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Wurlitzer 4500 pedal rework

Category: Blog Published: 23 January 2019
Written by Matt Roesle Hits: 4652
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When I made my initial repairs of the Wurlitzer I was only able to address some of the problems with the pedals.  The pedals operate with the help of a magnet on the end of each pedal, which closes a reed switch when the pedal is depressed.  Some of the reed switches were broken; at some point, someone had tugged on the wire bundle coming from the pedalboard hard enough to pull the contact out of the end of some of the reed switches.  Replacing those broken switches was easy.  Luckily they still make magnetic reed switches in the exact same size.

Even after those mechanical repairs some pedals still didn't play and others sounded wrong when they did.  The pedalboard is interesting.  It uses two frequency dividers to lower the notes produced by the pedals by two octaves.  But it only has two frequency dividers, so it has to be monophonic -- only one note at a time can be connected to the dividers.  There is a pedal latch circuit that does something clever with a 220 VDC power supply and neon indicator lamps to allow only one note's signal through, even if multiple pedals are pressed simultaneously.

This latch circuit defeated me.  I could see multiple lamps lit, even with no pedals pressed, which I knew was wrong.  But I couldn't figure out what the root problem was.  Maybe all the lamps needed replacement, maybe something else was broken as well.  I didn't want to spend time and money replacing components willy-nilly without understanding what was going on.

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Parents visit

Category: Blog Published: 16 September 2012
Written by Matt Roesle Hits: 14832
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A "blog" with only one entry in it is pretty sad, isn't it?  So let's make it at least one entry per year ...

My parents came over to Europe to visit in September.  I had them with me here in Zurich for three long weekends; they made some other excursions on their own during the week when I had to work.  It was great fun, and the weather even mostly cooperated.  I showed them some of the sights around Zurich, plus we explored some places I haven't been before.

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Grindelwald

Category: Blog Published: 27 March 2011
Written by Matt Roesle Hits: 31274
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In mid-March I spent about a week in the resort town of Grindelwald.  It was a working trip; I didn't get a chance to ski or explore very much.  Still, it was pretty spectacular there.  Our hotel was near the base of the Eiger.  Rather than email a trip report with a bunch of photos to my friends & family, I've finally figured out how to use a photo gallery plugin here.  Very slowly, this is starting to look like a real website!

More, and photos, below the fold.

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