Need help troubleshooting/repairing Yamaha Portasound PS-3

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Need help troubleshooting/repairing Yamaha Portasound PS-3

Postby Jaymo » Sat Mar 24, 2018 9:18 pm

I bought a PS-3 for the princely sum of $8.56 US.
It didn't have a power supply, but I have a 12 volt Dell power supply that is the correct polarity that I'm also using to power a small guitar practice amp.
Anyway, when I brought it home, only the keys on the left 1/3 of the board worked (black and white keys).
The other keys were so quiet that you had to put your ear to the speaker to hear them.
So, I took it apart and checked for burnt components, traces, corrosion, dirt, etc.
The only issue I found was that someone had been inside it before, and the shielding paper/foil was torn in two.
I've temporarily repaired the shielding with aluminum foil cut out to the exact pattern of the original shielding, and stuck to the original shielding via the adhesive on the original shielding.
The temporary shielding repair shows continuity along its length, which is much better than the damaged one.

Anyway, now I can get all of the keys to work but ONLY when the vibraphone switch is closed.
All of the other voices are so quiet that you have to put your ear to the speaker to barely hear them.
Also, I can't hear any difference between having the sustain switch open or closed.

I bought it cheaply from a used music equipment store with the sole intent of using it as a repair project.
Now, I need to know what and where to test in order to repair it.

It really is in quite good nick for its age. I've found no evidence of being dropped, nor any other damage than the torn shielding.

Can anyone here help me bring this little old keyboard back to life?
Last edited by Jaymo on Sun Mar 25, 2018 4:07 pm, edited 1 time in total.
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Re: Need help troubleshooting/repairing Yamaha Portasound PS

Postby Rasputin » Sun Mar 25, 2018 2:06 am

Luckily for you, I just posted the service manual for this a week ago. It's probably the last post in the Service Manual sticky. Or just, you know... use the search feature.
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Re: Need help troubleshooting/repairing Yamaha Portasound PS

Postby Jaymo » Sun Mar 25, 2018 4:35 pm

I greatly appreciate you posting the service manual for it.
I went straight to the schematics and tested the switches.
I started with the vibraphone switch, for a baseline, since it was the only voice working and I needed to determine which terminals were which.
OK, so it turned out to be pretty standard. Center common. Top normally closed. Bottom normally open.
Well, all the other switches had high resistance in the normally open position when said other voicings were selected.

Thinking that it was probably oxidation or dirt/dust in the switches, I cleaned and operated each switch until the normally open position of each had 0 ohms when closed.
Now, it works perfectly.
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