1. Time for some upgrades in server hardware and software to enhance security and take AK to the next level. Please contribute what you can to sales@audiokarma.org at PayPal.com - Thanks from the AK Team
    Dismiss Notice

Sansui G-22000 Restoration/Upgrade Thread

Discussion in 'Exclusively Sansui' started by mattsd, Oct 28, 2018.

  1. bktheking

    bktheking Gitter Done! Subscriber

    Messages:
    12,864
    Location:
    Ottawa Ontario
    Nice, ya after I wrote you I was thinking relays, then i just changed the 2 on the right channel lol.
     
    kevzep likes this.

     

    Please register to disable this ad.

  2. mattsd

    mattsd AK Subscriber Subscriber

    Messages:
    1,632
    Location:
    Cincinnati, Ohio
    Here are the motherboards!

    Motherboard for Flat Amp Boards (F-2888)

    The motherboards are pretty simple, they hold the local decoupling caps along with the bypass caps for aforementioned caps.

    [​IMG]

    [​IMG]

    The local decoupling caps for the flat amp boards are C07 and C08, they are 470uF 35v. They were upgraded to Panasonic FM 680uF 50v caps. The decoupling bypass caps are .1uF mylar film and were replaced with same value Wima MKP10 polypropylenes. C901 is a 470uF 6.3v and was replaced with a 470uF 16v Panasonic FM.

    [​IMG]

    [​IMG]

    Motherboard for the EQ Amp Boards (F-2884)

    Very similar setup to the flat amp motherboard with the two decoupling caps and bypass caps, however this board has the rotary switches for the function and impedance selectors.

    [​IMG]

    The rotary switches for this unit were pretty heavily oxidized, so I went ahead and pulled them both and cleaned them with a ultrasonic cleaner.

    Before:

    [​IMG]

    [​IMG]

    And after! I wasn't able to get them perfectly shiny, but they look a lot better than before.

    [​IMG]

    [​IMG]

    Now for the impedance selector switch. Before:

    [​IMG]

    [​IMG]

    And after! Again, not perfectly shiny but much better than before.

    [​IMG]

    [​IMG]

    And the motherboard after! The decoupling caps C01 and C02 were 470uF 35v like the other board and were upgrade to 680uF 50v. The decoupling bypass caps (C03 and C04) are .1uF mylar film and were replaced with .1uF Wima MKP10.

    [​IMG]

    Up in the next post, the big power supply board!
     
    larry777, Hipocrates and Hyperion like this.
  3. kevzep

    kevzep Its all about the Music Subscriber

    Looking good Matt, this is where I am headed with my G22K, the good old rotary and lever switches...I suspect mine are heavily oxidised like that....
     
    Ronald.C likes this.
  4. txturbo

    txturbo AK Subscriber Subscriber

    Messages:
    922
    Location:
    Austin, TX
    Nice! I have one for another AK'er thats ready to get the treatment.

    :lurk::lurk::lurk:
     
  5. mattsd

    mattsd AK Subscriber Subscriber

    Messages:
    1,632
    Location:
    Cincinnati, Ohio
    Power Supply Board (F-2891)

    This board is the hardest one to get to out of all the boards in this unit and requires a considerable amount of disassembly to be able to access properly. The board itself is fairly easy to work on however.

    [​IMG]

    C03, C10, C11 and C17 are 1000uF 50v, replacements were 1000uF 50v Panasonic FM. Interestingly, C10 and C11 in the +34v regulator are 1000uF 50v, but only C03 (C10) in the -34v regulator is a 1000uF 50v. C04 (C11) was only a 470uF 50v, even though the setup is identical between the regulators. C04 was upgraded to a 1000uF 50v to match C03. The regulator transistors were replaced with KSB596 and KSD526. The caps shunting the zener diodes, C06, C13 and C21 are all 100uF 10v and were replaced with 100uF 25v Panasonic FM. C07 and C14 were 1uF 50v electrolytic and were replaced with 1uF 50v Wima film. C28 and C29 were 2.2uF 50v and were replaced the same value Nichicon PW. C18 was a 470uF 50v and its replacement was of the same value. C19 is a 220uF 35v and was replaced with a 220uF 50v. C22 was a 3.3uF 50v and was replaced with the same value. C27 was a 220uF 50v and was replaced with the same value. C30 was a 100uF 16v and was replaced with a 100uF 25v. C31 and C32 were 100uF 35v and were replaced with 100uF 50v. The zeners ZD01, 02 and 03 are all 6.2v 500mW and were replaced with Vishay 2% zeners. Relay replacement was a Omron MY4. 3 glue damaged metal oxide resistors were replaced, R01, 08 and 17, also replaced was R27, the 330 ohm 1/2w fuse resistor that is a common cause of the power meters not working in this unit. Replacement was a 1/2w metal oxide.

    [​IMG]

    Bonus, cleaning the pre-main switch. These switches are notorious for causing drop outs in one channel or the other, even after being cleaned with Deoxit. Only true way to make sure they don't cause trouble is to take them apart and clean the contacts manually.

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    Just two boards left in this preamp unit! Tuner board and the meter amp board, after that we will move on to the power amp section. Stay tuned!
     
    Hipocrates and Hyperion like this.
  6. kevzep

    kevzep Its all about the Music Subscriber

    How on earth did you get the separated/connected switch out? I am very impressed!!
     

     

    Please register to disable this ad.

  7. mattsd

    mattsd AK Subscriber Subscriber

    Messages:
    1,632
    Location:
    Cincinnati, Ohio
    Very carefully, it's a pain in the butt to get to, that's for sure. You first have to take off the big gray trim/frame piece and the black metal faceplate panel, then with the edge of a jewelers flat-blade work the 4 black push pins out that hold that board on. This is delicate work and it's not hard to damage or destroy them, thankfully I've had to remove several before on Sherwood and Pioneer receivers, so I've had practice. Even after those are all loose it doesn't have much slack to move, you have to create it. After that there just enough wiggle to turn the board to pull the switch out after you de-solder it. Funny enough taking apart the switch itself is the easiest part. One note though, be very sure you note exactly how it comes apart, you can put it together backwards.
     
    Hyperion likes this.
  8. Hyperion

    Hyperion Roobarb & Custard Subscriber

    Messages:
    48,106
    Location:
    Hertfordshire, UK
    Yeap, the overall procedure sounds familiar, although I have never worked on a G22K. :) I even have a stock of those black plastic 'push pin' fixings just in case I manage to damage one. :)
     
    Last edited: Nov 18, 2018 at 3:45 AM
  9. kevzep

    kevzep Its all about the Music Subscriber

    Thanks for the explanation, I will be doing this when my pre-amp comes out of service for a bit of maintenance...
    I figured it would not be easy.
     

Share This Page