BA-5000 with Issues

Discussion in 'Exclusively Sansui' started by Fhamre, May 3, 2018.

  1. Fhamre

    Fhamre AK Subscriber Subscriber

    Bought a BA-5000 a few months back. It was demo'd for me and was working fine at their home.
    Carted it home and put it under my bench till I could get at it to restore. Worked on one back in 2011.
    Yesterday I put it on my bench,ouch. Took off most of the covers to get a look at the unit and see what might have been done to it.Judging by the screw damage it has been opened many times. Can see the driver boards have been recapped and the odd cap replaced on the power supply etc. Typical crap capping just using what they had on hand. I took photos and pulled the right driver board to examine workmanship. I've seen worse.
    Put the board back in. Checking my pictures to ensure correct wires attached. I like to try determine/adjust amp (bias)as per service manual before starting the restoration.So I hooked it up to my dbt( only 150 watts) and tried to see where things are at.Well the lamps stayed bright and I didn't see the power light or meters light up.
    Quickly shut off.Checked unit over again. Read the suggestion that the amp works best with 300 watts on the dbt.Knowing that the unit was working I thought that perhaps the low watt DBT was the issue.
    So I tried without the DBT. Not a good idea. Didn't leave it on long. No meter lights or relay click etc. But a slight smell to suggest something is not happy.
    So went out and found two 150 watt bulbs and put them in the DBT. Checked all the fuses I can see.
    Plugged it in without the driver boards and nothing. No flash,no power meters ,nothing.
    Looking for suggestions.
     

     

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  2. kevzep

    kevzep Its all about the Music Subscriber

    Well with something like that which seems to have a dead short, I'd start by measuring the bridge rectifier.
    Work your way in from there.....
     
  3. Fhamre

    Fhamre AK Subscriber Subscriber

    Well I am only seeing 4V and -4V coming off the PS caps instead of 63V.
     
  4. kevzep

    kevzep Its all about the Music Subscriber

    Yeah, check the Bridge Rectifier, don't fire it up any more until you find out why this is happening, further damage may occur.
     
  5. Fhamre

    Fhamre AK Subscriber Subscriber

    How do you test a bridge rectifier?
     
  6. petehall347

    petehall347 the brandy coffee man Subscriber

    Messages:
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    havent a good schematic here but i guess meters run off the amps which are removed so nothing much will happen with them . the lights are maybe just a bad fuse or because the power is being dropped by the short circuit you need to find the short with your multimeter with power removed .
     

     

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  7. Fhamre

    Fhamre AK Subscriber Subscriber

    It must be something simple. The unit worked before it got on my bench.
     
  8. avionic

    avionic " Black Knights " Subscriber

    Messages:
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    Location:
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    Like 4 diodes
     
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  9. petehall347

    petehall347 the brandy coffee man Subscriber

    Messages:
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    test as 4 diodes ...
    i dont think this is the problem though ..test anyway to be sure . [​IMG]
     
  10. kevzep

    kevzep Its all about the Music Subscriber

    Same as testing a diode, so use the diode function on your DMM, and check for forward voltage drop.
    It will be painfully obvious if its shorted.

    If you take a picture of the power supply area we might be able to see the Bridge Rectifier and point you in the right direction.

    although, having said all this, if the bridge rec was blown it would take out the mains fuse, but I would check anyway...
     
  11. avionic

    avionic " Black Knights " Subscriber

    Messages:
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    Might be shunted rather than shorted.
     

     

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  12. Fhamre

    Fhamre AK Subscriber Subscriber

    Here is a pic. I do have a Peak Analyzer.
    IMG_1599.JPG
     
  13. petehall347

    petehall347 the brandy coffee man Subscriber

    Messages:
    26,803
    Location:
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    just in case be sure its set for correct mains voltage .
     
  14. kevzep

    kevzep Its all about the Music Subscriber

    He's seen and heard it working before....
     
  15. petehall347

    petehall347 the brandy coffee man Subscriber

    Messages:
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    Location:
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    exactly ..it worked at someone elses place and not his .. just looking for obvious things first . only thing i have seen turn into a resistor from standing is capacitors . resistors can go open . semiconductors are not very likely to short out from lack of use . bad cap may well cause it to happen though . i know some places have 2 voltage choices . 220 or 110 or similar .
     
  16. Fhamre

    Fhamre AK Subscriber Subscriber

    Well it is a local unit so no change there.
     

     

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  17. petehall347

    petehall347 the brandy coffee man Subscriber

    Messages:
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    main filter capacitors might be having a bad day .. never had it happen myself but anything can happen .
     
  18. Fhamre

    Fhamre AK Subscriber Subscriber

    I'm not getting voltage on F-2519 the power supply board.
     
  19. kevzep

    kevzep Its all about the Music Subscriber

    I'd check your AC voltages coming out of the transformer, then work towards the supplies from there.

    You have checked the mains fuse right? Not sure what other fuses are there, rail fuses? Regulated supply Fuses?
     
  20. avionic

    avionic " Black Knights " Subscriber

    Messages:
    41,563
    Location:
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    The BA has a "softstart circuit doesn't it ? You may have and shorted output transistor. Check the present resistance of those ballast resistors . R01* and R02* they may look like that cement block resistor close to the fuse in your photo. According to the manual 39Ω 7 watt.


    Edited.. My bad.. I was looking at the 3000. For the 5000 the ballast resistors are
    R733 and 734 3.9Ω @ 10 watt
     
    Last edited: May 3, 2018

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