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UREI 6500 issues

Discussion in 'Solid State' started by hamrules, Nov 3, 2018.

  1. hamrules

    hamrules Member

    Messages:
    74
    Location:
    Milwaukeee Area
    I got this amp and I replaced a few resistors that were wrong from someone else so both boards are correct and identical and the caps on the control boards too. One control board after turning on lights up the normal led and the clip led stays on and the output relay closes. It does this for either amp module it’s hooked to. The other control board after turning on lights up the normal led, the clip led goes off and the relay closes. Then after 30 seconds the relay starts to open and close constantly along with the clip led lighting up and off. It does this for either amp module it’s hooked to. I’m not sure what to look for to figure this out. Should I check all the output devices to see if any show bad, there’s 14 per module. The only thing I have is the circuit drawing from the JBL site.
     

     

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  2. avionic

    avionic " Black Knights " Subscriber

    Messages:
    43,684
    Location:
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    A link would be handy.
     
  3. hamrules

    hamrules Member

    Messages:
    74
    Location:
    Milwaukeee Area
    Here's the link to the file: jblproservice.com/pdf/Vintage JBL-UREI Electronics/UREI-6500.pdf
     
  4. avionic

    avionic " Black Knights " Subscriber

    Messages:
    43,684
    Location:
    Fort Dodge, Iowa
    Does this channel work?
     
  5. avionic

    avionic " Black Knights " Subscriber

    Messages:
    43,684
    Location:
    Fort Dodge, Iowa
    Was this amp working or non-working before you started?
     
  6. hamrules

    hamrules Member

    Messages:
    74
    Location:
    Milwaukeee Area
    I have not hooked it up to a speaker but it does show 12.8mv DC offset at the speaker terminal.
     

     

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  7. hamrules

    hamrules Member

    Messages:
    74
    Location:
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    I bought it and they said it was working but i'm doubtful it really was. I did not actually try it first, maybe I should have.
     
  8. avionic

    avionic " Black Knights " Subscriber

    Messages:
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    Location:
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    Thats hardly any DC offset.:thumbsup:
     
  9. hamrules

    hamrules Member

    Messages:
    74
    Location:
    Milwaukeee Area
    If I move the control board to the other amp channel then it does this identical thing and has 13.0mv DC offset at the speaker terminal.
     
  10. avionic

    avionic " Black Knights " Subscriber

    Messages:
    43,684
    Location:
    Fort Dodge, Iowa
    Can you post photos of the parts you replaced on the channel that the relay toggles on and off ?
     
  11. hamrules

    hamrules Member

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    74
    Location:
    Milwaukeee Area
    I will shoot some pics and get them up later on.
     

     

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  12. avionic

    avionic " Black Knights " Subscriber

    Messages:
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    Location:
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    Guess that narrows it down to the control board.
     
  13. hamrules

    hamrules Member

    Messages:
    74
    Location:
    Milwaukeee Area
    20181103_223032243_iOS.jpg 20181103_223040817_iOS.jpg 20181103_223044838_iOS.jpg

    1st is an amp board
    2nd is a control board
    3rd is the other control board
    I didn't take a pic of the other amp board

    I was checking the resistors and there seems to be a huge variance in readings on what some of them should be and from control board to control board for the same one on some of them. I'm thinking maybe that's the issue.
     
  14. avionic

    avionic " Black Knights " Subscriber

    Messages:
    43,684
    Location:
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    Compare voltages on IC1 pin 14 on both channels.
     
  15. hamrules

    hamrules Member

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    Location:
    Milwaukeee Area
    OK. I can see why, now that you said that. I will have to figure out how though as there is no access once they are plugged into the case. No bottom that opens at all.
     
  16. avionic

    avionic " Black Knights " Subscriber

    Messages:
    43,684
    Location:
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    Tack a test wire to the pins on the solder side.
     

     

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  17. avionic

    avionic " Black Knights " Subscriber

    Messages:
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    IC1 is one of those two socketed chips. Should be accessible from the top side. Just be extremely careful not to short out adjacent pins with your test probe.
     
  18. avionic

    avionic " Black Knights " Subscriber

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    43,684
    Location:
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    [​IMG] TL084CN
     
    Last edited: Nov 3, 2018
  19. avionic

    avionic " Black Knights " Subscriber

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    Location:
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    What part number is printed on those chips?
     
  20. avionic

    avionic " Black Knights " Subscriber

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    43,684
    Location:
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    Put a piece of heat-shrink tubing or electrical tape over the probe tip. Leaving just the very point exposed.
     

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