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Got a friend's Wurlitzer 200A electric piano that I'm working on. It's a little on the buzzy side. Not terrible, really not that much worse than a single coil guitar, but enough to be annoying. It looks like it uses a long bar with 150V on it that grounded reeds vibrate over as a capacitive pickup. If I ground out the 150V bar (via a cap, of course) the buzz goes away, so it appears it's the bar picking it up. I don’t know if I can rule out the 150volt supply but a) it’s isolated from the pickup by a 22k resistor so it seems like it would still inject noise if when the pickup was shorted out if it was the problem b) I beefed up the filtering significantly and it didn’t change anything. So, long story short…anyone know if it's normal for these things to pick up a lot of buzz?
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When I rebuilt mine a few years ago, I found that the there were so many redundant grounds that it was one ground loop after another. Also, watch where the 120v ac line that runs to the power switch is located. I think that if you move it around away from the audio cables it will help some too.
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Thanks Bill. Yeah, I noticed that about the grounds and already took care of it. This appears to be noise that the pickup is picking up, since I can kill it by grounding out the pickup with a cap. I now see that there originally was a shield plate that goes in between the most of the electronics and the pickup bar. This one is missing it. That could have a lot to do with it. I'm going to try making something for it and see if it helps.Comment
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There should be a large aluminium shield that covers the entire reed/pickup assembly. It is L-shaped and is held in position with a bunch of I think 6-32 screws. If you need to see one I can photo mine, or send a scan of the repair manual page.Comment
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Thanks again, Bill. I found some pictures online. There are even a few for sale, but for ridiculous amounts of money. I think I can make something without too much fuss.Originally posted by 52 Bill View PostComment
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