Author Topic: Need some back check advice  (Read 1195 times)

Offline theoriginalpol

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Need some back check advice
« on: December 12, 2015, 12:08:30 PM »
Attempting the VV back check mod on a '77, which seems simple enough on its own. However it looks like my hammers rest much higher than the average, because in order to get proper felt contact (full surface) I need to bend the brackets to their absolute max, in which case they lose leverage and don't stop the hammer properly. My first thought is to shim every bracket, which would be kind of a pain and I'd need longer screws, but I'd do it.

Just wanted to crowd source it first, to see if there's a better practice. Like.. should I be more concerned about lowering my hammers? I'd rather not increase my throw distance if I don't have to. But who knows.



Offline pianotuner steveo

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Re: Need some back check advice
« Reply #1 on: December 12, 2015, 01:58:16 PM »
I would ask VV what the recommended angle is. I.e. In a grand piano, the average back check is supposed to be at a 60 degree angle.   Maybe you have them mounted a hair too far away from the hammers?
1960 Wurlitzer model 700 EP
1968 Gibson G101 Combo organ
1975 Rhodes Piano Bass
1979 Wurlitzer 206A EP
1980 Wurlitzer 200A EP
1980 Wurlitzer 270 Butterfly Grand
2000 Yamaha acoustic piano
2004 Hammond XK3
2009 73A Rhodes Mark 7
2009 Korg SV-1 73
....and a few guitars...

Offline theoriginalpol

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Re: Need some back check advice
« Reply #2 on: December 12, 2015, 04:36:35 PM »
I reached out to Quadrapuss personally as well as VV's contact form — haven't heard back :-/

Their video outlining the procedure is great & pretty straightforward — Chris talks about how you'll likely need to bend the brackets some to match the height/distance of your own hammers. Mine just seems to be an extreme of that. You can see in that first photo how I need to get the bracket as close to the hammer as it can go, and bent straight up, to be able to reach right. It's almost like I needed a larger bracket in general.

Thinking more about it, I wonder if changing where they bend up from the screw hole would work? Allowing it more length to pitch up/forward basically? Wish I was at home to test.
« Last Edit: December 12, 2015, 04:38:49 PM by theoriginalpol »

Offline pianotuner steveo

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Re: Need some back check advice
« Reply #3 on: December 12, 2015, 06:36:16 PM »
I would try my idea first.. It's much easier. ( try a few keys) You may only need to move them 1/16"-1/8" closer, then bend to the best angle.
1960 Wurlitzer model 700 EP
1968 Gibson G101 Combo organ
1975 Rhodes Piano Bass
1979 Wurlitzer 206A EP
1980 Wurlitzer 200A EP
1980 Wurlitzer 270 Butterfly Grand
2000 Yamaha acoustic piano
2004 Hammond XK3
2009 73A Rhodes Mark 7
2009 Korg SV-1 73
....and a few guitars...

Offline theoriginalpol

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Re: Need some back check advice
« Reply #4 on: December 13, 2015, 12:34:46 AM »
OK, I think I see what you mean now. Move the bracket even closer to the hammer, putting more pressure onto it?

I just can't seem to find that sweet spot between 'still a little bounce' and 'hammer doesn't come all the way back down' when the bracket's bent at this extreme. Am I being too perfectionist?

VV says to just match the angle of your hammers. Anyone ever try using a contact material besides this strange felt it came with? I cut up a rubber band and layered it over the felt, which seemed to grab a good deal better. Not sure if that'd be viable in the long run though.

Offline pianotuner steveo

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Re: Need some back check advice
« Reply #5 on: December 13, 2015, 11:45:56 AM »
In an acoustic piano, if the back check is too far, the hammer bounces, and if too close, it grabs the hammer too tightly. The principle is the same, and there is a fine line between working correctly, or not working. Putting the rubber band on tells me that slight extra thickness is all you need. Maybe you should try bending at the base, pushing the metal closer to the hammer, then fine adjust with the metal that grabs the felt? Like I said, this is a tricky adjustment in grand pianos especially, but adjusting those back checks to 60 degrees usually is the answer. Of course the angle is different in a Rhodes, but it's the same principle.
1960 Wurlitzer model 700 EP
1968 Gibson G101 Combo organ
1975 Rhodes Piano Bass
1979 Wurlitzer 206A EP
1980 Wurlitzer 200A EP
1980 Wurlitzer 270 Butterfly Grand
2000 Yamaha acoustic piano
2004 Hammond XK3
2009 73A Rhodes Mark 7
2009 Korg SV-1 73
....and a few guitars...

Offline theoriginalpol

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Re: Need some back check advice
« Reply #6 on: December 16, 2015, 01:44:12 PM »
Wanted to post an update here... many days (and Star Wars episodes) later, I finally have everything in a really good functional place, using a combination of all the above advice (thanks again Steveo).

I re-bent every bracket from the screw hole up to have a higher reach, and double-coated the felt contacts. This did indeed turn out to be a lot of extra effort, but IMO was worth it to get a really solid back check going.

To answer my own previous question, I now understand why one might not want to use rubber as a contact material. The exponentially more "grabby" property made it difficult to position the bracket in a way that didn't cause a lot of resistance when pushing the key down again (i.e. the bracket didn't want to let go of the hammer as easily). Again though, in my particular situation the extra finicking was worth it, as the felts alone just weren't working well.

In some ways I wonder if I got a weird version of this kit... the felts seemed like such poor quality, were very hard to peel off without taking a layer of paper with them, there were only 70 of them, and nothing in this kit looked like the parts in Vintage Vibe's video. I just assumed it was their parts/suppliers changing over time though.

Some other notes:
 - I pre-drilled all my holes. In the video he said it wasn't necessary, but my screws didn't look like the self-boring type and I just wanted to play it safe. (EDIT: looking back, this is also recommended in the product description.)
 - I got better action when leaving the part of the bracket that contacts the hammer perfectly straight, as opposed to the slight bend Chris recommends. This probably varies based on your hammer type — mine are '77 all plastic, and have straight shafts.
 - This mod, while simple in concept and worthwhile in result, was much more time consuming than I thought! As always I enjoyed the work — but it left me thankful I don't have an 88  ::)
 - If I had to do it all again, I probably would've taken the shim route. Seems like a simpler, more efficient and sustainable solution to the unique problem I had. But who knows, grass is always greener.


Long story short... my backs are checked! Happy to post final photos for anyone who stumbles upon this in the future.
« Last Edit: December 16, 2015, 01:48:13 PM by theoriginalpol »