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Glad the pics are of use. I am not sure if this is a 930, there is no identification plate to be found. I have the control box on the speaker handle just as a convenient place to put it until it gets properly attached to a piano. I am guessing there are two input possibilities on mine? There is another metal box i found loose in the case that has a 1/4" jack with what I assume is a volume potentiometer that is wired to the side of the amp case. There is also the round "amphenol?" plug with cable I assume is a direct connection for the piano. I have not reviewed the schematics to confirm anything yet. I am not an image expert, but I will try and add some better quality photos.

Wow! I have looked for info on these in the past, but never found much until I ran across this post. Really neat to see schematics! Here are some pics from mine if it helps you out. Sorry if I attached too many.

That looks like a KMC1 piano lid to me. It is usually attached to a student piano with a wood verneer body.

Thanks Alan,
Hope the info on the adaptor helps. I appreciate you sharing your perspective on the MXR Smart Gate. I may have to try that. It would be nice to replace the 9v battery with an ac adaptor and still keep the low/no noise benefit. I've wasted so many 9v batteries forgetting to disconnect the battery/turn off the clav after playing.
Vance

Not sure what the original size was, I have been using an old "RadioShack" size K adaptor on mine when I dont have a 9v battery handy. O.D 5.0mm I.D. 2.1mm
It seems to hold pretty good without falling out.

Vance

Congrats!

Correct Steveo,
It's a 700, I can't even say it was a dyslexic mistake
I'm slipping, oh man!

Sorry if my post misled anyone.
V

A little late to chime in, but happend pop in after a while and saw this post. Mine is sitting in front of me. As Steveo and Cinnanon said, lower left and it is an aux out. No other jacks I am aware of on mine.

Wonderful! I would be interested to to.know and see more of the detail on how you built this and what you used to amplify it! Thanks for sharing.

Ok, I finally got around to ordering my copy. It arrived today and I thought they had shipped me a box full of bricks, this book is so heavy! I found out the weight is because of the intense amount of information and endless beautiful pictures of some pretty amazing and rare keys. It is obvious to me that there was a lot of time, thought and effort put into this. Thanks for all of your work putting this together, I know I will be spending a lot of time enjoying it's contents!
Vance

One last thing you can try before dropping more money/effort into it is the two 1/4" aux input jack's on the power amplifier. They sometimes develop continuity issues and can cause wierd things.

My simplistic understanding of them is as follows:
When plugged in, they bypass the harp input and pass the signal from your 1/4 line.
When unplugged, the two metal contacts in the plug are supposed to reconnect and pass the harp signal again.
Simple thing you can try is just plug and unplug a 1/4 plug into each one and see if the sound changes or, more desirable, goes away.

Great info Tim! I forgot about the hot glue support on those. That is really good practice. if you are already in there, you might as well make it so that it is less likely to occur again.
I don't like to admit it, but I have destroyed probably more than my fair share of traces due to lack of experience and use of cheap/incorrect irons and solder types. Way back when, of course, haha! Point is, you dont want to learn the hard way on your good, and or, hard to replace equipment!

It might be worth it to re-flow the solder on the 6 and 8 pin connectors mounted to each of the two amplifier boards of the power amp. These are notorious for causing issues like you are experiencing. This would also be in line with OZDOC's suggestion of possible loose components. You might want a tech to do it, bad soldering jobs can cause more damage if you are not familiar with soldering circuits.

Sorry to hear that didn't fix the issue. If you continue to try and fix it,  I would verify that the power supply is now giving you the correct voltage output to the piano and with minimal ac ripple. Other things you can check are if liquid was spilled in the keyboard. Sometimes cola or other liquids can play with connectivity on traces or cause bad traces. Many many things can lead to odd issues and you can find yourself wasting time and money very fast. Have fun playing with it or run away fast if you are already not too deep into it. Hope it works out for the best.
Vance

Interesting to see pics of the insides of this model. I always wondered if this model had strings or not, now I know. Unfortunately, there is no easy answer for fixing something like this. I feel pretty safe to say that you should replace the large filter caps on the power supply, simply because if it's age. They can appear ok, but still be way out of tolerance. Dirty power can cause odd behavior such as what your video seems to represent. The filter caps alone may cost you more than the piano may be worth though. That is where I would start the jurney if it were me. Thanks for sharing the pics and info and hope you find an easy fix for it.

Yes, I have seen the individual passive pickups on the Elepian. I really like the sound combo of the rhodes style pickups and wurly type reeds. I believe I have heard yours on another post and it sounded amazing!
It appears the Denon Columbia may have an active pickup like my Maestro. The action appears very similar on both, so, it would be interesting to find out more about it's amp.
I agree that the action parts seem fragile on these, so I completely understand not wanting to jeopardize them. The 3d printing idea is really interesting and would be amazing if it could help keep some of the EP's going that might not have replacement parts available otherwise.

It looks nearly identical to the U.S. Maestro version of the piano as well. Any pics of the amp? If your schematic is missing, I may be able to help you there if they are the same design.
If the plastic action parts were measured for 3d printing, that would be a neat thing for keeping these little pianos alive. Best of luck on the project!

The volume pot doesn't do much more than turn the unit on on my units. The volume increases a little bit, but mostly stays at what I would consider a mid to high(ish) level. I remember someone else commenting on theirs behaving the same . As far as what is wrong, that could be anything at this age. Typically capacitors are well past their expected life, so I always look there first, especially on the voltage regulation portion of the unit. Others may argue, but I believe in replacing all the electrolytic caps just because they are way beyond their expected life.
Let us know what you find!

Also thought I'd mention, if the piano is not producing sound from the amp, the amp most likely needs attention. I replaced the caps in both my 612p pianos. They both had issues in the voltage multiplier circuit. I replaced all the caps just because they were most likely well past their expected life. These are just like wurlies and have high voltage across the upper rail, should be somewhat low current, but be careful regardless.

Sent you a message, but here are some pics that might help. The lid slides backwards after the two wingnuts are removed. There is a grounding wire that is attached to the lid in the left middle area. The connector just pulls free.You should be able to remove the lid after that.
Best of luck,
Vance

I believe some of these relied on a volume pedal for output. Without the pedal the output was very low or not at all. Might check it out. Very nice find!!

That is, or should be, a tone switch. It doesn't make a whole lot of difference on my unit, but it is at least noticeable. Your switch may not be making good contact "corrosion?" in the other two positions. The electronics on mine seems to work great as an antenna and pick up and amplify any interference in the area. I added some makeshift shielding and grounding to help with that. Great instrument though, and strangely addictive to play. You are lucky to source the pluckers as I hear they are hit and miss on availability. I guess only one person makes these?? Congrats on your new instrument!

Also digging the new logo, nice work!

Beautiful! I'm sure it's worth a bit more than what you purchased it for! I have seen others listed in the past that look very much like yours, so I'm not sure what the stamp is about. To me it definitely adds to the cool factor. One similar to it was listed on fleabay as a piano formerly used by the group STYX. Hopefully someone will know the significance of the stamp on your piano and enlighten us. Thanks for sharing!

Just looked back at some of the images I had. The ones I have seen have multiple 6x9? Speakers instead of the two round speakers you have. I think the model number was different as well. I'll look through my pics to see if I can find the model number of the ones I have seen.

Any pictures of this piano?

Since you are using the preamp with an external amplifier and not the Janus amp, you might be feeding a level to hot to your amp which is causing distortion? I am not used to feeding the preamp into other amps so someone who has been doing that would have better suggestions. Maybe describe the amp you are using?
Vance

Maybe the coupling capacitor next to the output jack? Don't know the 54 so just guessing.

Sorry for the late response, things got busy. Tim put it very well. I didn't mean to make it so dramatic sounding. Just means you may have a little extra work involved if you decide to do the bump mod.
Vance

Welcome to the forum Evan! Looks like you scored a pretty nice piano from the pic. Being a 77, you might have the felt on the hammers instead of the pedestals wich would only be somewhat of a concern if you decide to do a bump mod. Other than that, looks great! Look foward to seeing what you cook up on your new grill!

That's crazy!! I have never heard of that happening before. Vintage Vibe actually sold, at one time, a great little video that walked you through setting the offset voltage. I would recommend that if it is still available.

 Just realized that you might not see the power transistors because they are mounted to the heat sink facing outside between the sets of fins. They are usually covered with a shielding that is about 3 1/2" by 1" per pair.

Greetings,
I don't think the question is dumb. Just not sure how to answer other than, "No!", Unless someone else knows more about doing this with your amp and can chime in.
I am not aware of external transistors being used on a fr7710 amp. Maybe the amp tech was confused with the peterson amp that does mount the amp boards in the cabinet?
You state that you have a frx7710 amp. I can't remember if the X identified the unit as wired for 220 or if it was the super satellite amp or other. Regardless, I don't believe it was much different than the fr7710 in basic design.
Maybe if you can post some pics where these transistor sockets or the connector is on the amp board?
In general, I would not try to mess with the amp if it is working well and just serviced. This amp should be able to get very loud, (my neighbors would testify to that). I would be more concerned with the amp board sockets and if their solder joints are solid. This is a problem most of these amps experience.

Well, if you are getting the results you want, that is hard to argue. Glad to hear that it is working better for you!
I would think you could get the same result by placing the existing bump a little further back vs a larger bump. If the playability and sound are how you like it, that is what matters most.

I would look at the placement of the bump on the keys you are having difficulty with. If the mod is not consistent in placement across the keys, you might run into something like you are describing.
Try removing a key that works good and remove a key you have problems with close to it. Compare where the bump is placed to see if one is placed more foward or further back than the other.

Don't see these too often, so thought id, share the one I ran across today. Must have a really nice sound for the asking price!!
http://www.ebay.com/itm/401329341726?ul_noapp=true

Might be a silly suggestion, but do you have a volume pedal hooked up to it? I have read somewhere before that some models have very low output without the pedal connected. Mine was fine without the pedal connected, but might be worth a look if to haven't already.
Best of luck,
Vance

I have enjoyed reading your post, as others, simply waiting for the results. I would imagine they sound very nice.

Here's the key.

Yes, there does appear to be a couple more numbers now that I look at it closer. I have no idea what they are. I can post a pic if you are interested, but they are very faint. Interesting  to know the date information that you figured out, thanks!

Thanks for the heads up on the model identification. It has 11 damperless notes, so, 140. I found a key with a very faint light green stamp looks to be 211166. Havent seen any other number stamps on the keys.

The number towards the right side cheek block is 21113 with the last character after being maybe a 9 or just a wierd backwards p.
The number on the main rail is 21215009 with larger print below of "A 60-2".
I didn't notice any numbers stamped on the keys themselves,  but I  wasn't really looking at the time. I will look again to verify.
The original images are too large to post so I shrunk them, maybe too much...
I'll post again with less shrinking and see if it helps.
Maybe also get a pic of the upper reeds to verify if it is 140 or 140A.

FWIW,
What I believe to be a 140 because of the varistor based tremolo.Unfortunately no serial plackard found on it.

No I don't know what year it was and I was not aware at the time where/how to find the date stamp. I aquired it with a non functioning amp. The mechanics of it played beautifully, so I never looked at the insides much beyond the amp. I'll brows my pictures, but I doubt if I find anything. I would assume it was the same year as yours being so close in serial numbers.

FWIW, I also had a 210 with no aux out. Never took a pic of the date stamp, but got one of the serial plate. Should not have let it go, sounded amazing!

Maybe the cable connecting the preamp to the amp or its connectors is bad. Could also be the preamp  power supply portion of the amp that powers the preamp has issues.

Looks same as the knob on my 700. I measured what looked to be 5/16" for the height and 15/16" diameter.
Don't know what the speaker impedance is on mine but I have a pic of its numbers if it helps. 

I have tried C12N speakers in a 81 suitcase. In my opinion, the highs are amazing and the mids are nice, but it really lacks in the lower bass. I personally liked the original stock speakers better. I have heard the older versions of the C12N are better sounding in the lower frequencies. The  piano has had a fair amount of use now, and I don't really hear any improvement in the lower range from break in. Just my experience, others may have had better success.

I would vote for shielded cable as a good thing if your equipment is properly grounded. And check if your ac outlet is properly grounded with one of those little ac plug testers. If that doesn't work, It could be picked up by the pickup coils in the piano. A Dyno my piano type shielding under the lid might help. Maybe try some aluminum foil wrapped under the lid and run a wire from it to a ground point on the harp to see if there is a difference.

Interesting info, thanks Ben! I had no idea the silver tops had the tape as well.

Yep, what cinnanon said.