Pioneer M-22 Repair/Restoration

Discussion in 'Pioneer Audio' started by kunsang, Feb 15, 2016.

  1. kunsang

    kunsang New Member

    Messages:
    4
    I was quite lucky and got an M-22 in good condition for free. Sadly only the right channel was working and after some testing, the other channel stopped working aswell.
    The replacement caps I ordered (Nichicon KZ, FG and VX) have arrived today and I'm about to start recapping.
    The output transistors seem to be fine but I didn't check each of them individually.
    The images are of the left channel PCB which is a bit bent. I already removed one leaking axial cap.
    Is there anything else to watch out for / replace?

    _DSC4499.jpg Full Resolution
    _DSC4500.jpg Full Resolution
    _DSC4506.jpg
     

     

    Please register to disable this ad.

  2. EchoWars

    EchoWars Hiding in Honduras

    Messages:
    28,407
    Location:
    Kansas City
    I'd be using 105°C caps everywhere, including the axial caps. There are a grand total of two (2) caps in the signal path, and those are nice 3.3uf film caps, so there's no need for so-called 'audio' capacitors...they just aren't up to the job as far as temperature is concerned. The caps should be chosen for their longevity first, which means Panasonic FM or FC, or Nichicon PW or HE.

    As far as the axial caps, Digikey sells some from Vishay/BC Components that will last decades.
    1000uf 63V - 4249PHBK-ND
    470uf 63V - 4247PHBK-ND

    That 22uf 160V non-polar electrolytic is a PITA. I believe the last M22 I restored, I used an inexpensive metallized film cap here...something designed for a speaker crossover. Pretty sure I used this one: http://www.parts-express.com/dayton-audio-dmpc-20-20uf-250v-polypropylene-capacitor--027-436
     
    Last edited: Feb 15, 2016
    slimecity likes this.
  3. kunsang

    kunsang New Member

    Messages:
    4
    Oh ok, thanks I didn't know that.
    I have a full set of audio-grade Nichicons, and I have already replaced the big ones on the left PCB.

    So you suggest I should get more durable capacitors and ditch the Nichicons?
     
  4. kunsang

    kunsang New Member

    Messages:
    4
    Last edited: Feb 15, 2016
  5. EchoWars

    EchoWars Hiding in Honduras

    Messages:
    28,407
    Location:
    Kansas City
    If you've run the amp for any length of time, you see how hot it runs. I'd be putting in the longest-lasting high-temp caps I could, like those in my first post. I'd also want nice 25-turn Bourns sealed trimpots for bias and offset adjust.

    That Illinois Cap would be fine.
     
  6. kunsang

    kunsang New Member

    Messages:
    4

     

    Please register to disable this ad.

  7. gvocale

    gvocale New Member

    Messages:
    45
    Location:
    New York
    Hi, I am just restoring an M22 as well. See the photo of my input boards before restoration.

    Does those large diodes on the left side of the top board look original to you, or replaced? Seem pretty large, probably they've been replaced before.

    Do I need to replace any diode / trimmer / relay or else?

    IMG_7244.JPG
     
  8. omri617

    omri617 Super Member

    Messages:
    1,155
    Location:
    Israel
    Good luck with your work! I really love the M-22 even though never saw or listened to .
    Which makes me think - how does the M-22 sound comparing to TOTL pioneer receivers / integrated amps?
     
  9. slimecity

    slimecity Super Member

    Messages:
    2,786
    Location:
    New Zealand
    To the OP - Second the high temp cap replacement advice. Replacing the trimmers is also essential.

    I would do is clean all the molex pins and sockets- these can get dirty. Then put the unit on a DBT with a (say) 150W bulb, then check your DC offset and bias. A loose connection could be preventing power getting to where it should be. You want to be very careful with this amp as the bias runs high.

    With the exception of doing the stuff EW recommends above, You want to diagnose why channels arent working generally before doing a fullscale recapping etc.

    Interesting to see a couple of M22 posts on here at the same time. These are phenonemal sounding amplifiers once working properly.
     
  10. gvocale

    gvocale New Member

    Messages:
    45
    Location:
    New York
    slimecity likes this.
  11. gvocale

    gvocale New Member

    Messages:
    45
    Location:
    New York

     

    Please register to disable this ad.

  12. omri617

    omri617 Super Member

    Messages:
    1,155
    Location:
    Israel
    Are the diameters the same?
     
  13. gvocale

    gvocale New Member

    Messages:
    45
    Location:
    New York
  14. darkhawk22

    darkhawk22 New Member

    Messages:
    30
    Location:
    Acworth, GA
    Good luck on your M-22 restorations. Having restored one myself I can say they are excellent sounding units once restored and the offset is closely matched. I did not replace the larger 33000uf caps just the other internal ones along with the power supply board diodes and metal film capacitors (high heat area).
     
  15. mshari

    mshari New Member

    Messages:
    2
    Hello
    My little experience in electronics
    I have a pioneer amp M22 there is high heat of displacement 850-vr1 vr2 What is the way to adjust it
    Thank you
     
  16. slimecity

    slimecity Super Member

    Messages:
    2,786
    Location:
    New Zealand
    If the amp adjustments are correct and both channels are putting out the same relative "heat" (based on a rough subjective assessment) then chances are your M22 is running fine.

    You cant adjust temp on the M22 - you can adjust the speaker offset and bias. This is a class A amp - its supposed to run hot.

    Dont attempt to make these adjustments unless you know what you are doing.
     

     

    Please register to disable this ad.

Share This Page