Author Topic: 206 - no sound except 60 cycle hum  (Read 950 times)

Offline Krebstar_3000

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206 - no sound except 60 cycle hum
« on: April 11, 2020, 07:23:43 PM »
Hello all, new guy here. I have used the search function, and have found many helpful posts, but have not been able to find an answer that will help to fix my problem.

I've had my 206 for a long time, but it has never worked. Quarantine has proved to be a wonderful time to catch up on the to-do list backlog! I ordered and installed several parts from Vintage Vibe including the Aux out/ Vibrato mod, in-line fuse, new knobs, new faceplate, new top hinges and hardware, new light jewel, etc. I also got some Protek from ebay.

I've never been very good at soldering, so installing the aux out and vibrato was a major challenge for me, but I did it. I think. I haven't been able to fully test it. I also treated the action centers, eased the keys, and lubed everything that needed lubricating. Quite the undertaking, but the keys react wonderfully now. no sticking anywhere.

Anyway, the problem I am currently trying to solve is that there is no signal. When I turn the piano on, It sounds noisy at first, probably need some deoxit in the volume knob. But then the only sound is a ground buzz, a 60 cycle hum. I get the same thing from the aux out plugged into an amplifier.

From searching here I read about reeds shorting against the pickup. I have used a flashlight and checked each reed several times, but have not found any to be in contact with the pickup bar. What should I try next?

I'm pretty sure that I have correctly re-assembled the piano, and replaced all the grounding wires to where they are supposed to be.

I have the Wurlitzer repair and service manual and have checked the troubleshooting section, but I'm not confident I know what to do with the information it has. If I knew more about electronics I would feel better, but looking at schematics is like looking at hieroglyphics for me.

Troubleshooting page lists the following:

1. No AC power
-I'm good on this one. sorted.

2. Defective transistor- check all transistor voltages (collector-base-emitter)
-I don't know what this means.

3. Shorted filter or open diodes in power supply. - check for low voltage and high voltage and replace shorted filter
-Where is the diode in the power supply? what should its voltage be?

4.Cracked printed circuit
-nah, its good.

5.defective transformer
-the piano turns on, so the transformer is good, right?

6. reed shorted against pickup
- I'm 99% sure I've ruled this out.

7. Input transistor
how do I know if this is shorted or open?

Is there something glaringly obvious that I am missing? Would pictures help?



Offline pianotuner steveo

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Re: 206 - no sound except 60 cycle hum
« Reply #1 on: April 12, 2020, 06:48:53 AM »
Pictures always help, but you may need the help of a local amp guy.

Before you changed or added any parts, did it do the exact same thing?
 If you disconnect  the reed bar from the amp, is there any change? That would tell you if the reed bar is shorted if the hum goes away. Are you aware of the high DC voltage going to the reed bar? Don't mess around with the power on if you don't know what you are touching.

It could be the output transistor(s) , it could be a wire is unplugged (or a broken ground) going to the circuit board, or cold solder joints, or a solder blob laying on the board shorting out parts,etc.

Replacing output transistors is not a recommended DIY job if you don't know about the silica wafer and compound that is needed.
Don't buy random parts to see if that solves the problem.

Detailed pictures of the amp board may help a lot.
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 Krebstar_3000

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Re: 206 - no sound except 60 cycle hum
« Reply #2 on: April 12, 2020, 08:11:10 PM »
Thank you for your response and insight.

I am aware of the DC current, but I appreciate the prudent warning.

The fuse was blown and the AC wires were cut when I got it. This is the first time it has been turned on in a long time.

I don't know why I didn't think of unplugging the reed bar from the amp. Basic troubleshooting right there. Yes, when unplugged, the hum goes away. So, that being the case, please forgive me for not doing my due diligence before asking for help.

I have once again visually checked for reeds shorting against the pickup bar. The tolerances are so tight it can be difficult to tell. I have used a flashlight to see, and each one appears to be correct. I assume if a reed were making contact, there would be a mechanical noise to go along with it, right? metal vibrating against metal? I haven't found evidence of that.

The ground wires are intact, and I think I have them installed in the correct places. Here are pics of the ground wires and the circuit board. Please feel free to point out what I have done wrong, and thank you for taking the time to assist me.




Offline pianotuner steveo

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Re: 206 - no sound except 60 cycle hum
« Reply #3 on: April 12, 2020, 09:03:33 PM »
There are some not so great looking solder connections on the board, but that may not be it.
Have you checked the reed bar with an ohm meter for shorts? Place one lead on the + and the other on the - of the reed bar. (Power off) I can't see where the + wire is connected.
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 pianotuner steveo

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Re: 206 - no sound except 60 cycle hum
« Reply #4 on: April 14, 2020, 04:23:14 PM »
I meant to say to disconnect the reed bar from the amp too when checking to see if the bar is shorted.
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 Krebstar_3000

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Re: 206 - no sound except 60 cycle hum
« Reply #5 on: April 18, 2020, 08:08:38 PM »
You know, there may not be current running through the reed bar after all. I just assumed there was and was careful not to electrocute myself. But like you said, I can't see where the + wire is connected either? Where should it be? I have looked through the service manual and stared at the amp board, and looked at many pictures online, but I'm lost.

Which part of the reed bar is + and which is - ? I have a meter and have tried to find what you are asking about, but have only found out how little I know.

Thanks for being patient and pointing out what might be obvious to the more initiated. There are techs where I live, but transporting this thing is not easy, and at this point I would really like to understand more and try to get it going myself.

Offline pianotuner steveo

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Re: 206 - no sound except 60 cycle hum
« Reply #6 on: April 18, 2020, 09:56:11 PM »
As I have said many times, I am more of a piano tech than an electronics tech, there may be others here that can answer those questions easier. My 206 isn't easily accessible at the moment, and mine is a 206A, is yours an A or just a 206? I think yours is a non"A".

The voltage at the reed bar is DC, not AC, it can still hurt if you get a shock, but it's not enough to electrocute you.
Do you know how to input a different audio source into the amp if you unplug the reed bar? If you do, that will tell you if the amp works or not. But you need to verify that there is no DC voltage at that RCA jack first.

I believe the shiny aluminum part of the reed bar is + and the thicker metal is - , but do not quote me on that,it's been a long time since I've worked on a model without a preamp board. I only have the "A" models with the preamp boards here. (200A and 206A)


With the power off, you can disconnect the reed bar RCA plug, then check the + and - on that plug to see if they are shorted- your Ohm meter will read 000 if the bar is shorted. Or just 0 if analog.
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 Krebstar_3000

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Re: 206 - no sound except 60 cycle hum
« Reply #7 on: April 18, 2020, 10:30:25 PM »
Wonderful info, thanks. Yes, it's a 206 (non-A). I believe it is from 1972.

Offline pianotuner steveo

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Re: 206 - no sound except 60 cycle hum
« Reply #8 on: April 19, 2020, 01:29:49 PM »
Ok, I just looked at your pictures again,and this time I saw where the + wire connects. It appears to be connected in the right spot, but something seems odd with the wire on the right side of the reed bar. It may be just an odd angle, but it almost looks like the + wire is touching ground where the wire splits. Also, does anyone on here remember if those resistors are supposed to be there?
« Last Edit: April 19, 2020, 01:33:50 PM by pianotuner steveo »
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 Krebstar_3000

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Re: 206 - no sound except 60 cycle hum
« Reply #9 on: April 29, 2020, 06:43:50 PM »
It's been a few days, so I though I would report back in. Turns out the short was of my own doing (big surprise there). in the 4th pic from the top (above) the ground wire was connected to the reed bar. I moved it to the front, to the screw that holds the shield in place, and voila! The piano signal came through the amp! There is still a buzz coming through, that goes away when pickup is unplugged from amp. Currently trying to figure that one out.

Offline pianotuner steveo

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Re: 206 - no sound except 60 cycle hum
« Reply #10 on: April 30, 2020, 09:12:20 PM »
Lol, yeah it's obvious now.. did you use a 3 prong cord when you added the AC wire? If the ground wire is properly connected there, then the hum should be reduced more. If someone else added the AC cord, double check to see if they used the ground wire.
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 cinnanon

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Re: 206 - no sound except 60 cycle hum
« Reply #11 on: May 01, 2020, 05:16:40 AM »
If the buzz goes away when the pickups are unplugged, turn your lights off nearby to see if it goes away. If not, check the grounding further on the reedbar.

Offline pianotuner steveo

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Re: 206 - no sound except 60 cycle hum
« Reply #12 on: May 01, 2020, 06:00:00 AM »
That ground wire that was the culprit should go to the ground side of the reed bar, that may help too.
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...