2220B Troubleshooting

Discussion in 'Marantz Audio' started by mvh363, Jul 10, 2018.

  1. mvh363

    mvh363 New Member

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    I have recently purchased a Marantz 2220B as-is, fully expecting it wouldn’t be fully operational. I’ve done some basic service on amplifiers before so I figured it wouldn’t be too difficult a task to try and get this one going, but my limited knowledge and experience has unfortunately left me stumped on the most significant issue.

    I cleaned it up so I could visually inspect for any obvious component failures, hooked up some sacrificial speakers, and powered it up. I found the right channel operates as-expected, but the left channel produces a loud crackling that is completely unaffected by the controls - changing the input, or adjusting the volume and balance does nothing to affect this noise, but the audio underneath is still present. Since it’s only affecting one channel, it seems logical that the fault isn’t in the power supply, and as it’s unaffected by controls, led me to believe the fault is in the power amplifier.

    Initially, I thought it might be an issue with the output transistors, but I pulled and tested them with a multimeter and they seemed fine. I then checked the bias on the outputs using the locations posted in the service manual correction thread, and both channels were out of spec, with the left moreso. I adjusted the right, but the left channel wasn't giving me solid readings while trying to dial it in, so I’ve put that off for now assuming that the bias issue in that channel are largely another symptom of the primary fault I've yet to ascertain.

    Any ideas what I should be focusing on at this point? I thought it may be an issue of bad capacitors due to the unit's age, so I ordered the requisite components for a recap, but I don’t know if they would cause this sort of issue without any immediately noticeable signs of failure on the main amplifier board.
     

     

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  2. Jailtime

    Jailtime Standin' on a corner Subscriber

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    Seems to me like you have narrowed it down pretty well. Take a look at the differential pair transistors, H701 thru 704. Gain match them in pairs with a multimeter that has hFE function. KSA992 would be a good replacement for them.
     
  3. ChrisMarantz

    ChrisMarantz AK Subscriber Subscriber

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    Don't discount the age of the Receiver. I rebuilt a Marantz 1060 recently with the same sort of symptoms - replacing the capacitors on the amplifier board solve the problem - Chris
     
  4. buttahman

    buttahman Active Member

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  5. mvh363

    mvh363 New Member

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    Thanks for the help everyone, I really appreciate it and my amplifier is coming together nicely.

    Now I need to handle the other minor issues, but I think I've got those figured out. There's a handful of bad caps on the MPX board which explains the lack of Stereo over FM, but the signal meter is stuck and doesn't seem to work on AM either and I don't know if the MPX board would have anything to do with that, or if the meter is simply shot. I'll also have to replace/upgrade the fuse lamps since half of them are out, but that should be relatively easy in comparison.
    I was waiting for the transistors to come in before I bothered to recap the power amplifier because it's less than accessible. I swapped the differential pairs with matching sets while changing out the caps and now it's dead silent at idle, so thanks for the tip.
    The leads on the transistors didn't look so great after I got a better look at them, so they were probably the issue.
    Who would have thought that the freebie multimeter from Harbor Freight would have be the MVP for this project? I'm surprised it was the only meter I had with an hFE function.
     
    Jailtime likes this.

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