLAR" printed on the side; that's the dielectric. It's just a brand name for a type of polyethylene terephthalate that's stretched out really thin.
Film caps
Cool video quite interesting 👍🏼
If there's hum, then I'd be willing to bet there's electrolytic caps in the power supply that could probably use replacement. However, the voltages can be high in those, so be careful - discharge them before touching them if you do replace them yourself. Just do your homework and everything should be fine.
Great to see you post more vids since the body swap stuff. Is the car still around? Any new bike stuff?
The imperfection in tuning inherent in the RMI electro piano really adds to it’s vibe. This imperfection all but disappeared in divide-down synths and organs, and even some modern electric piano plugins which are otherwise great are setup with exact, perfect octaves and tuning across the range, which to me makes them sound somewhat sterile.
Absolutely! This is why I have been trying to run two RMI pianos at once !