Ba2000 right channel sounds very distorted

Discussion in 'Exclusively Sansui' started by sansuibutch, Jan 18, 2016.

  1. sansuibutch

    sansuibutch Active Member

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    372
    The right channel sounds very distorted. The volume is there but the more I turn it up the more it distorts. Is there any potential or common problems with these that would cause that?
     
  2. sansuibutch

    sansuibutch Active Member

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    372
    I cleaned the speaker output relay and it did not seem to help much.. this is really bumming me out and I know it's somthing stupid I'm overlooking. The amp cranks just the right channel is a little distorted. If anybody out there could give me a little help I'd be very greatfull
     
  3. sansuibutch

    sansuibutch Active Member

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    372
    On the right channel the DC offset bounces around between -6mv to 0mv ( Never really settles) and the right channel is right at 11mv. I tried to test the bias per service manual but the numbers I'm getting aren't even close to spec..they call for around 100ma. On my meter I'm only getting between 3.5ma and 5.5ma.. hope this helps
     
  4. sansuibutch

    sansuibutch Active Member

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    372
    Can I get any help on this. I would love to know if this thing is junk or not before I continue wasting time on it
     
  5. rasenthiran

    rasenthiran Well-Known Member

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  6. sansuibutch

    sansuibutch Active Member

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    Thanx Rasenthiran, I know it's a very reputable amp. I just want to know if it's fixable. I know some of theses parts are getting harder to find. I don't think any major components are at fault. Then again I just don't know. I guess I'll have to be more patient. This thing not working correctly has me going :crazy:
     
  7. jblmar

    jblmar JBL & marantz

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    sansuibutch,
    Where are you located?
    Do you have an oscilloscope?
     
  8. sansuibutch

    sansuibutch Active Member

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    372
    I am in rochester ny. No I do not yet own a oscilloscope.
     
  9. jblmar

    jblmar JBL & marantz

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    5,571
    Location:
    Brooklyn, New York
    You have a PM.
     
  10. Overundr1

    Overundr1 AK Subscriber Subscriber

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    2,079
    Location:
    Mississippi
    Have you tried reversing the red and whit input wires to the amp to see if the issue changes sides? Also swap the speaker wires left to right to eliminate and speaker issues. Offset will move around a little bit depending on amp temperature.
    -Lee
     
  11. sansuibutch

    sansuibutch Active Member

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    372
    Are you talking about board f2630. The white wire from the switch and the red from the main fuse holder..?
     
  12. sansuibutch

    sansuibutch Active Member

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    372
    If your talking about the rca's then yes it's definitely the right cahnnel
     
  13. sansuibutch

    sansuibutch Active Member

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    372
    I had time to get this thing back apart today..I changed all the fusible resistors and took a good look around. I can't find any bad solder joints or leaking or swollen caps..I tested every diode and just about every resistor in this amp. Is there anything else I can check with my multimeter that might be suspect. I still never picked up a oscope. The last few months been a busy with a newborn baby wich is now 6 months old
     
  14. Tom B

    Tom B AK Subscriber Subscriber

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    Location:
    Bay Ridge, Brooklyn New York
    With heavy distortion on one side I would think you have either a bad 68 ohm, or 8.2 ohm, 470 ohm, or .33 ohm resistors, or an open output or two, or possibly an open or shorted transistor on the driver board. You should be able to check all of these with you ohm meter in circuit. Just make sure the power is off. Resistors are pretty straightforward, but you can compare to the other side to verify the reading is good.
    You need to isolate to see what side is bad (on the circuit board.) To do this, with the unit on, touch pin 1 and then pin 2 with your finger when the unit is on. You should hear a hum. Don't worry, there shouldn't be any voltage on those pins, but you can check them for DC volts with a volt meter first.

    Now that you identified the side, shut power and remove plug from the wall.
    Using an ohm meter on RX1 scale or as low a scale as you have, and check B to E, then B to C, then E to C. Jot down the readings. Then reverse the leads and do these tests all over again. Do this for all of the outputs , and for all of the transistors on the bad side of the driver board. Next to the reading for the questionable side transistors, take reading of the transistors on the good side. Put all of the reading together, and repost here, and we may be able to point out problem readings.
     
  15. sansuibutch

    sansuibutch Active Member

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    372
    Thank you very much Tom. I should be able to check those later..I will post back with results..thanks again
     
  16. sansuibutch

    sansuibutch Active Member

    Messages:
    372

    I'm checking the resistance between the transistors now. From b to E I can get a fast accurate reading but between any other (b to C or e to C) it takes a while to get a measurement. At this rate this would take way more time than this amplifier is worth..is there something I might be doing wrong or is this just how it it with a meter?
     
  17. Tom B

    Tom B AK Subscriber Subscriber

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    Location:
    Bay Ridge, Brooklyn New York
    The reading from B to E and B to C should be the same.
    I should have asked you what type of meter you had.
    If it is an old analog with the Needle Meter (the best for checking transistors), put it on RX1 scale and for PNP transistor, put the pos lead on the emitter, and neg lead on Base. It should read around 5 ohms. then move the pos lead to the collector and this should also read 5 ohms (usually mid scale reading). Reverse the leads putting neg emitter and pos on base and you should get no needle deflection (infinite ohms) same with pos on base, and neg on Collector. pos to emitter and neg to collector should be no deflection (infinite ohms). Neg to emitter, and pos to collector should be no deflection as well. If any reading show "0" ohms, or full deflection, the transistor is shorted.

    If you are using a digital meter it is a bit different. You need to put the meter on the diode function, and measure the same way as above. The big difference is that in forward conduction for B to E and B to C, you will get a reading like 500 to 900, and no reading when you reverse it. No reading E to C forward or reverse. Your digital meter may also give an audible beep when in forward conduction. If you get a reading of 0, the transistor is probably shorted.

    Hope this helps. I have a really old Triplett analog meter that I use, and assume everybody has one.
     
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  18. sansuibutch

    sansuibutch Active Member

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    372

    I wasnt getting any reliable reading with my meter on those. I swapped the power transistor blocks or whatever you call the final stage and the distortion stayed on the right side so Im assuming the transistors are good. I remeber a whlie back I cleaned the speaker realay and that did seem to hel a little bit. I think il try to temporarily bypass that relay to see if it helps. I can try to phm it out I guess. Are the output relays somthing that commonly goes bad?
     
  19. JOMARK911

    JOMARK911 Super Member

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    Yes , but if you cleaned it it should do the trick for a few days. You can take it out dismantle it take the moving part with the small contacts in hand CAREFULLY , and clean Polish the contacts with a Silver polishing paste. But i think the best way is to change it . Then check the driver Board, driver transistors and pre drivers. They have a tendency to fail after all these years.
     
    sansuibutch likes this.
  20. JOMARK911

    JOMARK911 Super Member

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