Yamaha M-70 Thread

Discussion in 'Yamaha' started by Bratwurst7s, Jan 17, 2018.

  1. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    I like the Fluke 77 so much that when I saw a 79/III true RMS on ebay for €80 I just bought it. Having a total of 3 multimeters going forward will be a real luxury.

    Cheers,
    James
     
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  2. Oldsansui441

    Oldsansui441 AK Subscriber Subscriber

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    I see the new power supply is being put to good use. That power button looks really good, l think they naturally lose some of the orange pigment out of the plastic button over time, mine is the same.
     

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  3. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    Yep. I'm already having fun with the PSU. Today I took a 1k trimpot and tacked it to a piece of breadboard so that I could play around a bit.

    I also took a few of the LED's to work with me today and chucked them in the drill press and filed the flanges off of them. Now the fit all the way into the rubber glove and it looks a lot better, the yellow spots aren't showing up now.

    After presetting the pot to 500 ohms I tried some different settings, drawing from 10mA to 30mA and actually I couldn't see much of any difference until I really cranked it past those limits. At around 500 ohms it's bright enough to see in daylight with all of the room lights on but not blinding in the dark. I think that I'll just stick with the 510 ohm resistor.

    Next up is the flat face 100° parts. I'm going to try them for the meter scale backlights. They aren't as bright, I think 1800 mcd instead of 4000 so I don't know if they will be bright enough. But I know how to find out now. :)

    DSC05239.jpg DSC05240.jpg DSC05241.jpg

    Cheers,
    James
     
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  4. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    The binding posts look really nice. Nice and clean, they look almost like originals from an AX series amp.

    How does the M-50 sound? I got many years of enjoyment out of mine. One of the dumbest things that I ever did was get rid of it. After 3 months of on/off working on the 70 I'm starting to get seriously ready to listen to it.

    Cheers,
    James
     
  5. morfeora

    morfeora New Member

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    Seams have been a lot of progress here James, pretty glad to see your hard work is giving good results, as should be. :beerchug:

    Cheers,
    Rodolfo
     
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  6. avionic

    avionic " Black Knights " Subscriber

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    Warm white - cool white -- still to bright for that orange colored grommet. I've been using amber colored " water clear" diodes.
     

     

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  7. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    I may try one of the 1800 mcd in there next just to see how they look.

    Do you have a Mouser reference for what you've been using?

    Cheers,
    James
     
  8. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    Hi Rodolfo! Yes, things are starting to come together. I think that I'm about 2 weeks away from being able to try it out.

    How are the speakers sounding?

    :beerchug:
    Cheers,
    James
     
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  9. avionic

    avionic " Black Knights " Subscriber

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  10. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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  11. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    Well, the RCA's and speaker posts arrived yesterday. The good news is that the binding posts will work. The bad news is that the RCA sockets won't.

    The panel cutout for the inputs works as far as width goes (need 11mm, is 12mm) but the vertical distance won't. Need about 30mm but have 26mm. The problem is that the insulating bushings and fixing ring have too large of a diameter. I would need to file (etc) the slot longer to make this work and I really don't want to make any such attacks on the case. So I'll have to look again. This is more of a luxury than a must do and can be done later without having to tear the entire unit apart.

    The speaker binding posts will work just fine. There is one small issue to deal with but I'll explain that tomorrow.

    Because of the overall diameter of the posts I decided to make an adapter plate to mount to the inside of the case to support the posts. I made that today and it turned out well. I'll make a complete explanation tomorrow but in the mean time here is a teaser photo.

    DSC05244.jpg

    Cheers,
    James

    edit 24 April 18: See post #251 for a sketch of the plate with dimensions.
     
    Last edited: Apr 25, 2018

     

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  12. Oldsansui441

    Oldsansui441 AK Subscriber Subscriber

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    Thank you, appreciate that.

    I have only had it running for approx 1/2 hour tonight so can't really give an honest opinion yet but seems to perform well. Adjusting the pre amp bass pot caused some occasional woofer oscillation so l will have to go back in and sort this out :mad:. Bet you are really keen to have a listen after all of your work.

    Yes l am with you on this on trying to keep the rear panel cutouts original.

    Nice work on the panel, looks familiar to me from a few days ago, haha. I had to trim a couple of mm of the bottom of my binding post panel because l didn't allow for the little right angle part of the inner frame because l had the main rear panel off.

    Here is a photo of the power light on the C-50, it is noticeably more orange than that on the M-50. I replaced the globes in both. I said in an earlier post that the button loses it's orange colour, l meant the little rubber boots. Strange thing is that l pulled the boot out of the C-50 completely to inspect and it isn't orange at all but rather a cream colour.
     

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  13. avionic

    avionic " Black Knights " Subscriber

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    The amber LEDs I posted. DSC04178.JPG
     
    Last edited: Apr 13, 2018
  14. avionic

    avionic " Black Knights " Subscriber

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    The green is warm white with OEM green boot.
     
  15. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    They look really good. I'll be making a Mouser order in the next week or 2 and will order some. In the mean time I'm going to use some of the flat top ones that I have. The way that I'm installing them they won't be any trouble to change. I'm using a small piece of breadboard as an adapter, mounting the resistors to it with wire extensions.

    DSC05273.jpg DSC05275.jpg DSC05277.jpg

    Cheers,
    James
     
  16. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    I was a but worried that I had measured correctly and in the end came very close to having to file off some of the bottom of the plate. It fits but just barely. I used 3mm thick aluminum because I wanted it to be thick enough to drill and tap M-3 holes for the mounting screws. That worked but if I was to make another one I would make the plate 1mm shorter, it just barely passes above the main PCB.

    The power switch boot in the M-70 is also cream colored. I'm guessing that the light bulb is also just yellow enough that when combined one ends up with the yellow power light.

    DSC05249.jpg DSC05252.jpg DSC05253.jpg

    I mounted the speaker-A posts with the holes vertical but installed the B posts with the holes angled out at about 45° to make it a bit easier to get wires into them. That means making darn sure that the wires aren't too long, but that's always the case anyway.

    Notice that the clear plastic bases aren't clear any longer. More on that in the next post.

    Cheers,
    James
     

     

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  17. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    I mentioned earlier that there was one small complication with these binding posts. I measured the panel cut-outs at 18.45mm. The clear plastic bases are 20mm. But I wanted to be able to remove the back panel without having to de-solder the posts so they must be able to pass through.

    So I found a M-8 allen head bolt and used it as a spindle. Took a half round jewelers file and filed the flats in the center hole round and mounted the bases on the spindle. Then I put that in the drill press and filed the bases down to 18mm.

    DSC05258.jpg DSC05259.jpg

    I only had 400 grit sandpaper on hand so I couldn't get them very smooth afterwards, but they do have the positive attribute of working as intended.

    Cheers,
    James
     
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  18. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    The holes in the PCB for the old binding posts are 2mm so there was just enough room to use 1.5mm² wire. I had just enough of a small scrap of silver plated wire to use for the A posts, the B posts had to settle for plain OFC wire. It was a bit difficult to guess what was long enough to work with while not being too long, but it worked.

    DSC05255.jpg DSC05260.jpg DSC05262.jpg

    Cheers,
    James
     
  19. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

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    So the binding posts are mounted, the pcb has been re-flowed, de-fluxed, inspected and re-installed. The heat sinks and pre-drive board are back in and everything re-soldered.

    DSC05263.jpg DSC05265.jpg DSC05268.jpg

    That's all of the pics that I have for today, I'll take some more tomorrow. I actually have the meter board re-capped now also and am part way through with re-flowing it. I might get as far as turning it on tomorrow.

    Cheers,
    James
     
  20. Oldsansui441

    Oldsansui441 AK Subscriber Subscriber

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    Yes there is not much room between the lower binding post mounting holes and the PCB or that right angle brace.

    Yes, it must be the combination of the two.

    Very clean work Bratwurst7s, l like it a lot :thumbsup:. Those little allen heads bolts look very neat also. Good call on turning the clear bases down to allow pass through on the rear panel.
     
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