Author Topic: Need Help Diagnosing a 200A  (Read 240 times)

Offline takumisrightfoot

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Need Help Diagnosing a 200A
« on: August 11, 2020, 12:11:01 PM »
Hi all,

By the sheer grace of God, I was given a Wurlitzer 200A yesterday. According to the kind gentleman who had it before me, he found it on the curb and played it for a while before a power surge during a thunderstorm rendered the instrument inoperable. I plan to attempt a repair myself, but wanted to consult y'all for some guidance on troubleshooting before getting my hands dirty. I'm pretty handy with a soldering iron, but my knowledge of circuitry is rudimentary at best. Any help or pointers that y'all could give would be greatly appreciated. Cheers!

-Ethan

Offline sean

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Re: Need Help Diagnosing a 200A
« Reply #1 on: August 11, 2020, 03:06:02 PM »

Ethan,

Rudimentary knowledge will get you pretty far if you have patience and common sense.  You should study the schematic in the service manual (or find a friend to show you how to read the schematic), and identify the parts on the circuit boards.

This is the 200A manual from Vintage Vibe's manuals page (https://www.vintagevibe.com/pages/service-manuals):
https://cdn.shopify.com/s/files/1/0666/2821/files/Wurlitzer_200_and_200A_Service_Manual.pdf?8872610067384662061

Note that the manual has many different piano versions all crammed into one document, so you have to keep your eyes peeled for the "200A" content.  Keep hitting page down, and don't lose hope.  Eventually you will get to page 62...   Then you have to decide if the schematic on page 66 matches your piano, and then wonder why there is no similar schematic for the early production models like the table of contents on page 62 leads you to expect. 


Well, you will realize that there is nothing to do until you get your hands dirty.  Check the slow-blow fuse on the AC input, it may look fine, but test for continuity with your multimeter.(*1)  Look for smoked or burnt sections on the circuit board.  If you are lucky enough to find a burnt spot, that is a pretty obvious indicator that the components in that area need to be replaced.   You can test the rectifier diodes, but it is easy enough to just swap them out with new ones.  Test all the voltages around the voltage regulator (IC-1).  You should also expect to replace each and every one of the large electrolytic capacitors.  Remove the "death cap" - the .01uF capacitor right next to the neon bulb on the schematic.

Sean


(*1) Do not admit that you don't own a multimeter.  How embarrassing.  What have you been doing with your life?  Everyone should have a multimeter, and they are practically free:  six bucks will get you one that works very well for low-voltage work.  See  https://www.harborfreight.com/7-Function-Digital-Multimeter-63759.html
« Last Edit: August 11, 2020, 03:11:17 PM by sean »

Offline takumisrightfoot

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Re: Need Help Diagnosing a 200A
« Reply #2 on: August 11, 2020, 05:52:50 PM »
Hi Sean,

First of all, thank you for the wealth of information that you've provided me with. As a side note, I picked up the multimeter you suggested... you know, to replace the one I lost ;)

Just for some clarification on the points you specified, I have a few questions:

To get these replacement parts, such as the electrolytic converters and rectifier diodes, would it be best to just get one of the Vintage Vibe Wurli Amp Repair kits ($42) or source the parts individually? Should I replace the "death cap" with a piece of wire or just take it out? Lastly, when testing voltages (with everything plugged in) are there any precautions I should take to avoid electrocution/accidentally frying something?

Again, thank you for the help!

-Ethan

Offline pianotuner steveo

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Re: Need Help Diagnosing a 200A
« Reply #3 on: August 11, 2020, 06:13:05 PM »
No! Do not replace the cap with wire! That is bad. If the cap shorts out, that's virtually the same thing as putting in a piece of wire. Just remove it. It is likely far easier in the long run to buy the kit from VV. Make sure you install electrolytic capacitors according to the correct polarity.

Someone was throwing out a 200A? Wow. I found a 120 waiting for trash pickup once, but never a 200A!

Yes, I rescued the 120. I'm kicking myself for not keeping it though.
1960 Wurlitzer model 700 EP
1968 Gibson G101 Combo organ
1975 Rhodes Piano Bass
1979 Wurlitzer 206A EP
1980 Wurlitzer 270 Butterfly Grand
2004 Hammond XK3
2009 73A Rhodes Mark 7
2009 Korg SV-1 73
2017 Yamaha P255
2020 Kawai CA99
....and a few guitars...

Offline sean

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Re: Need Help Diagnosing a 200A
« Reply #4 on: August 12, 2020, 01:13:27 AM »

Ethan,

I cannot stop giggling about this.  What part of "remove the death cap" would lead one to believe that I meant "replace the death cap with a piece of wire"?  I must therefore assume you were joking.  Well played.   And wait a second, that cap doesn't qualify as a death cap, because it doesn't have one leg touching ground.  Right?  It could fail to a short circuit, and that would blow the fuse, but not expose the chassis to the AC mains.   Hmmm... does that cap protect the neon bulb from kickback when power is turned off? I dunno.  Maybe I should not have recommended removing it.

You should absolutely positively buy the vintage vibe kit.  They have selected capacitors that meet the capacitance value, voltage rating, temperature rating, ESR, physical size, and sexual orientation (axial or radial leads).  What's it cost?  14 capacitors for 42 dollars?  Three bucks a component.  That's fair and resonable.

If you were experienced in selecting electrical components, you would not have asked the question.  It takes a long time to shop online for components (there are a TON of options, and a TON of specs to verify).  You can theoretically save a small bit of money buying all the components from Digikey or Mouser, but you have to get lucky and make all of the component selections correctly - so that you don't have to re-order any items that you got wrong (and pay for shipping again).  But whenever I am searching for components, I always stumble across an amusing option:  see https://www.digikey.com/product-detail/en/avx-corporation/SXP37C334KAA/478-6179-ND/2346149 (Prices like diamonds).  I see that the VV kit does not include the rectifier diodes.  Let's hope they are fine, and the lightning just blew the fuse.  Let's also hope that the transformer isn't damaged.

You also bring up a very good point - shame on me for not suggesting this first:  Yes, you should be careful while testing with the power turned on!  My advice is, uhm DON'T TOUCH ANYTHING!  There is a high voltage section coming off the transformer (blue wire).   See the schematic area just below the transformer.  The little ladder of capacitors and high-value resistors smooth out the high voltage and feed the high voltage to the reed bar (black wire).  Look closely at the circuitry in your piano and locate these components, and do not touch them. 

Now look at the upper left corner of the schematic where the connection labeled "18" comes from the little ladder and goes through the 1Meg resistor, then makes a turn through the 22K resistor over to the screw that connects to the reed bar.  Do not touch anything to the left of the .022uF capacitor.  These components are on the little circuit board mounted up on the reed bar.  Find them, and do not touch them.  Oh yeah, don't touch the reed bar either.

Also, while you are poking around with the probes from the multimeter, be careful.  It is very easy to slip and touch the wrong thing, because you set the probes in the desired position and then you turn your head to look at the meter readout.  Put the meter close, and on a secure surface, and don't tug on the probe wires or the meter falls over.

Oh yeah, and before you get into this, watch these videos:
1.  https://www.youtube.com/watch?v=2Fmpepn5e0c
2.  https://www.youtube.com/watch?v=tQtgS7C03ck
3.  https://www.youtube.com/watch?v=BLLme1Temmk  Oh my, they look so young.  It's a wurly, but not a 200A!
4.  https://www.youtube.com/watch?v=aI7Y5Whjfe8  not any wurly, but....

Sean

Whoa!   VV has a much clearer 200A schematic as the install directions for their rebuild and hiss-killer kits. 
See https://cdn.shopify.com/s/files/1/0666/2821/files/Wurlitzer_200A_-_Rebuild_Kit.jpg
and https://cdn.shopify.com/s/files/1/0666/2821/files/200A_Hiss_Killer.jpg
« Last Edit: August 12, 2020, 01:39:32 AM by sean »