Author Topic: Repairs on a Wurlitzer 300  (Read 535 times)

Offline Figno

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Repairs on a Wurlitzer 300
« on: May 03, 2018, 05:02:36 AM »
Hello group,

I'm new here, so far I am impressed with the kindness on this forum. I wished facebook was like this :-)

I am working on a 300 for a local studio. This one makes a lot of noise (hissing and popping) like a leaking capacitor or broken resistor. But so far all the resistors and caps seem fine. When I disconnect the volume pot the noise dissapears. Introducing audio at the volume pot return line results in a clean signal. So the problem is in the pre-amp.
I noticed a faily new transistor at Tr2, a BC169B. I suspect someone has serviced this 300 before and replaced the transistor with something that seemed compatible but is not. So the hunt for the right transistor has started, but: I can't find any info on the 300. No part lists, no schematics. It looks fairly like a 206 schematic but its not exactly the same.

Does any of you have a schematic or partlist? Any ideas which transistors to use? I am tempted to 2n2926 or 2n5089 (as in 200 and 206).

Cheers and keep up the good work.

Offline pianotuner steveo

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Re: Repairs on a Wurlitzer 300
« Reply #1 on: May 03, 2018, 07:27:08 PM »
Hissing and popping usually is caused by dust/dirt/solder blobs or other foreign matter laying on the reeds. It also can happen from condensation when moving a Wurlitzer from a cold environment to a warm one.

Inspect and clean the reeds before messing with components. A brush and an air compressor will help, but the compressor can cause temporary condensation as well.
The reed bar is essentially the preamp.
« Last Edit: May 03, 2018, 07:28:58 PM by pianotuner steveo »
1960 Wurlitzer model 700 EP
1968 Gibson G101 Combo organ
1975 Rhodes Piano Bass
1979 Wurlitzer 206A EP
1980 Wurlitzer 200A EP
1980 Wurlitzer 270 Butterfly Grand
2000 Yamaha acoustic piano
2004 Hammond XK3
2009 73A Rhodes Mark 7
2009 Korg SV-1 73
....and a few guitars...

Offline Figno

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Re: Repairs on a Wurlitzer 300
« Reply #2 on: May 04, 2018, 03:26:03 AM »
Hello Steveo,

Thank you for your rrply. The reeds were my suspect too but when I disconnect the reedcable the hissing and popping stays. I will do some more measurements soon with my scope to see where the noise is introduced.

Offline pianotuner steveo

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Re: Repairs on a Wurlitzer 300
« Reply #3 on: May 04, 2018, 06:34:35 AM »
I thought that you said when you bypassed the reeds and injected a different signal, the audio was clean. I've never actually seen a 300 in person-do they have the little preamp board mounted in the middle of the reed bar like the 200A? If so, check that board for cracked traces, etc.

1960 Wurlitzer model 700 EP
1968 Gibson G101 Combo organ
1975 Rhodes Piano Bass
1979 Wurlitzer 206A EP
1980 Wurlitzer 200A EP
1980 Wurlitzer 270 Butterfly Grand
2000 Yamaha acoustic piano
2004 Hammond XK3
2009 73A Rhodes Mark 7
2009 Korg SV-1 73
....and a few guitars...

Offline Tim Hodges

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Re: Repairs on a Wurlitzer 300
« Reply #4 on: May 04, 2018, 08:09:32 AM »
It uses a 200 model amp, so no separate pre-amp board.
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Offline DocWurly

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Re: Repairs on a Wurlitzer 300
« Reply #5 on: May 04, 2018, 08:49:50 AM »
Does a 300 have the same electronics as a 201?  If so, that would increase your potential user database a tad.

Offline Tim Hodges

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Re: Repairs on a Wurlitzer 300
« Reply #6 on: May 04, 2018, 09:53:15 AM »
Not the best image but this shows a 300 amp:

http://www.kerschhofer.net/wurlitzer-replacement-amp/original-board.png

Found this comment by Jenzz:

Quote
The innards and circuit are the same as the EP201, a EU-Version of the original 200. The amp is close to the 200 schematic, but has some additional things like a trimpot for adjusting tremolo Speed and two trimmers for power amp bias.

Olivier's picture is intriguing, you can see some of the amp but I love how they've just taken a standard pedal and mounted it to the case:

http://olivier-grall.yusynth.net/instruments/Pianos/WURLITZER/wurli%20300%20rear.jpg
« Last Edit: May 04, 2018, 09:59:59 AM by Tim Hodges »
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Offline Jenzz

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Re: Repairs on a Wurlitzer 300
« Reply #7 on: May 05, 2018, 02:40:34 PM »
Hi all :-)

Since i have a 201 in for service (the 300 uses the same PCB), i will take some pics of the PCB tomorrow...

....stay tuned ...

Jenzz