Author Topic: Yamaha M-70 massive damage  (Read 537 times)

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Offline czarlzTopic starter

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Yamaha M-70 massive damage
« on: October 23, 2024, 07:05:59 pm »
Not quite sure what happened here! For sure the fuse did not have a chance to say a word.

Have you ever seen parts (PCBs) for M-70? Those PCBs are so damaged that I would have to make them from scratch.
 

Offline Swake

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Re: Yamaha M-70 massive damage
« Reply #1 on: October 24, 2024, 04:30:13 pm »
Well.... thanks to some material regulations the house did not burn down. The other good news is that the PCB's still seem to be in a good enough shape that you can copy them. Hope you have a schematic, because whatever that black blob was before it is not going to be easy to identify.
When it fits stop using the hammer
 

Offline amyk

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Re: Yamaha M-70 massive damage
« Reply #2 on: October 25, 2024, 02:58:07 am »
Lightning strike?

Schematics, service manual are easily found online. It's not a complex circuit. Whether it's worth repairing (restoring?) and parts availability is a different question.
 

Offline Gyro

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Re: Yamaha M-70 massive damage
« Reply #3 on: October 25, 2024, 09:13:30 am »
It looks as if it's a big PIO (Paper In Oil) capacitor in the power supply mains filter... and they have a reputation for blowing up in 230/240V supply regions...

https://www.audiokarma.org/forums/index.php?threads/yamaha-a-760-a-760ii-a-960-a-960ii-a-1060-m-50-m-70-and-b-6-220-240v-warning.154682/

It sounds a bit like a massive Rifa PME on steroids - with added oil and probably not hermetic.


EDIT: From the service manual, it looks like C607, 470nF 250V, across the line, maybe it is an ordinary Rifa PME X Cap, difficult to judge the size and shape now. It looks as if that whole assembly is a Triac phase control regulator feeding the mains transformer primary. Yuk!
« Last Edit: October 25, 2024, 04:54:12 pm by Gyro »
Best Regards, Chris
 


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