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shocked myself pretty good fixing synth

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shocked myself pretty good fixing synth

Postby n2design » Sat Dec 01, 2012 7:42 pm

I have an sh-09 that I bought and awhile back it started making a sound like a key was always pressed. So I opened it up to see what the deal was, and after fidling around a bit I noticed it looked like one of the contacts was bent and touching this thin metal rod. Anyways when I was flipping the top part I touched something that shocked the living shi t out of me. Just wondering if any of you guys fix synths while they are turned on? Have any suggestions? The main reason I needed it on of course was to figure out when the noise stopped. I was just trying to trouble shoot it with little knowledge so I was touching stuff with a screwdriver to see what would happen. At first I thought it was something that might of needed to be grounded, not sure why I thought that. That tinkering never shocked me or anything, it was when i touched something else flipping the top part over. So obviously there are some components that I need to be careful of. I know old tube amps can be pretty dangerous to (f) with but synths should be alright albeit could get shocked. Is this correct, or did I just get lucky?
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Re: shocked myself pretty good fixing synth

Postby Voltor07 » Sat Dec 01, 2012 8:07 pm

Some capacitors can definitely shock you. My guess is you touched a large value capacitor on a board.
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Re: shocked myself pretty good fixing synth

Postby n2design » Sat Dec 01, 2012 8:26 pm

Voltor07 wrote:Some capacitors can definitely shock you. My guess is you touched a large value capacitor on a board.


Generally is it safe to open up a synth and explore with out the risk of being electrocuted? That shock was pretty hardcore, but not a huge deal if that's as bad as it could be.. Its nothing like an old tube amp or sticking a knife in a toaster etc...

I've been building my own PC's for several years, and there's nothing in there to worry about. No problem with being shocked whatsoever.
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Re: shocked myself pretty good fixing synth

Postby thealien666 » Sat Dec 01, 2012 10:26 pm

My guess is that you must have inadvertently touched the mains wires on the PSH32 board (power supply board on the center bottom part of the synth, near the key contacts).

BTW, there is not enough voltage in capacitors inside this synth to shock you. But 120 V.A.C. from the wall outlet will !! :shock:
Suggestion: while power is off (power cord disconnected from wall outlet) temporarily tape a piece of cardboard over the lugs on the power supply board, until you fix it. Don't forget to remove it after everything is fixed properly though... :roll:

EDIT: In PCs the PSU is self-contained, and all dangerous high voltages are inside an isolating Faraday cage. Only low voltage comes out of that PSU box. But in synths, the PSU is composed of several parts, often laid out and easily accessible inside the casing. In the SH-09, the power cord comes in from the back on the right side of the synth (standing in front of the keys) and the transformer is all the way to the left side. So there seems to be a small board that receives the wires from the power cord et redistributes it to (possibly) the power switch and eventually to the transformer at the other end. That little board is where the 120 V.A.C. is exposed.
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Re: shocked myself pretty good fixing synth

Postby n2design » Sat Dec 01, 2012 11:17 pm

thealien666 wrote:My guess is that you must have inadvertently touched the mains wires on the PSH32 board (power supply board on the center bottom part of the synth, near the key contacts).

BTW, there is not enough voltage in capacitors inside this synth to shock you. But 120 V.A.C. from the wall outlet will !! :shock:
Suggestion: while power is off (power cord disconnected from wall outlet) temporarily tape a piece of cardboard over the lugs on the power supply board, until you fix it. Don't forget to remove it after everything is fixed properly though... :roll:

EDIT: In PCs the PSU is self-contained, and all dangerous high voltages are inside an isolating Faraday cage. Only low voltage comes out of that PSU box. But in synths, the PSU is composed of several parts, often laid out and easily accessible inside the casing. In the SH-09, the power cord comes in from the back on the right side of the synth (standing in front of the keys) and the transformer is all the way to the left side. So there seems to be a small board that receives the wires from the power cord et redistributes it to (possibly) the power switch and eventually to the transformer at the other end. That little board is where the 120 V.A.C. is exposed.


Thanks thealien666! Just what I needed to know, and will def. follow your tip regarding the power supply! It was on the left side, so I think you hit the nail on the head. Did you goto school for electronics, or self taught? I'd love to start buying old broken synths and fix them up, I wonder what the learning curve is like for people without a formal background though. which is harder, finding replacements parts or knowing what to do with them?
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Re: shocked myself pretty good fixing synth

Postby Voltor07 » Sun Dec 02, 2012 1:06 am

n2design wrote:I'd love to start buying old broken synths and fix them up, I wonder what the learning curve is like for people without a formal background though. which is harder, finding replacements parts or knowing what to do with them?

A little bit of both, actually. I am by no means a synth tech, but I DO know my way around a soldering station. I took AC/DC Fundamentals in high school, as well as some low-level college courses after high school. Synthesizers are fine pieces of equipment and vintage ones are particularly hard to find parts for. A lot of it has to do with the fact that IC's are constantly changing. Replacements for an SSM 4080, for example, are pretty hard to find. Solid State Microsystems went out of business years ago. The chip burners for the 4080 are nonexistant, though there is a limited number of NOS chips that can be had...for a price. Other chips, custom made by the synth companies for a specific purpose (Moog Polycom chips, for example) are very hard to find, and are usually very expensive. If you want to teach yourself, the library is your friend, as is Kevin Lightner's website. He has documentation for a vast number of synths, but you may want to learn how to read schematics first. :wink:
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Re: shocked myself pretty good fixing synth

Postby thealien666 » Sun Dec 02, 2012 3:12 am

You're welcome, n2design.

I'm mostly self taught too. Although I have had some electronics and robotics courses for my trade. I'm a millwright.

But my 30+ years of tinkering with anything electrical or electronic, and my 10 or so years spent buying, and fixing analog synths is what has served me the most.

And in all this time, I've come to realize that about 80% of the time that something goes wrong in an analog synth, it is usually due to poor mechanical/electrical contacts. Either in key contacts, or chips sockets, or switches and connectors.

The very best way to start fixing them is to get their schematics and study them carefully (as Voltor also wisely suggested). But if you have a hard time understanding it all, then you should start by reading about it. Or better yet, learn about it in a course.
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Re: shocked myself pretty good fixing synth

Postby n2design » Sun Dec 02, 2012 12:46 pm

Voltor07 wrote:A little bit of both, actually. I am by no means a synth tech, but I DO know my way around a soldering station. I took AC/DC Fundamentals in high school, as well as some low-level college courses after high school. Synthesizers are fine pieces of equipment and vintage ones are particularly hard to find parts for. A lot of it has to do with the fact that IC's are constantly changing. Replacements for an SSM 4080, for example, are pretty hard to find. Solid State Microsystems went out of business years ago. The chip burners for the 4080 are nonexistant, though there is a limited number of NOS chips that can be had...for a price. Other chips, custom made by the synth companies for a specific purpose (Moog Polycom chips, for example) are very hard to find, and are usually very expensive. If you want to teach yourself, the library is your friend, as is Kevin Lightner's website. He has documentation for a vast number of synths, but you may want to learn how to read schematics first. :wink:


Great advice Voltor. I regret not taking those classes in school. I opted for foods class, cause that's what all the ladies took. That and for some reason I always had the munchies...

I'm going to go on youtube and see what I can find. Might go ahead and see if I can take a class somewhere.
Last edited by n2design on Sun Dec 02, 2012 12:48 pm, edited 1 time in total.
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Re: shocked myself pretty good fixing synth

Postby n2design » Sun Dec 02, 2012 12:48 pm

thealien666 wrote:And in all this time, I've come to realize that about 80% of the time that something goes wrong in an analog synth, it is usually due to poor mechanical/electrical contacts. Either in key contacts, or chips sockets, or switches and connectors.


Do you buy alot of broken synths on ebay? That would be a fun hobby.
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Re: shocked myself pretty good fixing synth

Postby thealien666 » Sun Dec 02, 2012 2:19 pm

n2design wrote:
Do you buy alot of broken synths on ebay? That would be a fun hobby.


I've never bought any synth off eBay. But many locally. I always want to be able to try it before buying it, to get an idea of what will have to be done to repair it.

Fixing analog synths can be fun, but it's always time consuming and rather expensive. Unless you can sell it back for a small profit once fixed, if you know what you're doing of course. If you don't, you'll most probably end up with a non-working synth and a rather expensive pile of electronic parts...
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