Yamaha A-1000 Repair and Info Thread

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

  1. zaibatsu

    zaibatsu Active Member

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    Yeah I'd definitely diode test everything in-circuit first (both directions) to see if you spot anything fishy or inconsistent.

    I think you can get to everything (even the 4 diodes), use some scrap wire if you need to. It's a pain to pull the caps if you don't have to.
     
  2. tmsears

    tmsears Active Member

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    Response #1 Oh...doh!

    Response #2 Education time: why would it not be one of the 4 gigantic diodes? I am sure there is a simple reason, but after double checking he schematic, but at the risk of sounding foolish, I am still vague on what their purpose is, if the big rectifier does it for them anyway?...
     
  3. tmsears

    tmsears Active Member

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    I did on the D164, but I already have it pulled "halfway out, so I have to get to the green side of the power board to put it back..any tips?
     
  4. zaibatsu

    zaibatsu Active Member

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    How'd you pull it out without desoldering from the green side?
    You might be able to get to some of the board with the iron if you take the side bar off the amp (have to hold the transformer / be careful once that brace is removed since it provides most of the structural support) but at least in my experience I had to remove the 4 caps to be able to solder on that board properly.

    I'd also diode test D167 both ways in-circuit (easy) just because I've seen that guy failed in similar amps before. Probably not the issue but worth checking.
     
  5. If the circuit diagram is correct and (RP+) equals (HB+), D164 must be OPEN circuit (AIR) and some transistors in the TR136 - TR156 ballpark must be SHORT circuit (WIRE): i.e. Something is no longer a semiconductor. :yikes:

    Yamaha_A-1000_TurboProcess.jpg

    What voltages do you measure in the coloured (I hope you're NOT colour-blind) boxes?
    Use 0V (GREEN) as the reference point.
    Check for AC (as well as DC) on the DC voltage points. :blah:
    Please post the results.

    Yamaha_A-1000_PSU.jpg

    AC voltages are boxed-out in GREY.
    DC voltages are boxed-out in VIOLET.

    Good Luck!

    EDIT: Don't forget (as I did...) to measure the plus & minus 22V rails ('x' marks the spot).

    Yamaha_A-1000_22V.jpg
     
    Last edited: Sep 10, 2017
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  6. tmsears

    tmsears Active Member

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    I heated the "bar" of solder that is on the tan side, thinking (why I don't know) that the diodes were perhaps secured that way. Using my hemostats I got on leg partially lifted when I realized that said leg was way to long to be simply attached via the "solder bar". So I stopped, turned the unit over, and saw that it was through hole mounted. I wasn't thinking very well that day; I had to put my dog down the week prior, along with some other personal disasters, and really had no business messing with it. I see that if I undo the big caps that I will be able to pull the board. If I have to do that, I might as well check all the components on it out of circuit, and rework the solder on that board while I'm at it.

    Which leaves me asking a question: How do you test the bridge rectifier? I assume using the diode test function on the multimeter, but it has four legs, so I am a little unsure on that. The diode I "partially" pulled was measuring the same voltage both ways, but I don't know if that is because of the circuit or because of the diode.
     
    Last edited: Sep 17, 2017
  7. tmsears

    tmsears Active Member

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    I will have to look at my notes Hamish, I think I tested those but I am not certain. The rest of your post I will come back to after I have finished working on the power board and have time to look over your post it greater detail. I thank you for input and suggestions.
     
  8. avionic

    avionic " Black Knights " Subscriber

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    Thats a real tough thing to do. My condolences.:(
     
  9. avionic

    avionic " Black Knights " Subscriber

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    4 pins = 4 diodes
    [​IMG]
     
  10. tmsears

    tmsears Active Member

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    I appreciate it. No, it is never easy.
     
  11. tmsears

    tmsears Active Member

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    Well, after a month long hiatus I am finally able to start, slowly working on this project again. After a delay from my solder sucker bulb's nozzle slitting in half I finally got the power filter caps de-soldered.
    The wire was corroded somehow at the turns around the posts of the caps, and so this happened:

    IMG_20171015_034627975.jpg

    I also managed to burn about 4-5 wires' insulation, so that will be fun heat-shrinking. a hot air gun is on the way.

    it's what I get for stopping and getting rusty with my dexterity :bigok:
     
    Last edited: Oct 18, 2017
  12. OMGCat!

    OMGCat! AK Subscriber Subscriber

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    I get rusty with the iron so quickly and it always irritates me the first few times.

    Good luck with the renewed rebuild!
    I am in the middle of my own A-1000 I bought from eBay with a nuked left channel.
     
  13. avionic

    avionic " Black Knights " Subscriber

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    Chernobly'd..
     
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  14. tmsears

    tmsears Active Member

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    ROFL
     
  15. tmsears

    tmsears Active Member

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    Well, I got my burned wire mess cleaned up:

    IMG_20171021_031037153.jpg

    I also resoldered the power board since the solder joints are just as lovely here as they were everywhere else:

    IMG_20171021_031011592.jpg

    I went ahead and pulled the four diodes and the two bridge rectifiers and tested them: they all measure as normal out of circuit. They all measured uniformly in circuit as well. I'm going to go ahead and put the caps back and the all the aforementioned back in.

    I'm kinda at a loss at this point.
     
  16. tmsears

    tmsears Active Member

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    With no further input, I am going to go back up the thread and review Hamish's posts. To recap (no pun intended), I checked D168,D162,D163,D164,D165,and D166, out of circuit, as in, unsoldered and on the bench, both with my multimieter's diode function and with my little chinese component tester. They all came back normal.
     
  17. tmsears

    tmsears Active Member

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    As far as what is inside the triangle you marked up on the schematic, the only components I have tested there was TR136 and TR156, with R256 and R260 which tie to aforementioned TR156. Not tested anything else. Will do once I get everything re-attached to the main filter capacitors.
     
  18. tmsears

    tmsears Active Member

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    OK, When I do these measurements, just so I am clear, I connect my negative of my muiltmeter to the chassis, correct? I apologize, but I have forgotten some of what I have learned, Life has kinda gone sideways one me recently and I am short on time, as my Dad is about to have 3 major surgeries and once that starts up I may never get back to this for a long, long time. I need my tunes! :bowdown:
     
    Last edited: Oct 25, 2017
  19. That's incorrect! Never use the chassis as a reference - it may be at a different potential (potential difference) to the 0V ref.
    Always use the designated ZERO VOLT REFERENCE point (or the common 0V between the reservoir/smoothing capacitors in this amplifier). It avoids misleading/erroneous measurements.

    Yamaha_A-1000_0V.jpg

    Good Luck!
     
    Last edited: Oct 25, 2017
  20. tmsears

    tmsears Active Member

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    OK, Sorry Hamish. That makes sense now. As I mentioned, I am having a mental block right now, but I am also in a bit of a slow, yet ever present, rush to get this repaired, due to some life changes that are about to happen to me.
    Thank you for the clarification - makes me less nervous. This unit was purchased to be a fill in substitute while I refurbished my main/only system. That was a mistake on my part, from the very beginning.

    Question, how do you measure the reference voltage to see if it is at zero?
     

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