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Yamaha g50 112 II does not turn on after turning voltage selector

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  • Yamaha g50 112 II does not turn on after turning voltage selector

    Hey! I just found that switch on the back of my old Yamaha g50 112 II amp. Its a "Voltage Selector" where you can switch between 220v, 130v, 110v, 240v.
    I always had it on 220v and never changed it. I didnt find out what the switch is doing. Now I switched to 130v and turn the amp back on. It would make a loud signal clicking noise and then turn off again. Since then I couldnt turn it on in any voltage selector position. I didnt smell any burned circuits. I have no idea whats happening. Its completely dark, light is off, no sound, nothing.
    I have only very little knowledge about repairing these devices. Any help is appreaciated. I dont even know where to get them for repair.
    Cheers
    Last edited by Flux; 02-19-2021, 06:34 PM.

  • #2
    Where are you, what's your mains voltage?
    Why did you switch to 130V??
    If you're in a 220V-240V country, switching to 130V would (at least) blow your mains fuse.
    - Own Opinions Only -

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    • #3
      Im in europe, germany. I just didnt know what the switch is actually doing. Probably curiosity. Couldnt find much in the internet about it. So I switch it
      So you think its blown? If its the fuse, it should be repairable right?

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      • #4
        Do you know where to bring it for repair?

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        • #5
          The switch connects the mains across different primary windings. Hopefully a new 1.6A fuse will fix it.
          Click image for larger version

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          Support for Fender, Laney, Marshall, Mesa, VOX and many more. https://jonsnell.co.uk
          If you can't fix it, I probably can.

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          • #6
            Originally posted by Flux View Post
            Do you know where to bring it for repair?
            https://www.yamaha.com/paragon/servicerlocator/

            https://usa.yamaha.com/support/contacts/index.html

            https://de.yamaha.com/de/support/service_locator/
            It's All Over Now

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            • #7
              Any competent amplifier repair shop can take care of it. Surely the main fuse has blown, but possible further damage.
              Education is what you're left with after you have forgotten what you have learned.

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              • #8
                I found the burnt fuse! It was right next to the voltage selector. Very easy to replace. Ive bought a new fuse, it will arrive in the next days. Hopefully this will fix the amp. Thanks alot for your help!

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                • #9
                  Sooo fuse came today, but the amps still not working after replacing it. The lights are on, but no sound! Actually the first time I turned it on, there was a buzz sound, but the second time it was gone.
                  So all lights are there, but nothing coming out of the speaker. Do you may know the origin of this? Any help highly appreaciated! Thanks

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                  • #10
                    At this point you really would need to dive in and start measuring some components to see what has been damaged. I would expect that there is some major damage that has been done.

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                    • #11
                      Originally posted by Flux View Post
                      So all lights are there, but nothing coming out of the speaker.
                      Check (replace) fuse F3 (3AT)
                      fetch?id=812456.pdf
                      It's All Over Now

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                      • #12
                        Thanks for sharing the schematic! I will check that out this week

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                        • #13
                          YAMAHA Manuals

                          https://www.owner-manuals.com/-manuals-1-20a.html?alpha_filter_id=71

                          https://www.owner-manuals.com/G50112II-service-manual-YAMAHA.html

                          It's All Over Now

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                          • #14
                            So as suggested I checked the F3 Fuse and it was burned as well! You guys are great!
                            On the pcb next to the fuse is written 250V T2.5V, so I replaced it with the same type.
                            Now as soon as I start the amp, there is buzz sound and then nothing. I checked again and the same Fuse (F3) is burned.
                            I really dont know what else could be damaged right now..

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                            • #15
                              I believe on these the power amp is a separate module that hangs down from the chassis. I would remove this and power up. If the fuse doesn't blow you can measure DC voltage rails to see if you have a functioning power supply. On these amps instead of having +/- voltage I believe it will be one high voltage rail (about 90V) at the connector where the MA board mates with the DC board. The high voltage will be on pin 6 and pin 1 should be ground.

                              I would also recommend building a dim bulb tester if you plan on going farther into this to prevent further damage to any components. Fuses don't do a great job of protecting the components, they are there to keep you from burning down your house.

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