Model 120 missing all front rail felts

[theseacowexists]

That's not normal, is it?

[pianotuner steveo]

Yes, it actually is if it's stock. They used a long strip of felt under the white keys at the very front originally on some of the 100 models and on the 700. Some were modified, and the felt strip was removed and people added the individual punchings. If yours has the long felt strip, you probably want to leave it original. They used sticky pieces like a tape on the bottoms of the keys to reduce dip.

[jam88]

Just to add a little to what Steveo said...
The black keys don't have front rail punchings either; they have little felt blocks ("Sharp Stop Felt") on the underside of each sharp key. (See illustration)  Over time, this felt can get pretty compressed from smacking the small area of the flathead screw. I took strips of soft felt and laid them over the screw heads, located by the front rail pins. That felt much better.

On the subject, the action of the 120 was very light and abrupt, like riding a bicycle over a curb. So, rather than trying to weight the keys, I tried putting light foam blocks under the white-keys, over the front rail pins, to provide progressive key resistance. Using these foam blocks, the touchweight of the white keys is now just a little over 50g. Pretty easy to set up--if the weight is too high, just trim a little foam off. If you trim too much off, use another block. 

[pianotuner steveo]

Right, I forgot to mention the black keys. The dip adjustment on those was just a regular wood screw. You raise it to lessen the dip, and lower it to increase it. The felt was so that the key didn't make noise when hitting the screw heads.

The foam idea is neat, but how do you regulate the dip? Do you have standard paper/ cardboard punchings under the foam?

[pianotuner steveo]

Also, it is critical to own a Letoff adjustment tool for these models. Available on eBay. The abruptness can be lessened a bit by setting the Letoff and lubricating. Minute adjustments can make a big change, don't overcompensate.

[pianotuner steveo]

Also, lessening the dip gives you the illusion the action is heavier, and visa versa for increasing the dip. Too much in either direction will cause issues, however.

[theseacowexists]

Interesting! The felt strip is still there, although it feels as hard as a piece of wood. Would I be better off replacing it or getting rid of it and the round felts instead? I actually like the feel of this piano so far, I just don't care for the loud THUNK when playing every key.

[jam88]

The foam idea is neat, but how do you regulate the dip? Do you have standard paper/ cardboard punchings under the foam?

Steveo is right, the first most important tool to have with a 120 is the letoff tool. There is a guy on ebay that has the perfect tool at a good price ;-) This tool can be hard to find, otherwise.

As far as the key dip: the thickness of the compressed foam is negligible. It doesn't really affect the key dip. The keys COULD be shimmed in the traditional manner, but in the 53 years I've owned this piano, none of the white keys were ever shimmed for key dip. If there were a fraction of a millimeter difference from one key to another, I'd never know!

The foam definitely removes the 'hard as a piece of wood' feel from the action. (This isn't as necessary on the black keys, because the player has significantly less mechanical advantage due to the shorter lever arm length of the black keys.)

 

[theseacowexists]

As far as being as 'hard as a piece of wood', I was referring to the felt strip itself! It doesn't have any softness left to it. No cushioning.

[pianotuner steveo]

I would try to find a felt strip to replace the strip in it. Putting individual felts in is not as easy as it seems. You will need paper shims to put under the green felts to adjust the dip. My local dollar tree store sells felt stick on pads like you put under furniture legs. They even have rectangular felts that may be the correct thickness, but you need to buy several strips to get the length. Of course this is just for the white keys.

[theseacowexists]

Thanks Steveo! I'm gonna get a new felt strip for the white keys and new felts for the black keys.

Found a couple other oddities about this one. At least to me - I've never worked on a 100 series Wurli before, so some of this is new to me!

I decided to rebuild the amp, but it appeared to be sealed to the bottom of the piano with some kind of wax. I had to chip all of this wax away to even get to the screws that hold the amp to the case. Is that wax normal?

The amp was easy enough to rebuild, but I noticed that it did not quite match the schematic that's available online. For what it's worth, October 1959 is written on the keys, so that's likely the date of the piano, perhaps they had revised the amp by then. The serial badge says it's a type 1200-1 amp. Anyway, I stuck to replacing exactly what was actually in the amp. What did concern me is that the schematic showed the fuse on the same side of the mains as the transformer and the "death cap" on the opposite side. However, in this amp, both the fuse and cap seem to be on the non-transformer side. If I am going to upgrade this to a grounded three-prong socked (which I would like to), which side should the fuse be on?

[pianotuner steveo]

The fuse should be inline with the hot (black) wire. Remove the "death cap" if it is there ( I didn't see it)  it serves no purpose. The green wire goes to chassis ground. In a modern, 3 wire socket, the black is the smaller prong, the white (neutral)  is the larger prong.  I do not know about the wax, I've never seen that.

[theseacowexists]

I should probably just leave that wax then? It goes from the fuse to the chassis.

[pianotuner steveo]

It probably is best to leave it since it doesn't seem to be hurting anything.

Anyone else ever seen this wax?

[theseacowexists]

It seems to be working fine with the rest of the amp being rebuilt. Everything is new except the tubes, output jacks and the volume pot. There's a low hum in the low third of the volume range, then more of a quieter buzzy hum in the middle third, then the low hum returns on the final third.

[theseacowexists]

Also noticed FWIW: pins 1, 4, and 5 of the octal plug show continuity to each other, even wiring harness is unplugged from the amp. Unhooked the speaker and the speaker showed continuity, even tho it works just fine! The resistance is measuring around 3.2 ohms, that must just be low enough to make the continuity setting on the DMM beep.

[pianotuner steveo]

Any speaker that is working will register continuity. The voice coil is just that- a coil of wire.
If the amp works, don't be too concerned with continuity on the harness.

The hum may be coming from the volume control. A worn control can cause this, but usually it is a loud hum.

[theseacowexists]

I've got a new volume control on order - we'll see if that helps clear things up.

[theseacowexists]

I'm second guessing myself on something else now too. I replaced these two caps with electrolytics - was that correct? They were the only other two polarized caps on the schematic.

[pianotuner steveo]

You do mean the metal cap and the brown one next to it and not the red disc cap, correct?

The metal cap looks like an old electrolytic. Not 100% sure on the brown cap, but you did say that the amp is working, so it is likely correct.

Is that red disc cap the "death cap"? It's hard to tell where it's connected. The disc cap is not polarized.

The death cap that should be removed connected to the AC jack or fuse on one side and chassis ground on the other. Bad news if it shorts out.

[theseacowexists]

Yep, the metal and brown ones.

I still don't think that red disc is the death cap. It's not connected to ground. It's across pins 3 & 6 (I think) of the 6V6. None of the other ceramics are either. The only thing that seems to be in a death cap position is that wax...which I replaced with an equivalent new film cap anyway.

[pianotuner steveo]

I hope that you found a volume control with the power switch attached.. follow the wiring carefully!

Unplug the piano and take a photo before you disconnect any wires from the control.

[theseacowexists]

I did! Only place I could find one that was 1M was on Parts Express. I installed it and it works fine, but it didn't resolve the noise - still a low hum on the first third or so, then the softer buzzing in the middle third, with the hum returning on the final third. Actual signal volume doesn't really increase past the halfway point, but that's fine, since it's pretty dang loud and clear by then.

It's honestly far from the worst noise I've heard. I'm probably just being picky at this point and should just move on to getting the mechanical side of the piano in order (boyfriend says I'm turning into a cork sniffer LOL). Heck, my Pianet hums louder when it sits on the Hammond.

Once I get that taken care of, I am considering replacing the coupling caps per Tropical Fish's suggestion, as they're the only things that haven't been replaced in the amp. The only thing that's confusing is the schematic since they don't give values for any of the ceramic caps, just numbers. Are they in pico or microfarads? My gut is telling me that anything with a decimal (like .02) is micro, and anything without (like 330) is in pico.

[pianotuner steveo]

I think that is correct, but you should get more opinions from guys who are better with electronics.
It's been almost 25 years since I worked on electronics on a daily basis.