Yamaha A-1000 Repair and Info Thread

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

  1. tmsears

    tmsears Active Member

    Messages:
    199
    Location:
    Middle of Nowhere
    Makes plausible sense, and it would explain the hum, but I didn't have the foresight to check the voltages at the start, so probably no way of knowing for sure. This has been educational to say the least! As for condition, I think the caps are still good (I hope) but based on my limited knowledge, I think the rectifiers are shot. I don't know about the diodes, but I would replace them out of an abundance of caution if I can get confirmation that the rectifiers are shot. I re-flowed all the solder joints on the board when I had it out. I had to disconnect a few wires and put heat shrink on the sections of them that I had burned during my desoldering fiasco. :rolleyes:

    Good question. maybe @avionic or @Hamish119 or any member for that matter.

    No they are not to bad on price I don't think but I had no luck with replacements because I don't know what specs to look for/what is a tolerable range in the specs. That's why I mentioned them earlier in the thread. I am pretty good with caps, and resistors now, but semiconductors, no.

    I tested the caps when I pulled them with the china capacitance tester and they still show to be within range, so hopefully they are okay. They would be expensive to replace I would imagine.

    Hopefully they will chime in soon. But I may have scared them away! :rflmao: I have sunk so much money into this beast that I will never get back - but if I can fix it at least it will have been an education.
     
    Last edited: Nov 3, 2017
  2. OMGCat!

    OMGCat! AK Subscriber Subscriber

    Messages:
    1,878
    Location:
    San Diego, CA
    I'm watching with interest what you find out. Sounds like you might be fighting with two issues between the hum and then the bias transistor shorting.
    The one I picked up was Chernobyl'd in the normal way thankfully so no huge troubleshooting was needed on my part.
     
  3. avionic

    avionic " Black Knights " Subscriber

    Messages:
    36,824
    Location:
    Fort Dodge, Iowa
    This thread has gotten so confusing.
     
  4. zaibatsu

    zaibatsu Active Member

    Messages:
    441
    You've got two rectifiers:
    Large one should be D5FB20
    Small one should be 4D4B41, but double-check, may be something else

    I attached the data I could find for both.
    You can at least get a feel for the numbers and find some possible candidates while you wait for confirmation.

    From my understanding, Vrm (rep. peak reverse voltage max), Ifsm (forward current max), and output current should both be equal or better on the replacement part, and Vf (forward voltage) should be close to the same.
     

    Attached Files:

  5. avionic

    avionic " Black Knights " Subscriber

    Messages:
    36,824
    Location:
    Fort Dodge, Iowa
    Hardly.. I have a C-2a,C-4 and a M-2 that have priority over your 1000.
     
    tmsears likes this.
  6. tmsears

    tmsears Active Member

    Messages:
    199
    Location:
    Middle of Nowhere
    I figured you were busy, so I decided to crack wise.:rolleyes: But then again I wouldn't blame you for running away either! At least we all now know that I can blow stuff up properly. :biggrin:
     
  7. tmsears

    tmsears Active Member

    Messages:
    199
    Location:
    Middle of Nowhere
    Sorry about that. I was trying to fix the issue of 128 volts of AC being dumped out of the positive DC side of a rectifier and into the connecting main filter cap. Hamish helped be troubleshoot the voltages and they are not right in several ways, AC being where (I think?) it shouldn't be. Hoping to get it out of protect mode by replacing a resistor to fix the -22 and the rectifiers to stop the AC going everywhere, but the rectifiers are difficult for me to substitute since I don't know what to look for in the way of values.
     
  8. tmsears

    tmsears Active Member

    Messages:
    199
    Location:
    Middle of Nowhere
    Thanks much. I found the same said specs online, but the "what to look for" part has me stumped, but maybe this will help. Can you go higher in output current? I plug in the style and the output current and it narrows the results to 0 in mouser.
     
  9. tmsears

    tmsears Active Member

    Messages:
    199
    Location:
    Middle of Nowhere
    Yeah, I can't say for sure but it seems to me that the hum and the rectifier trouble was probably a "creeping" issue that probably came up fairly recently, but, that is just a guess. In my career with computers it was not uncommon to fix one hardware problem only to have a simultaneous yet completely different problem pop up at the same time or shortly thereafter - and sometimes, the problem was there all along, manifested during troubleshooting something else. I would think that would also be possible in audio repair, albeit on a different level. I'm glad yours had a more straightforward issue.
     
  10. OMGCat!

    OMGCat! AK Subscriber Subscriber

    Messages:
    1,878
    Location:
    San Diego, CA
    I haven't really added much to the A-1000 thread so I'll add how I handled my BBQ board. It seems like my amp hadn't been run much at all prior to having one channel short but I wanted to head off the board discoloration before it could take hold.
    I bought a set of lead bending pliers and used the 1 watt resistors mentioned by Zaibatsu above. The results turned out pretty nice IMO.

    image3 - Copy (4).JPG
    A-1000 BBQ Board.JPG
    A-1000 resistor.JPG
    A-1000 BBQ Board done.JPG
     
    tmsears and Bratwurst7s like this.
  11. tmsears

    tmsears Active Member

    Messages:
    199
    Location:
    Middle of Nowhere
    Very nice job on bending the resistors, a lot better than I did mine. Did you bend them that way to make sure they were all at the same height?
     
  12. OMGCat!

    OMGCat! AK Subscriber Subscriber

    Messages:
    1,878
    Location:
    San Diego, CA
    I was originally going to stick something under them to make sure they were the same height until I found those lead bending pliers. I also like the way they look with the little half bend and figure the pliers can be useful for other things as they pop up.
     
  13. tmsears

    tmsears Active Member

    Messages:
    199
    Location:
    Middle of Nowhere
    That's a pretty cool find!
     
  14. tmsears

    tmsears Active Member

    Messages:
    199
    Location:
    Middle of Nowhere
    Does anyone have any recommendations for replacement for 1.8k, 5 watt Ohm wirewound resistors? The only one I pull up are the newer epoxy dipped kind, the ones in the unit now have wide, formed legs for riased height and are of the "sandbar" variety, which I can't seem to find in either mouser or digikey.
     
  15. zaibatsu

    zaibatsu Active Member

    Messages:
    441
    https://mouser.com/ProductDetail/Yageo/SQP500JB-1K8

    This is the closest I could find in factory cement moulded wirewound type.
    I can't find the radial leg type (on mouser) in 1.8K.

    You'd have to fold legs so they come out slightly below the resistor (to match the PCB spacing).

    You could also fold the surplus leg up against itself neatly to double its width (instead of cutting) and lightly solder to provide a bit more support. With some time it could be done neatly. Don't think it really matters though, as long as you mount them up off the board the same height as the stock ones.

    Unfortunately not in stock until Dec 7th, maybe you could look elsewhere if needed sooner. Using the keyword "cement" helps.
     
  16. tmsears

    tmsears Active Member

    Messages:
    199
    Location:
    Middle of Nowhere
    Yeah, I usually filter my search results to only show parts in stock, so that would explain why I couldn't find any. Neat idea about the leg folding though.
    Would the epoxy dipped type work if I increase the wattage to, say, 10 watts?
     
  17. OMGCat!

    OMGCat! AK Subscriber Subscriber

    Messages:
    1,878
    Location:
    San Diego, CA
  18. zaibatsu

    zaibatsu Active Member

    Messages:
    441
    I'd go with that ^^
    Otherwise yeah, just run the highest wattage epoxied wirewound that'll fit, 10W is fine.
     
  19. avionic

    avionic " Black Knights " Subscriber

    Messages:
    36,824
    Location:
    Fort Dodge, Iowa
    Whats wrong with the OEM resistor ?
     
  20. zaibatsu

    zaibatsu Active Member

    Messages:
    441
    Fried apparently:
    cement.png

     
    tmsears likes this.

Share This Page