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I have a M-50 Yamaha power amplifier that when I turn it on nothing happens. I opened it up and checked the fuses on the boards. None of them was blown. I checked the power going to the Transformer and the way I checked it was White to Brown(read 0 volts) and White to gray (read 0 volts).This unit has a GA6418 Transformer. If it is possible you can give me the proper voltage on the primary side (White, Brown and gray) and the secondary (Purple,Gray,Blue,Orange,White,Black and Red).I also Need to know how the LC 72760-1 and the LC 72760-2 boards control the Transformer because I think the problem is in the boards.Is there any way I can get the prints of the two boards so I can Trouble Shoot it better? I know this is a old unit (1982) but I would like to get it back working. If I need a component, do I order parts thru you?

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Posted on Jan 02, 2017

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SOURCE: Yamaha RX-V995 no power no audio [dead]

sounds like a short in the cpu of the unit

Posted on Mar 07, 2008

  • 1 Answer

SOURCE: yamaha m60 power amp

Posted on Mar 21, 2008

  • 4102 Answers

SOURCE: re sent wire diagram gat all messed up

have we spoke before in previous post?
the red can go to any 12v live peramanent such as wire to clock or other item that has power with ignition off and the same with the yellow if your putting these to the same permanent live say from clock you can join these to together red/yellow to red on clock
the black can go to any metal or neg wire.
This should then have your device working the only problem im looking at for you now is the pink wire as this stops you using the device whilst driving as it goes to handbrake but i need to find out if its live or negative.
You could just wire the red/yellow to live and black to earth then see if it switches on and works if not then let me know and ill see about the pink wire ok
Makes sure you use inline fuses on the live wires so as not to short the device out.
Make sure you know what is permanent live to put the yellow/red wire to.
It doesnt need to be ignition it only says this so you cant use it with ignition off but you can wire it into any live feed from clock or switches so its up to you what to wire it to its just the pink wire im concerned about.

PINK: does it tell you to put it to live or earth on handbrake switch?

let me know ok

Posted on Apr 21, 2008

  • 1512 Answers

SOURCE: Yamaha P-4500

Hi radek

If it is a toroidal,they have a nasty habit of going shorted turns on the primary. Is it blowing fuses? Let me know

ex In'gill ;)

Posted on Sep 12, 2008

  • 4234 Answers

SOURCE: Bose SA-3 Amp / Blown Fuse

The problem is not the transformer. You now have shorted output transistors at the very least. By corssing the wires you presented a zero(0) ohm impedence load to the output section. It quickly went into overload. Before the fuses had a chance to open up, the outputs fried. This unit will require new output transistors and perhaps the previous driver circuit will require parts as well. Figure on $20-$50 in parts plus hte local labor rate for the repair.


Posted on Oct 01, 2008

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Your post isn't clear on whether the entire system is dead, or just the radio. I'm assuming the amplifier itself is not working. Verify that you have power on both ends of the fuse with a 12 Volt tester or voltmeter. A fuse may look good, but a small break isn't necessarily visible. It's also possible given the amount of power you're running that a fusible link upstream from the fuse is blown. A blown fuse generally indicates a problem with the amplifier; don't waste money replacing it until you've repaired the amplifier.

If you have power there, check the wiring to the stereo. Perhaps a connection failed, or if the wiring is smaller than 8 Gauge, it burned out (this would most likely happen at a connection).

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If the audio output stages look good, check the inverter power transistors for shorts between the drain and source terminals.

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Hi radek

If it is a toroidal,they have a nasty habit of going shorted turns on the primary. Is it blowing fuses? Let me know

ex In'gill ;)

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