Wurlitzer rattle

[mooneh]

Hi all,

I'm hoping for a reality check from other Wurlitzer owners.

I have a Wurlitzer 200 that I want to sell. When I unplug it there's little mechanical rattle/resonance around the middle octave. It's not a single note, more like a narrow midrange band. It disappears when the sustain pedal is pressed and only noticeable when I hold down a key a little longer.

A few observations from troubleshooting:
   •   The noise is purely mechanical (present with the piano powered off).
   •   It becomes progressively quieter as I remove more of the rear damper springs, and comes back as they're reinstalled.
   •   It changes depending on how the piano is supported (legs vs stand, slight twisting).
   •   Light pressure on the right-hand side of the damper rail makes it disappear.
   •   Thin fiber/cardboard shims installed between the damper rail and its metal support on the right side. They initially changed the resonance, but after some playing the noise returned.
   •   Reed bar shields are installed.

For context: my parents (both 70+) can't hear the rattle at all and think I'm imagining things. I tried to record it with my phone but the noise from the phone was higher. I can't hear the noise when the amp is on. 

So the simple question:
Is this kind of unplugged mechanical resonance normal for a Wurlitzer 200/200A, or am I overthinking it? When I had it on a keyboard stand without the legs it was worse and I could also hear it with the amp turned on.

Any insight appreciated. Thanks.

I have had bigger rattling noise problem before, but then it's been the case that's been loose, but I've checked everything now, almost completely dissembled everything and start to think this is normal.

[velo-hobo]

Welcome to the ol' forum!

Hard to say what the problem is exactly without sound/video clips or in-person inspection but it should be possible to hunt this down, considering the conditional aspects you've already identified.

• Does the noise happen even if the sustain pedal is not connected to the piano at all?

• Is there any slack in your sustain mechanism when the pedal is connect but it is not engaged/under tension? I wonder if there could be rattle in the mechanical linkage between the upper end of the pedal cable and the damper rail lift arm.

• Check the tightness of the bolt/nut that attaches the sustain connecting rod to the damper rail lift arm. There should be felt washers on either side of the lift arm that act as thrust bearings for the bolted connection, as well as metal washers outboard of the felt washers.
• Check the metal cap that bears against the big return spring - ensure it is not loose/rattling and that the spring is seated inside the lip of the metal cap.
• Also, check that the wooden block underneath the spring is screwed down tight against the floor of the case.

Don't touch the sustain adjusting nut or cable adjustment inside the sustain pedal right away! Try to find the problem and positively identify it before making any changes to the sustain mechanism.

If the rattle does not seem to be coming from the sustain linkage, the fact that removing the "damper return springs" is another clue - by which I think you must mean the long-neck screws sticking up out of the damper connecting rods? The ones with the rubber grommets that push into metal clips at the rear of the damper levers.

It's possible some of the damper levers themselves are rattling around, perhaps because the damper flange screws are not tight, or it could be something else in the action. For example, those rubber grommets can become quite hard over time, which could increase the noise level of any screws rattling around inside the grommets.

Troubleshooting like this can require patience, and sometimes a few attempts at hunting down the problem. But it is very satisfying to figure it out, even more so when the solution presents itself as being quite simple and quick.

(Yes, Wurlitzers do make mechanical noises and can have odd resonances, but in my experience these aren't always an issue for the player depending on the use context. If it is distracting or audible to players/listeners/recording devices then for sure attempts should be made to mitigate it. Recently I put some reed bar shields into a 720 and found it created a high-pitched resonance. I had to fuss with the tightness of the screws holding down the shields a bit to get it to go away, among other poking and prodding. But hey, I'd rather hunt down weird mechanical anomalies than rework a SMD PCB)

[mooneh]

Thanks a lot for the detailed reply, really appreciated.

Yes, the noise is present even if the sustain pedal is completely disconnected from the piano.

Regarding the "damper return springs": yes, I meant the long-neck screws with rubber grommets that push into the metal clips at the rear of the damper levers. What's interesting is that the noise gets progressively quieter as I remove more of those, and returns as they're reinstalled. My hand pressed on those doesn't make any difference but pressure on top of those wood dampers they are connected to reduces or eliminates the rattle.

At this point I probably wouldn't notice it anymore, since I can't hear it once the piano is powered on. Earlier, when it was sitting on a keyboard stand instead of the legs, it was much worse, and I could actually hear it even with the volume turned up.

Since you mention that these instruments do produce some mechanical noise, I'm starting to think this might be normal. My only concern is whether it could become more noticeable again once everything is fully reassembled with the lid back on.

[velo-hobo]

No problem, glad to offer my thoughts.

Have you checked that the damper flange screws are all tight? If any of those are loose, they could rattle against the damper rail, and it would explain how you can damp the noise by pressing down on the dampers. Make sure the tongue-and-groove features on the mating surfaces are aligned and use care when tightening these screws (and other wood screws that hold the action parts together) as the flanges can split if handled roughly. Fixing them is fairly easy - wood glue and a small clamp - but best to avoid, of course.

If it continues to be a bother, some audio and/or video would be helpful. It's hard to say, but it is notable perhaps an encouraging sign that you can make the sound go away by pressing on the damper levers.