Author Topic: Cembalet N Squealing Noise  (Read 188 times)

Offline theseacowexists

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Cembalet N Squealing Noise
« on: September 06, 2019, 11:16:53 PM »
My Cembalet N has been in storage since April, and when I pulled it out earlier this week, it was noisy as all heck. Specifically a squealing/oscillating sound, accompanied by some random clicks and pops. It's loud enough to be noticeable while playing. I had noticed the squealing noise a couple times before it went into storage, but it was never anywhere near as loud and constant as it is now. Any idea what might cause this? All of the components on the board are new, except for the transistors, rectifier, and Beyer transformer. Also, this happens in any room in the house and with any amp, so it's unlikely that it's interference.

Offline OZDOC

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Re: Cembalet N Squealing Noise
« Reply #1 on: September 08, 2019, 12:09:41 AM »
The first thing that comes to mind is a faulty capacitor - but you say they've all been changed.
So, possibly some dust bridging a reed/pickup gap? Run a slip of 80gsm bond paper through the gap between reed and pickup.

Offline theseacowexists

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Re: Cembalet N Squealing Noise
« Reply #2 on: September 08, 2019, 10:50:49 AM »
You're right - it was something in the harp. I pulled back all of the dampers, and the squealing noise was much quieter, and the static and clicking was gone. Just to be sure, I disconnected the harp from the preamp, and sure enough all the noise was gone. Now, I took your advice and cleaned each gap, but then I realized that the place this had been stored for the past five months was my parents basement (long story), which is pretty damp. So I took the hair dryer to the harp for a few minutes, cleaned the gaps again, replaced the dampers, and voila, no more squealing. Only the tiniest of clicks here and there. Thanks for pointing me in the right direction!

I can't help but wonder though if those felt dampers are to blame for the noise. As I had said in another thread, every key would make an audible click when activated until I grounded the copper damper holders. The felts have little stray fuzzies on them (they're felt, after all), and I can imagine that it wouldn't take too much for some of those fuzzies to come loose and wreak some sonic havoc on the pickup. Perhaps it's time to try making some dampers out of foam instead...

Offline OZDOC

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Re: Cembalet N Squealing Noise
« Reply #3 on: September 08, 2019, 06:21:31 PM »
I think you're on to something about the felt dampers. The originals were urethane foam I think.
It is quite possible that the felt is inducing a static charge on the reed.
The Pianet suffered from similar problems when the original leather and urethane pads were substituted for solid silicone pads.

Offline theseacowexists

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Re: Cembalet N Squealing Noise
« Reply #4 on: September 10, 2019, 07:17:21 AM »
I might try out some foam and see how that works out. How is your Cemablet coming along?

Offline OZDOC

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Re: Cembalet N Squealing Noise
« Reply #5 on: September 10, 2019, 07:44:56 PM »
My Cembalet restoration got put on hold while Alan and I completed the book on vintage keyboards we were writing - see Classic Keys, Lenhoff & Robertson on Amazon Books.
There are a few photos of my earliest Cembalet in that. But, with your experience in mind I think I'll set aside the felt dampers that I was going to fit to it, and find a suitable foam extrusion. There is no doubt that the felt has the ability to retain charge - which is always a point of concern with capacitive pick-up systems.