Yamaha M-80 Schematics Please O Please! - diyAudio
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Old 13th April 2006, 06:50 AM   #1
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Default Yamaha M-80 Schematics Please O Please!

Movin' on up... to a new monster fixer-upper.

Now that I'm ready, I pulled out my M-80 (amp that is...) and it almost killed me to see how close to blowing up (again) it might have been. The thing works fine, sounds unbelieveable (my fav), but it is so full of crud from the previous owner who ripped me off for it, and then 2 lousy repair jobs. All I added was a bit of extra dust.

If possible, I'd love to see some schematics, just in case some parts need replacing (like the relays, that I can't find anywhere)...

Things that need fixing...

- speaker post plates are all cracked up due to the age of the plastic. will have to find a way to make a mounting plate for the circuit board, and see if I can incorporate new binding posts.

- the speaker circuit board also has dirty or pitted relays soldered on, will have to manually clean or replace

- The main drive board is cruddy. would like to put the thing in a dishwasher full of rubbing alcohol... but may just blow a box of q-tips on it. Can't see markings on some parts.

- Main board big 1000UF caps, might have leaked??? Not sure... Might just be thick black-ish paint that became brittle; used to stabilize the caps. Thing is it looks to have spread onto nearby resistors, etc... (will take a picture ASAP) Caps look fine otherwise.

- the thin upper transistor rails are warped! (boards are too thin) with lousy soldering. May not touch since it's working OK. Will just clean.

- Power section seems fine

- not sure if I found the bias pots, or just input level adjustments. Really old type... but since stable, may not touch.


That's my ideas up to the moment... If anyone has experience working on these, I'd greatly appreciate any tips. The sound is phenominal, but I don't want to risk my favourite speakers on it anymore... at least until I feel it will be reliable.

Cheers!


---> Looking at the M-80, makes me think that Hafler had the right idea making the amps so simple. Wish I could swap transistors. The Yamaha - Sanken ones are so mellow sounding. Probably worth more for parts alone.
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Old 13th April 2006, 02:11 PM   #2
anatech is offline anatech  Canada
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Hi bluesmoke,
I used to do warranty one these. Nice sounding amp.

That black stuff is just glue, relax. Blow it out with an air compressor first. If you want to clean the board, remove it and dismount the heatsink mounted parts. Remove the pots and lable for position and clean away.

The paper copies of the manual are not expensive from Yamaha.

I really hate messy / poor servicing jobs. I usually remove the larger parts and clean up the PCB's, then remount. It is a sure bet that the heatsinks could use cleaning and all power semi's should be regreased. You may need new insulators from what I've seen come back from the field.

-Chris
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Old 14th April 2006, 07:17 AM   #3
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Hi again!

Yup, I'd give Yammy a call and see what they are asking for the service guide... was thinking there might have been a pdf version floating around by now. I probably won't really need it if I just tinker on the speaker out relay boards.

May just spend a week blowing air and q-tipping the main boards. Looks like a mess with the spider of wires going everywhere, and a lot of them aren't quick-release. If I start pulling things off the heatsinks, I may be asking for trouble (with my luck and skill). The mounting job seems to have been done well. Will attempt a little bit at first to see if it's manageable.

If I think about this too much, I may end up selling the thing for soneone else to fix up... But I do love it's sound. ... ... maybe it will just rest in the closet for a while...

Yeah, and about lousy service jobs... seems I have experienced them all... Including a wonderful "to cheap to replace the fuse, so I'll bypass the socket with some wire and leave it that way"... sadly, found it way too late to complain. Luckily nothing burned down.
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Old 17th April 2006, 09:16 AM   #4
ostie01 is offline ostie01  Canada
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Hi, bought the M-80 manual last year.Received a copy on cd-rom with the manual but it's in BMP format.Those files have a total of approx. 9 megebites but this is for 3 files (5 + 2.25 + 2.25) or I can scan the manual and make a PDF file.Let me know if you still need it.Jeff
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Old 17th April 2006, 01:18 PM   #5
anatech is offline anatech  Canada
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Hi Jeff,
If you send it to bluesmoke, can you copy me as well? That way you aren't using too much bandwidth. BMPs are fine for me.

-Chris
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Old 17th April 2006, 06:05 PM   #6
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Hi Jeff

Would you be so kind and send it to me too ? Email is coconu@zib.de

BMP is fine, but you could just convert it to JPG, PNG or some other compressed image format to reduce size.

Thanks
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Old 25th April 2006, 07:37 AM   #7
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Hiya,

Would love the manual if you're up to it.

Mega Thanks.
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