Yamaha A-1000 Repair and Info Thread

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

  1. zaibatsu

    zaibatsu Active Member

    Messages:
    393
    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

    Messages:
    162
    Location:
    Middle of Nowhere
    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

    Messages:
    162
    Location:
    Middle of Nowhere
    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

    Messages:
    393
    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. Hamish119

    Hamish119 New Member

    Messages:
    48
    Location:
    London, UK
    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
    zaibatsu and Nashou66 like this.
  6. tmsears

    tmsears Active Member

    Messages:
    162
    Location:
    Middle of Nowhere
    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

    Messages:
    162
    Location:
    Middle of Nowhere
    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

    Messages:
    35,183
    Location:
    Fort Dodge, Iowa
    Thats a real tough thing to do. My condolences.:(
     
  9. avionic

    avionic " Black Knights" Subscriber

    Messages:
    35,183
    Location:
    Fort Dodge, Iowa
    4 pins = 4 diodes
    [​IMG]
     
  10. tmsears

    tmsears Active Member

    Messages:
    162
    Location:
    Middle of Nowhere
    I appreciate it. No, it is never easy.
     

Share This Page