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Yamaha A-1000 Repair and Info Thread

Discussion in 'Yamaha' started by tmsears, Apr 13, 2017.

  1. tmsears

    tmsears Active Member

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    Thanks, I am a pretty good hand on soldering from doing tonearm rewires, etc. in the past, but I have never had the task of doing so many at once. Thanks!
     
  2. tmsears

    tmsears Active Member

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    Here is the parts list I used to order from. I think it is sorted out pretty well:

    A-1000 Parts List.zip
     

    Attached Files:

  3. ic-racer

    ic-racer Well-Known Member

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    790
    Location:
    USA
    Looks like you have things figured out here, if not already repaired. I went through this just about a year ago. Here is the thread, in case it has any additional information.
    http://audiokarma.org/forums/index.php?threads/yamaha-a-1000-dsbg.711073/

    To save some reading, after cap replacement, I still had issues. I did extensive diagnostics, but in the end, re-flowing every single solder connection on the main board solved all problems. I can report that since my repairs, my A-1000 has performed flawlessly. I'm listening to it right now.

    Looks like you have a Power Amp to repair also. I repaired my M-45 back in 2012 and it is still working fine: http://audiokarma.org/forums/index.php?threads/yamaha-m-45-m45-repair-popping-no-output.424327/
     
    Last edited: May 6, 2017
  4. tmsears

    tmsears Active Member

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    Actually, I haven't started it yet. I have all the parts ordered save one but have some personal/family issues I am having to deal with right now. Hopefully I be able to dive into it mid next week and when I do I will post pictures documenting my progress.
    But thanks for for the solder tip, as others have mentioned. In fact. I have seen it mentioned so often on these forums that it seems like it is a really persistent issue with these Yamahas, and I am wondering what causes it. Is it heat? crappy soldering job at factory? bad solder? all of the above? Yes, my M-4 has alot of DC on one of the channels so it is out of service, which is ironic, as the A-1000 was going to do fill-in duty.
     
  5. zaibatsu

    zaibatsu Active Member

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    315
    Parts list looks good, let us know how you get on when you get around to it.

    I don't think Yamaha is worse than anything else in terms of the soldering work, hard to make guesses on the original solder used - obviously low lead content can be problematic which is why I suggested using 60/40 or 50/50 and making sure you add a little fresh solder to each joint. I think the heat is a big factor though, the better Yamaha amps (especially these Class A ones when run in that mode) generate a lot of heat, and in fairness the thing is 34 years old. The high-end amps prior to the switchable Class-A (i.e. only one bias setting) tend to run pretty high bias as well. Good for sound, bad for heat. Finally, unless you're the original owner, it's hard to know how it was used in the past - many owners stack other gear on top of their amps, a big no-no with these in particular.

    Once you've done the job properly, given reasonable ventilation, the amp should last for a very long time.
     
  6. tmsears

    tmsears Active Member

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    Well, I got to work a little on this beast this week, not near as much as I would've liked but I did get the resistor network board AKA the "BBQ board done:
    IMG_20170518_245712529.jpg IMG_20170518_014832736.jpg IMG_20170518_032305547.jpg IMG_20170518_032331828.jpg IMG_20170518_032931683.jpg

    I decided to work on the main "equalizer" board next, starting with reflowing the solder joints, which is proving to be challenging because the solder used on this unit is the crappiest stuff I have ever seen. On every joint I have encountered, either the joint is broken or the solder literally "deflates", like a tiny souflet when I heat them up. Some of the joints I have been able to just touch up by adding some 60/40 like #zaibatsu suggested but on about 30% of them the old solder won't flow together with the new and I have to remove the old stuff to get a clean joint. Not complaining mind you but it looks like this is going to take longer than I had anticipated :idea:. More pics to follow as I progress. :D
     
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  7. zaibatsu

    zaibatsu Active Member

    Messages:
    315
    Nice work, looking forward to the finished product!
    That's exactly what the solder joints are like - it's just a result of the heat I reckon. I rebuilt a Technics amp recently from the same era / output power, and the solder joints were all mint - but heatsink area was probably 1/3 of the size, ran quite cool, and the SQ wasn't in the same league.

    I found most of the joints took new solder fine, but in hindsight, I've been using quite thick solder which is a pain to work with but has a thick core of flux which must have mitigated the issue you had. They definitely do deflate and disappear like you describe, that's why I suggested it really is worth redoing every single joint if you have the time, they're all "on the brink". In 50 years someone will be stoked with your efforts. :D

    I purposely leave my joints a bit bigger (looks like exactly what you've done) to give them a bit more heat dissipation area in the future.

    For future reference, I found a good replacement for overheating factory resistors is the Vishay PR01 series, 1W power handling in std 1/4W package (and cheap). Only thought to do this recently as these guys get super hot (part of a voltage divider bringing 70V down to 18V for the input stage). They barely get warm now.

    res.jpg
     
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  8. tmsears

    tmsears Active Member

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    Will definitely keep the resistor tip in mind for the future. Hopefully the metals will do for now.

    I made some more progress last night:

    I found a hairline crack in the main equalizer board, on the component side. Luckily the printed circuit side looks to be ok, so I put some epoxy over the crack and let that dry:
    IMG_20170519_181706028.jpg

    I also pulled the 4 1,000uF caps to remove the glue of death and tested them, all were holding only about 518uF so I went ahead and changed them out, along with the little bi-polars which tested good, I will keep them aside in just in case. Also finished reflowing the solder joints and cleaned it:


    IMG_20170519_234557459.jpg IMG_20170519_181712998.jpg IMG_20170520_015240680.jpg IMG_20170520_015220573.jpg
     
    Last edited: May 20, 2017
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  9. tmsears

    tmsears Active Member

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    I am having trouble cleaning the push button switches. I am trying to get the deoxit into them through the fronts, but I am not having any luck; they also don't seem to have any side holes that I can exploit like similar switches I have cleaned in the past.

    Any ideas/tips?
     
  10. zaibatsu

    zaibatsu Active Member

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    315
    I found if you tip them backwards at a 45 deg angle and spray a little at a time into the top of the spring where there's a slot (while pumping the switch slowly) it works its way in. Helps if you hold the switches or amp tipped backwards with something else so you can use one hand to actuate the switch and one to spray.

    Solder work looks really good. I did find on one of my amps two of the 330uF caps were down to 160uF so maybe worth checking those too. 275-285uF is average/healthy.
     
  11. tmsears

    tmsears Active Member

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    Some more progress, I got the speaker terminal board and the speaker selector/fuse board touched up with new solder and then cleaned:
    IMG_20170521_182801792.jpg

    Then I decided to make a gloriously stupid mistake. I decided I needed to "pop open and clean" the power switch.. Here is a picture of it nearly fully reassembled after about 2 hours of figuring out how to put it back together and finding a all of the parts:
    IMG_20170521_193428392.jpg

    Also not shown here but worth mentioning: I cannot emphasize this enough; don't try to open the low voltage switches to get deoxit in them. I got lucky on a few but I spent an hour repairing one that I mauled the internal copper "clamps" that ride the "rails" inside it. It was not fun trying to reform the copper, which is about as thick as aluminium foil, and then re- assemble the switch, check that it works properly with a volt meter, then have to open it back up again after you have found out that it doesn't work...:no: so, don't do it, kids. Just be persistent and work at getting the deoxit in there like #Zaibatsu suggested.

    At the end of the day I did manage to get all the switches and pots cleaned, and I am starting in on re-assembling the front side of the amp: IMG_20170525_172231048.jpg IMG_20170526_222030842.jpg IMG_20170526_222039576.jpg IMG_20170527_020310668.jpg IMG_20170527_020317194.jpg
     
    Last edited: May 27, 2017
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  12. zaibatsu

    zaibatsu Active Member

    Messages:
    315
    Some glue fun, before and after:

    DSBG_before.jpg

    DSBG_after.jpg
     
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  13. tmsears

    tmsears Active Member

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    The progress continues. I got the front end of the Yamaha buttoned back up:
    IMG_20170527_020317194.jpg

    I got the replacement relay installed. Here is a pic of it if anyone needs to reference it in the future:
    IMG_20170528_174110434.jpg

    I also got the areas on the main amp board that had all the glue on it cleaned off. Here is a pic that shows the corrosion that was left over on the components that suffered collateral damage:
    IMG_20170527_020317194.jpg

    I decided to check the main 33,000 and 22,000uF power caps with my little capacitor tester, I know it can't test them to full voltage but it gave me an idea of what shape they are in. Looks to be respectable:
    IMG_20170528_174442466.jpg IMG_20170528_175507758.jpg IMG_20170528_180035338.jpg IMG_20170528_180118214.jpg

    More info shortly.
     

    Attached Files:

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  14. tmsears

    tmsears Active Member

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    Working on the main amp board now. Here is a pic showing the corrosion still left on the nearby components, which I will be replacing shortly:
    IMG_20170528_174140860.jpg
     
  15. zaibatsu

    zaibatsu Active Member

    Messages:
    315
    I got lucky with the 1000, lots of parts were slathered in glue but hadn't corroded, one jumper was the main board victim count.

    Wasn't so lucky on one of the 700s, got around to replacing some victims recently (the diode legs crumbled as I took them out!):

    dsbg_closeup.jpg dsbg_before.jpeg dsbg_after.jpeg

    I think it's to do with the humidity the glue is exposed to in different previous homes.
     
    Last edited: Jun 2, 2017
  16. tmsears

    tmsears Active Member

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    I think you are right about the corrosion. What the glue starts, the humidity finishes.
     
  17. tmsears

    tmsears Active Member

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    Just finished re-capping and replacing corroded jumpers and resistors on the main amp board. I decided to go ahead and replace the funny blue-bodied carbon film resistors that had corroded with metal films, as they were mounted raised off of the board for reasons unknown, hopefully that should be problem:
    IMG_20170530_244713230.jpg

    I tried replacing nearly all of the low value electrolytics with wimas, but as you can see, not all of them I could get to fit, so I used regular nichicons in those areas: IMG_20170601_140255830.jpg

    Here is the result of the recap showing where I was able to get the wima poly caps in, plus the new bigger (power filtering?) caps:
    IMG_20170601_151755473.jpg

    It's slowly starting to come together:
    IMG_20170601_170755290.jpg

    I and now I am at the point where all I should have left to do is to reflow the solder joints on the main amp board and to re-grease the main power transistors onto the heat sinks:
    IMG_20170602_013807755.jpg
     

    Attached Files:

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  18. zaibatsu

    zaibatsu Active Member

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    315
    Looks good! Hopefully it will come right out of protection once you're done.
    What values are those funny resistors? Do they get hot? I might put them on my list as well. The layout is definitely pretty tight in those back corners.

    I'm planning on replacing those tubing-covered resistors with higher wattage items and ditching the covers, just don't really like them feeding their heat into the board tracks even though it's probably not a huge deal. I'd rather they were dissipating into the air than the tracks too. I think the BBQ board is actually a good idea, it stops them deteriorating main board components/joints.

    Just redid mine:
    BBQ_board_sm.jpg
     
  19. tmsears

    tmsears Active Member

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    Nice job! I don't know about the big resistors; not knowing any better I always assume that the manufacturer had a reason for doing what they did. Your board is a lot less crispy looking than mine is. Did you use metal films or carbon? Looks like carbon but I'm a newb so.. also, did you raise yours up off the board any? I can't tell from the pic.
     
    Last edited: Jun 3, 2017
  20. tmsears

    tmsears Active Member

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    That is the mystery, I assume they do,but I never got a chance to check before the amp died. They are 820 ohm so I would not think that it would generate a ton of heat, but I am still learning..
     
    Last edited: Jun 4, 2017

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