The endless search for the source of the squeals and pops.

[Europanaut]

Well, I've had my 203 for a couple of years. It arrived with a ton of problems. So here's what I've done so far.

New rear wheels.
One speaker repaired.
Tolex repaired.
Replaced some suspect speaker wiring.
Repaired sustain pedal.
Recapped preamp.
Cleaned pcb and potential solder bridges.
Reflowed any suspected cold solder joints.
Replaced the .68 and 200 ohm resistors.
Replaced all transistors (except the 2N3859, which I haven't been able to source yet).
Replaced two reeds.
Carefully cleaned the pickup, and made sure that all reeds have proper clearance.
Tightened pickup connections.

.....and it still squeals and spits like a box of angry pterodactyls.

From what I can tell, the problem is pickup-related. When I unplug the RCA jack from the preamp, all of the unwanted noise is gone. I've done the "lights out" test, and didn't observe any arcing.

Any suggestions as to the next plan of attack?


Thanks.

[pianotuner steveo]

It sounds like either dust/dirt/hair or other debris lying on the reed bar shorting the pickups, or, one or more reeds are crooked in their slots and arcing.

This noise also happens in cold climates when moving a Wurlitzer from a cold location ( like a vehicle) to a warm indoors, but that problem goes away after it warms up enough. Gently clean your Reed bar with compressed air, but keep in mind that compressed air also will temporarily add moisture and it may sound worse before it gets better. You can look at each Reed with a magnifying glass and a flashlight too. I seem to remember a trick of holding white paper under the reeds, then the light under that to make any shorts more noticeable.....

[cinnanon]

Isolate which side of the reedbar the problem is coming from. Unscrew one leg at a time and see what happens. Sometimes a bad connection at the reedbar pickup causes this

[Europanaut]

Thanks.

I've gone through that reed bar so carefully though. I've used air, vacuum, paper, brushes, and even made a tiny metal tool from an automotive feeler gauge to align both sides of the reed precisely and simultaneously.

No results. The noise didn't get better, or worse.

Isolating the reed bar is something that I haven't tried. Interesting. Thanks.

[Europanaut]

Right side pickup is the source of the noise. Left is dead quiet. Out comes the 10x power magnifying glass again.

Update: I did a careful cleanup of the reeds again, followed by compressed air. All seemed quiet, which is odd, because I've done all this before.

I battened it back up, and all was fine. Until I touched the sustain pedal. Lots of mechanical noise from the pedal leaking into the signal patch, AND the squealing started up again.

Getting more interesting, I'd say.

[Europanaut]

I just found something very interesting.

Is there some sort of electrical relationship between the shielding box and the sustain pedal? With the box removed, the sustain pedal doesn't create the squealing noise. When the box is installed, all hell breaks loose when the pedal is pressed. I now have the box mounted as high as possible. The bolts are at the very bottom of the slots.

I've been playing for about ten minutes, and all seems well.

Any hypothesis on this one?

[cinnanon]

The pedal itself should be grounded to the ribbed cable housing. Are you playing barefoot?  Does wearing shoes make a difference?

[Europanaut]

That's interesting. I did notice that the (very slight) background hum changes a TINY bit when I touch the pedal with my finger (I was down there investigating potential ground problems).

The ground wire is present and accounted for. I also ran a second wire (alligator clips) to make sure that the ground wire was doing it's job. No change. I played for a bit last night. With the shield box mounted as high as possible, the noises are much less pronounced. Just occasionally, when using the pedal, I'm getting a bit of a squeal. So I may have identified more symptoms, but an accurate diagnosis and cure is still elusive. I'm wondering if the nylon washers under the pickup-mounting bolts are somehow compromised, and the sustain pedal assembly movement is providing just enough flex to reveal an intermittent issue.

I've been chasing this squeal, off and on, for nearly four years, so I really appreciate all your help. It feels good to make a bit of progress.

[pianotuner steveo]

With the power disconnected, carefully look under the amp pcb and be sure the insulator paper is still there, is not ripped, doesn't have any component leads poking through, and it's not wet. Also carefully look for any solder blobs or anything else that could be shorting out on the board intermittently.

I like to add a layer of electrical tape under that paper.

[Europanaut]

Yep. Done. There's plenty of space under the pcb. It's dry, and intact. Thanks though.

Such a crazy mystery. I've been poking at this for years, and last night was the first sign of progress. With the shielding up high, I get the occasional balloon whistle noise, but NOTHING like what it's been like in the past.

So...we are getting closer to a solution......

[cinnanon]

Well, since you've narrowed it down to the right side of the reedbar, look at the wire leading to it.  Is it frayed anywhere?

[Fred]

Avoid using compressed air at this point. It can be handy in the initial stages of reed bar cleaning (such as when the reed bars are removed from the piano, and followed by complete vacuum cleaning), but at this point, blowing air around in the piano runs the risk of moving debris from one place to another.
Blown air has to go somewhere, and often the problem particles don't quite clear all surfaces of the pickup - a fragment causing a short may just be blown into another area causing another short. Also, in an instrument where even dust can cause all kinds of problems, the compressed air can actually introduce more problem-causing particles from the source itself or from inside the piano.
If you stick to the vacuum, you can at least be sure you're not chasing your tail...

[Europanaut]

Thanks Fred. Understood regarding the compressed air. I've always been reluctant to use it inside instruments. I did apply it sparingly in the Wurli, but relied much more on a simultaneous combination of a gentle brush and a vacuum.

[Electrickey]

I would reflow the entire underneath of the circuit boards just to be safe. Every solder joint on both the amp  and the preamp.

A good solder iron helps. One that is computer controlled.

I did that to my 200a and the pops and storms stopped. This and making sure all grounds are tight and clean touching clean bare metal.

Of course these are imperfect instruments and we tend to judge them by 21st century standards. We expect everything to be zero noise and since we are so used to that we get alarmed when we listen to older technology thinking there's something wrong with them.

They are the best they could be made back then with all their faults. A lot of great music was made with them and with no complains from the listening audience.