Author Topic: Noise in the amplifier.  (Read 755 times)

Offline Argi

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Noise in the amplifier.
« on: June 02, 2019, 10:32:16 AM »
Hi from Spain.
  This is my first message in this forum. I need some help. Thank you!
Well, I'll tell you: I bought a 200 wurlitzer and I'm working on it to have a great piano.
I have already regulated the action and I have also restored the wooden base of the piano. The keys are also clean and regulated and the reeds are in their tone.
The problem is the amplifier, there is a lot of noise and interference. Also if I touch the amplifier with a wood, it makes noise.
I have verified that the noise comes from the amplifier not from the bar reed.
What I would like to know is that changing all the components of the amplifier will remove the noise. This is my question.
I have little knowledge of electronics, I can solder and measure resistors, diodes ..... but little else.
I await your answers and greetings.

Offline beginnersluke

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Re: Noise in the amplifier.
« Reply #1 on: June 03, 2019, 08:50:45 AM »
Hi Argi,

I'd say two things. It's an old amplifier, meaning old components and an old design, so I don't think anyone can really say that it will be noise free if you replace all of the components.

Here's what I would say:

1. In any old piece of electronics, it's a good idea to replace the electrolytic capacitors (the ones that look like metal cans). This often helps on a number of fronts (though safety and reliability are probably #1).
2. You can also replace other components like resistors in the signal path, other capacitors, transistors (especially output).
3. The 200 does not have reed bar shield; it is recommended that you install them to limit noise, especially hum.
4. Many people replace the amplifier with a modern design with new components. (There are three options that I know of, incl Vintage Vibe, Retrolinear, and Borish electronics.)

If you want to rework your amp, I'd start with the electrolytics and the hum shields and see how much that helps.

If you have a service manual, you can figure out the values and order from an electronics warehouse. (You can also just read them off the old components.) You can also get rebuild kits and transistors from Vintage Vibe. (You'd probably need them for the output transformers.)

Good luck!

(PS Electrolytic capacitors have a + side and a - side, unlike resistors. Your PCB should have a marking on where the + lead goes.)

Offline Argi

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Re: Noise in the amplifier.
« Reply #2 on: June 04, 2019, 12:13:37 AM »
Hi, beginnersluke.
 The reed bar shield already I have it and I have verified that the noise comes from the amplifier.
I will start to change the electrolytic capacitors.
Thanks for your answer.
Greetings.

Offline Electrickey

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Re: Noise in the amplifier.
« Reply #3 on: June 13, 2019, 07:35:59 AM »
This has come up before.

I would try getting a good heat adjustable solder station and reflow the solder spots on the amp and preamp if you have basic soldering skills and see if that fixes the noise problem before assuming there's something wrong with the components. Unless it's apparent that there are  bad parts, sometimes reheating the solder holding the components to the circuit boards will reconnect anything that has become intermittent over the decades.

I did this to my 200A and no more thunderstorms, or static.

Changing components in a vintage amp, note that the tone will change as well.
Just because a part has drifted from spec, use your ears. If the piano sounds good then why change the components off the bat.

Isn't the sound more important than if the caps and resistors are at tolerance.

Of course if there is any danger the parts will burn and cause a fire, then by all means change it.

But a vintage sound is usually the vintage parts having settled to a particular state that gives the instrument the desired character.

Make sure the ground lugs around the inside of the piano are clean and tight.

If your solder skills are not up to it, have someone who is good at it do the work. You don't want to mess anything up turning your vintage Wurli into a guinea pig experiment.

Respect the instrument.

« Last Edit: June 13, 2019, 07:38:21 AM by Electrickey »

Offline Argi

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Re: Noise in the amplifier.
« Reply #4 on: June 15, 2019, 01:07:02 AM »
Hi from Spain.
Thanks for your answer!
  My soldering iron and my welding skills are basic so I will take the amplifier to a technician to check the welds.
I've worked a lot on this piano and I have to try to make the noise disappear, it's the most important thing!
I will also check the ground points.
Thanks for everything.
« Last Edit: June 15, 2019, 01:08:33 AM by Argi »

Offline Electrickey

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Re: Noise in the amplifier.
« Reply #5 on: June 15, 2019, 06:42:26 AM »
Hi from Spain.
Thanks for your answer!
  My soldering iron and my welding skills are basic so I will take the amplifier to a technician to check the welds.
I've worked a lot on this piano and I have to try to make the noise disappear, it's the most important thing!
I will also check the ground points.
Thanks for everything.

You may want to impress upon your technician that you would like each solder joint reflowed. It would be best that you do not assume the technician will think to do this. It will take some time to do each and every weld point.

What we are explaining to you is a repair procedure that we've discovered as owners/service people on these instruments and may not be part of your technician's habits.

If your technician understands the complete reflow procedure we've described on this instrument, then no problem.

Before you leave your instrument at the technician's shop, you would want to know that they have repaired a Wurlitzer electric piano before.

If not, try and find a technician, or another musician-hobbyist like yourself with more experience with a solder station and on complex circuit boards.

• It is important that when reflowing each weld, that the solder does not connect outside of each weld's circuit, not touching other welds, that should remain separate from the other and that the solder iron does not burn the board or overheat the components. This is why a proper solder station unit is needed to quickly apply the right amount of heat in the quickest amount of time and that one's solder skills are good enough to do this.

• The 200A's circuit boards are now 50 years. They may need a better modern solder station.

I used one of these on my 200A's amp and preamp and purchased it just for reflowing the Wurli's electronics. It measures the amount of heat needed at the weld and applies just enough heat to melt and flow the solder.

This is not the type of station using a manual heat control knob or button.



The Jovy iSolder 40 is a copy (somewhat) of the Metcal smart solder, but made in China. 

Metcal makes many models and they started in Silicon Valley making equipment for the military. They are pricey and come from different parts of the globe.

See video below for the Metcal.

https://vimeo.com/200519529



Suffice it to say my Jovy lasted just a little longer (about 2 years) after reflowing the welds on the 200A. Something happened within the pencil itself and getting a repair response from Jovy was a dead-end. The way the base unit is made, it can't be opened as it is sealed and the pencil is hard-wired to the base, unlike others that are dis-connectable.

It served its purpose at $100.

Video for the iSolder 40
https://www.youtube.com/watch?v=8yl3BaCRzBk

No solder kit is complete without one of these:

Forget that wet sponge. This brass wool pad is the way to go to clean tips without using water and a plastic sponge.
There are other versions of this same system using the brass wool ball.
« Last Edit: June 17, 2019, 07:48:28 AM by Electrickey »

Offline Argi

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Re: Noise in the amplifier.
« Reply #6 on: June 17, 2019, 12:27:08 AM »
Hello again.
  Yesterday I spoke with the technician and explained the work. He told me that he can do it. He usually works with analog synthesizers and the reflowed procedure he usually does.
I'm lucky that he's in my city, he works very well!
I know he's going to do it right!
Thank you very much for your advice and help.
Greetings.

Offline pianotuner steveo

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Re: Noise in the amplifier.
« Reply #7 on: June 25, 2019, 06:50:30 AM »
Not to get off topic, but where do you get that brass pad solder cleaner?
I am so glad that I bought an adjustable soldering station when Radio Shack closed. I think I paid around $40 (instead of $100+) and it is awesome. I have used it for repairing plastic as well as for soldering. The adjustable heat makes it so easy to repair plastic without destroying it. I also bought a bunch of replacement tips. A great investment.
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 Electrickey

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Re: Noise in the amplifier.
« Reply #8 on: June 25, 2019, 09:55:16 AM »
where do you get that brass pad solder cleaner?

Amazon sells them if you like to use them.

https://www.amazon.com/Soldering-Cleaner-Wire-type-Holder-WYCTIN/dp/B076V14SRC



When it gets full you just open the bottom cap and there will be the balls and bits of solder.

Just jab the tip of your solder pencil into the ball several times.

It leaves the tip thinly tinned and ready for use. Works like a charm.

Tip: the balls are smaller than the container so use two to fill the cup properly to make it easier to jab the solder tip in. You can also use stainless steel wool balls to help fill the cup using the brass balls as the cleaner pad and the SS balls for support.

« Last Edit: June 25, 2019, 10:37:35 AM by Electrickey »

Offline pianotuner steveo

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Re: Noise in the amplifier.
« Reply #9 on: June 25, 2019, 03:59:30 PM »
That is awesome and cheaper than I expected.

Thanks!
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 Argi

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Re: Noise in the amplifier.
« Reply #10 on: July 09, 2019, 12:17:13 AM »
Hello again.
 Yesterday I received my old amplifier from my wurly 200. A technician reflowed all the welds and it worked ..... now there is no more noise and buzzing! It has been a great improvement !.
Everything I did:
- Check the electronic components of the amplifier.
- Reflow of the amplifier welds.
- Remove the ignition light.
- Check the cables of the ground points.
- Place the reed shield bar.
I hope this works for other users.
Greetings and thanks for the tips.