Pioneer M-73 power amp

Discussion in 'Pioneer Audio' started by animefreeks, Apr 4, 2016.

  1. animefreeks

    animefreeks New Member

    Messages:
    45
    Hello AK

    old pioneer M-73 power amplifier to resurrect from storage.

    Does anyone have a schematic Diagram / service manual for the Pioneer M-73? the one I always get is the M-73 model for the 90's. I have the silver plated M-73 from the 70's-80's (I think).

    Also any recommended check points for the pioneer m-73 (voltage, test pins, overall checking if its in good condition)?

    I have tried to power on the amp (without any source on it, no speakers connected), I hear one click on the relay, a few busted lights and a bent power switch.


    Thank you in advice
     

     

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  2. smurfer77

    smurfer77 AK Subscriber Subscriber

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    Not familiar with this amp but did find the service manual over on hifiengine
     
  3. animefreeks

    animefreeks New Member

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    Hello smurfer77

    Thanks for the link, this is the 90's version of the M-73, mine is a silver face plate similar to a spec models.

    thank you
     
  4. smurfer77

    smurfer77 AK Subscriber Subscriber

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    Ahh. And now i read your first post more carefully. If you find it pls upload it :)
     
  5. larryderouin

    larryderouin Turn it UP, POP? PLLUUEEEZZZZZEE Subscriber

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    Easiest way to tell age is to use the date coding in the Sticky thread called PIONEER DATES of MANUFACTURE. It tells you how to use your serial # to figure what month and year your gear was made.

    Also google PIONEER M-73 and look for the AUDIOKARMA group of links.
     
  6. QSilver

    QSilver Super Member

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  7. animefreeks

    animefreeks New Member

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    Hello QSilver

    Yes this is the one I have, the Schematic I always get is the m-73 from the 90's. I am looking for the schematic / service manual for that pioneer M-73 :D


    Hello larryderouin
    Will post the Serial number soon


    Thank you
     
  8. QSilver

    QSilver Super Member

    Messages:
    1,206
    That is a Japan only model according to Rick's Steremanuals site. It says this is very close to the SPEC-4 so you might be able to use the SPEC-4 manual and schematics to get it going. Can you post a picture? The M-73 looks be 85wpc whereas the spec-4 is 150wpc. My initial thought is that the PSU voltages might be different but maybe your schematic will show that. Can you show us the schematic you have?

    I was looking http://www.stereomanuals.com/man/rep/pioneer/pioneer_manuals_m.htm here for info
     
  9. animefreeks

    animefreeks New Member

    Messages:
    45
    Hello QSilver

    Images attached for Pioneer M-73 power amp, also include the image with serial number, SM i have is for a re-used model M-73 90's version.


    Thank you
     

    Attached Files:

  10. QSilver

    QSilver Super Member

    Messages:
    1,206
    Wow that looks very like a SPEC 4 inside... except a bit smaller :biggrin:

    I would imagine though, that some things will have changed.... I think it would be wise to contact Rick at stereomanuals and ask him about the spec-4 service manual and what the differences are compared to yours. Can you get a close up shot of one of the power amp boards? It might help to identify some of the transistors etc.

    The serial number dates it to January 1977.
     
  11. smurfer77

    smurfer77 AK Subscriber Subscriber

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    210 W power consumption noted on the third image seems a tad under what I would except.
     

     

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  12. QSilver

    QSilver Super Member

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    85+85W output? It does say "effective output"... Though the VUs do seem to show 100W at 0dB....
     
  13. animefreeks

    animefreeks New Member

    Messages:
    45
    Hello

    Funny thing just happened i got the C-73 pre-amp for my m-73 power amp, I tried it and it was working properly i was amaze, I cleaned it up both pre-amp and power amp some minor issues on my c-73 broken plastic thing connecting the source selector, but a glue and some lace did the trick, my problem now is the power amp, it does power on but the relay is not clicking any more, what i did was spray some cleaner on the meter board and on the output board and tap on the relay.

    now it only power up and i can see the left meter drifting and no relay click. :(:(:(:(:(

    Any one have an idea where to check??
    thank you
     
    Last edited: Jun 26, 2018
  14. animefreeks

    animefreeks New Member

    Messages:
    45
    Hello AK
    Requesting your assistance once again


    My M73 power amp in protection mode Checking the DC offset of the left channel is quite High 100+ mV and Right channel is around 30mV

    I have checked the voltage on the pins chassis ground to pins ANP-548-B board
    1. 0.6v
    2. 60.5v
    3. 0v
    4. 0.6v
    5. 60.5v
    6. 0v
    7. -0.4v
    8. -60.3v
    9. 0v
    10. -0.4v
    11. -60.3v
    12. 0

    I compare them with the right channel values are almost the same there's a slight difference of 0.3~0.6 volts


    also checked the voltage value of on the meter boar, I can not seem to fine the model number on the meter board but there are 33 pins total ill provide the pins with values some of the pins have 0 volts
    1. 0.2v
    5. - 15.8v
    6. 0.1v
    7. 0.1v
    8. 77.1v
    9. 77v
    11. - 48.6v
    13. 49.5v
    14. 49.5v
    15. 16.1v
    16. 0.1v
    21. 60.8
    22. - 48.7v
    28.. 49.5v
    30. 0.4v
    31. 0.4v
    32. 16.1v
    33. - 16v

    if anyone can provide some insights would gladly apricate it.


    Thank you
     
  15. animefreeks

    animefreeks New Member

    Messages:
    45
    Hello AK member

    Does anyone have a Pioneer M 73 to compare voltages with?? I tried to us the SPEC 4 as reference and it made me more confuse, Pin numbers are different, VR pots are different, layout is different.

    Thank you for your assistance
     
  16. Gino_Gino

    Gino_Gino New Member

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    2
    Location:
    Snowy Russia
    Hi animefreeks,

    I have this sweety pair. With cracles in channel. Once I already repaired it. That time guilty was 2SA798. (I replaced in both channnels although only left channel had cracles).

    Now cracles came back. Hope to repair it some day once again. Looking for replacement for all TO-126 transistors...

    M-73 definitely is not a domestic version of SPEC 4 as many people thinking.

    Meter board: AWM 107A (SPEC 4 - AWM 113)
    Power Amplifier board: AWH 052 (SPEC 4 - AWH 065)
    Power Supply board AWR 126 (SPEC 4 - AWR 139)
    Fuse board: AWR 125 (SPEC 4 - AWR 143
    Electrolytics: 12,000 x 63V (SPEC 4 - 22,000 x 80V)
    Trasformers: ATT 385 / 386 (SPEC 4 - ATT 416 / 417)

    Pair of AWH 052 are being used for SA-8500II and SA-9500II models. They are described in appropriated Service Manuals.

    I did not find AWM 107A in any other Pioneer devices with similar external layout. The only SM-1800II has not been checked, because Service Manual for this model is not available for me.
     
    Last edited: Jul 23, 2018

     

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  17. animefreeks

    animefreeks New Member

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    Hello AK members

    Sorry to bother you all, If I may Request your assistance at your free time. If I can have a Image of your m 73 power amplifier output transistors layout? 2sb618a(b618a) and 2sd588a(d588a) for both channels if possible, my images failed me and I dis-assembled them T_T now not sure for the layout on which side the transistors goes on.


    Thank you very much for your assistance.
     
  18. inductor

    inductor Super Member

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    1,610
    Location:
    uk
    and the moral is take pictures before dismantling anything
     
  19. animefreeks

    animefreeks New Member

    Messages:
    45
    Hello inductor

    most proper moral lesson on my part is "Do not save images on your mobile phone and let the kids play with it, Copy it somewhere else ^_^ " T_T

    regards
     
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