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Audio Marantz PM500

Discussion in 'Troubleshooting and Repair' started by eytonbranhan, Nov 17, 2019.

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  1. Martaine2005

    Martaine2005

    2,575
    696
    May 12, 2015
    ESR/component testers on Ebay for £4.00. I bought one months ago to test it. It actually works pretty well.
    I don’t use it often as I have an ESR meter. Might be worth buying one on this occasion.

    Have you checked if there is DC on the amp speaker outputs?. It should be minimal in the millivolts if any at all.

    Sorry, just chiming in.

    Martin
     
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  2. Tha fios agaibh

    Tha fios agaibh

    2,083
    694
    Aug 11, 2014
    I doubt there's any dc comming out of the amp because everything works perfectly when the equalizer defeat button is pressed, which bypasses the Pf00 equalizer board.
     
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  3. Tha fios agaibh

    Tha fios agaibh

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    Aug 11, 2014
    I think this is a mistake on the print. Jf01 should be connected to Jh02 not grounded Jh05
    Screenshot_2019-11-24-11-28-59-1.png
     
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  4. Tha fios agaibh

    Tha fios agaibh

    2,083
    694
    Aug 11, 2014
    Caps around Qf01 and Qf02. Electrolytics for sure, but it's possible others are bad too.

    You've swapped components in this area from Qf01 side to Qf02 side and the problem didn't move to the opposite channel, so its possibile that a bad cap moved over but still caused an imbalance.

    I wish I knew more about the role of opamp pin 5 plays on this.

    I would love to hear from more knowledgeable members on the matter.
     
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  5. Martaine2005

    Martaine2005

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    May 12, 2015
    Could be a mis-print, can’t see the schematic atm.
    Either way, it once worked. You seem to have narrowed it down to the EQ board. So, all works except a ‘fader’ distorts the audio?.
    This happens on the LEFT channel only?.
    I read earlier about a ‘hiss’ noise. Was it hiss or hum?.
    And this noise is only audible when the EQ is turned on?.

    I would check ‘fader’ resistances and cleanliness. Spray with switch cleaner/deoxit depending on what side of the pond..(some countries drive on the wrong side!).
    Also, I would check solder joints.
    With amp switched on and no input signals. Just speakers, put a little pressure on the board. Probe around, carefully of course. A magnifier may be useful here. Some non- electrolytics might have cracks.
    But as this amp is late 1970s to early 1980s, it is due for a complete electrolytic replacement. Small ones included due to drying out.

    Martin
     
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  6. bertus

    bertus

    346
    112
    Nov 8, 2019
    Hello,

    @Tha fios agaibh < I found some more info on the QF01 and QF02 chips.
    They are the Toshiba HA1457.

    ha1457w.png

    Bertus
     

    Attached Files:

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  7. eytonbranhan

    eytonbranhan

    53
    10
    Oct 12, 2019
    I finally find the f***in' cause, these g***amn black wires :

    20191124_185135.jpg

    There were between PF00 and PF01, I finally noticed that some were oxidized and some were half-cut.

    So I changed them :

    20191124_185141.jpg

    No more weird sounds, pink, white or brown noise !

    Thank you all for your help !
     
    Last edited: Nov 24, 2019
  8. eytonbranhan

    eytonbranhan

    53
    10
    Oct 12, 2019
    yes you're right, I am waiting for a good caps kit for this amp, can't wait to receive it !

    Can be useful for the future, thank you I will save the datasheet !

    @Tha fios agaibh : a very special thank you very much for your support ;)
     
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  9. Tha fios agaibh

    Tha fios agaibh

    2,083
    694
    Aug 11, 2014
    That's great, good job!
    I'm curious which exact wires had a bad connection? Jf01, Jf02 inputs?

    Success is sweet isn't it.
     
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  10. eytonbranhan

    eytonbranhan

    53
    10
    Oct 12, 2019
    thank you !
    WF01 and WF02, the wires that are between PF00 and PF01, not JF01 and JF02.

    WF01.PNG

    yes absolutely ! :)
     
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  11. Tha fios agaibh

    Tha fios agaibh

    2,083
    694
    Aug 11, 2014
    Ahh, the input to Qf01 and 2 were essentialy untethered causing runaway gain.

    Thank you, I now have closure.:)

    Happy listening.
     
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  12. eytonbranhan

    eytonbranhan

    53
    10
    Oct 12, 2019
    you're welcome !

    I love so much the sound of this amp ! so happy to retrieve it ! thanks again for the support !
     
    Tha fios agaibh likes this.
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