The Electric Piano Forum

Repairs, Maintenance & Upgrades => Preamps, Modifications & Upgrades => Topic started by: 5077 on February 10, 2018, 06:06:59 PM

Title: Miracle Mod Issue
Post by: 5077 on February 10, 2018, 06:06:59 PM
Hey EPers,

I am refurbishing my Rhodes Stage 73 Mk I (ca. late '77/early '78) and as part of the process I am installing the Miracle Mod.  I have the parts (thank you Vintage Vibe!), but have run into a problem that I couldn't resolve by looking online. 

I've watched many videos online many times regarding the install of the mod, and I started as instructed: I marked where I thought the bump should go on the high E.  This ended up being about an 1/8" back from the front of the pedestal. (See Pic 1; after looking at the photo, it seems that I could probably put the bump a little bit further back...) (Incidentally, there are no felts on the pedestals as my Rhodes had hammer cam felts, which I removed.) 

Then I went to the low E to do the same, which is when I ran into trouble.  Pretty quickly I saw that I'd have to put the bump right at the edge of the pedestal based on where the hammer was resting.  Once I got in there to do it, I realized the hammer is actually resting on the bump itself when the key is depressed (See Pic 2.) (I was always careful to make sure I was never going into aftertouch throughout this process).  This is problematic, no?  My understanding is that the bump should not be touching (or at most only barely touching) the hammer when the key is depressed.  As you can (hopefully) see in the photo, the cam is not only touching the bump, but it's SITTING on the bump, consequently raising it above the pedestal, as evidenced by the light coming from behind. 

I decided to check another key to see if there was a difference, and it seemed like the hammer cams were getting further and further away from the edge of the pedestal as I went up the keyboard.  After some trial and error, I found that the low Eb--nearly an octave up from the lowest key--was the lowest key I could install the bump and not have it interfere with the hammer cam when the key is depressed.  (See Pic 3; sorry it's not the greatest shot, but it was hard to get at.)

To confirm this discrepancy, you can compare the position of the BACK of the hammer cams to the back of the pedestals between Pics 1 & 2: you should be able to see that the cam and pedestal are flush in Pic 1, but offset by about an inch or so in Pic 2.  (I'm not sure what could cause this issue--a manufacturing quirk??)

So herein lies my problem: do I make my straight edge line between the low Eb and the high E, install the bumps accordingly, and cover all the pedestals with felt?  This will leave the bottom octave with felts but no bumps.  This seems like it will create an escapement issue.  Should I instead install the bumps on the bottom octave anyway, ignoring the interference with the hammer cam?  This seems like it will also cause escapement problems.

I just want to make sure I do it right the first time (and I'm pretty anxious to get back to playing my Rhodes), so any and all feedback/thoughts are appreciated!
Title: Re: Miracle Mod Issue
Post by: 5077 on February 10, 2018, 10:21:11 PM
Well, it's worse than I thought  :(

As you can see in the third photo of my original post, I didn't have a good view of the bump/pedestal on the low end of the keyboard.  I suspected the bump might be impeding the hammer cam even on the Eb, and after checking indeed it was.  I kept moving up the keyboard temporarily gluing bumps and checking as I went and I would now (more confidently than last time!) say that the lowest key pedestal a bump can fit on is key # 24--the second Ab. 

The question remains: is it better to have a bump and felt if the pedestal is sitting on the bump (when the key is fully depressed without aftertouch), OR no bump at all (only felts)?
Title: Re: Miracle Mod Issue
Post by: pnoboy on February 11, 2018, 06:08:29 PM
I think the best bet would be to glue a relatively thin strip of wood on the pedestals that don't stick far enough forward.  Do you have access to a table saw or a router table?  If you do, it should be a pretty quick fix.  The strips wouldn't even have to run all the way down to the keystick.  Just make sure the grain orientation matches that of the pedestals.
Title: Re: Miracle Mod Issue
Post by: Ben Bove on February 13, 2018, 11:45:20 AM
Thanks for being thorough with the pics and description.  The action rail (the aluminum extrusion where all the hammers are screwed into) is slightly misaligned with the key bed.  This can happen on your era of piano, because it didn't have a factory bump, and there was more room for error when assembling and attaching without any noticeable quality control problems.  The hanmmer rolled over the key pedestal just fine in both high and low sections.

The highly involved and correct way to rectify this would be to reposition the action rail and harp supports as they're attached to the key bed.  Basically, rotating the entire left of the action rail back slightly, so your low hammers intersect the key pedestals further back.  However, there's a lot involved with this small adjustment, including redoing the harp's strikeline as its attached to the action rail / supports.

Unless you're down for removing the piano from the case, getting it up on a stand and taking a look at how the aluminum frame is attached to the key bed, and seeing how to adjust it, you may want to take a look at methods like pnoboy is suggesting or other fixes.  The bass section is where the escapement matters most, so you could be running into double-striking in the low section, and definitely a difference in feel across the piano if you did a bump mod as-is.  I wouldn't recommend doing bumps on some and not others - the feel difference would be dramatic.

You might be able to get away with starting on the lowest E at the very edge of the key pedestal, and matching that position all the way up, so your high E is also further back, to match the low E.  Then, when all your hammers match that, you can globally set escapement by raising the harp etc.
Title: Re: Miracle Mod Issue
Post by: 5077 on February 14, 2018, 08:19:14 PM
Thanks pnoboy and Ben Bove for your replies!  Ben, yours was particuarly informative (shame about the QC at the Rhodes factory at the time...).  I see how your suggestion to re-align the action rail would work, but that fix is waaaay above my comfort level. 

I think I'll try pnoboy's suggestion (I do have regular access to many woodworking tools), but I have a few questions:

1. (This one's a concern, really.)  While my knowledge of piano mechanics (and physics!) are admittedly limited, it strikes me that each key is a fulcrum, pivoting on the center rail (or balance rail).  If I add some wood to the pedestal, will that mess with the balance of the key?  I mean, I guess it will be a pretty small piece of wood I'll be attaching, so maybe it won't make a difference??

2.  What type of wood should I use? (Thanks for the tip about the grain orientation!)
Title: Re: Miracle Mod Issue
Post by: pnoboy on February 15, 2018, 12:31:24 PM
You need only a small piece of wood, and by comparison to the weight and moment of inertia of the hammer, the latter of which is multiplied by the square of the action ratio between the key and hammer, you will absolutely not notice any effect from the extra piece of wood.  I think almost any type of wood would be fine, but I'd probably use something harder than pine so that it wouldn't get damaged during future maintenance, such as replacing the pedestal felts. 
Title: Re: Miracle Mod Issue
Post by: 5077 on March 30, 2018, 02:16:12 PM
Just an update for those curious and/or those who come across a similar issue...

I did as pnoboy suggested and cut little pedestal extensions for the keys that needed them.  Luckily, I have a skilled woodworker where I work who has an extensive wood shop with all the tools needed. 

He cut the pieces (Pic 1) which I then attached to the keys (Pic 2), and then proceeded with the miracle mod as usual.  Worked like a charm!

Thanks to everyone who helped out!  :)

Title: Re: Miracle Mod Issue
Post by: Student Rhodes on April 01, 2018, 03:59:45 PM
Very cool.  I love it.
This piano is sure to play better than when it left the factory.