Marantz 4400 voltage for FM board

Discussion in 'Marantz Audio' started by daveyh, Aug 21, 2017.

  1. daveyh

    daveyh AK Subscriber Subscriber

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    Does anyone know what drives the voltage on the FM board for the Marantz 4400? Is there a special board? I rebuilt the power supply and I get stations in FM but not like it should in FM stereo. Some channels are strong and some weak. No stereo lamp and I do not think I am getting stereo in FM.
     
  2. petehall347

    petehall347 the brandy coffee man

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    follow the wires from power supply board to tuner boards . most likely end up at the largest cap on the tuner board .
    this manual i have must be same as yours . no schematics.
     
  3. daveyh

    daveyh AK Subscriber Subscriber

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    Thanks Pete. If I change out the caps in the board will I have to have it aligned? I don't have the equipment and don't know how.
     
  4. daveyh

    daveyh AK Subscriber Subscriber

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    I see my subscriber membership has expired but I have my payment ready to send!
     
  5. petehall347

    petehall347 the brandy coffee man

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    just change power caps . alignment is another story . i try to believe if it hasn't been touched from new .then new caps shouldn't change much so long as you leave the ceramic ones as they are .
    radio stuff in not really my thing .
     
  6. txturbo

    txturbo AK Subscriber Subscriber

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    The 4400 MPX board is not easy to recap.. I am working on one now and it's no fun.

    The first thing I would recommend is cleaning the tuning capacitor. If some stations are good and others not this could be the problem. Check the tuner forum for a link on how to clean it.
     
  7. tranguru

    tranguru Active Member

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    Hi

    sounds very similar to what I had on my 4400 a few months ago.

    I would leave the tuning cap alone for the moment, unless you see a lot of dust in it.

    recapping is a lot of work indeed - see my post on the subject. but not sure it changed that much actually

    check the voltages on the IC directly.

    what helped me get the stereo decoding on again what the adjustment of the discriminator coil - see my post of the topic
    I only learned about this after I had recapped ....:(

    recapping won't affect alignment
     
  8. daveyh

    daveyh AK Subscriber Subscriber

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    I tried cleaning the tuning capacitor already. No change. Used a dry pint brush and then tried CRC non-residue QD spray. No change.
     
  9. daveyh

    daveyh AK Subscriber Subscriber

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    Where is your posts on what you done. I don't see a link???
     
  10. daveyh

    daveyh AK Subscriber Subscriber

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    I think I have a guy who said will look at it for me but he does old radios and not really up on stereo FM. He works on old Ham radios. I think he can do it. He's pretty sharp.
     
  11. petehall347

    petehall347 the brandy coffee man

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    he will for sure know more than me . i have played with fm many years ago and moving the simplest things can have an effect . like innocent looking coils and such . prob just needs a simple tweaking .
     
  12. tranguru

    tranguru Active Member

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  13. daveyh

    daveyh AK Subscriber Subscriber

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  14. txturbo

    txturbo AK Subscriber Subscriber

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    That's not really how it should be done.. Take a look at this

    What your really trying to do is clean any corrosion off of the contacts between the shaft of the tuning capacitor and the frame that holds it. The symptoms that you describe with only some parts of the dial working normally from a signal strength perspective can be caused by this. The stereo beacon can be something else..

    Oh... I am in the process of reaping the MPX board. The wires were removed from the board and marked, the entire board was removed. Then the board was re-caped on the bench. Small wire extensions with matching colors were made. The connections are being made to the posts by soldering a PCB test point to the end of the extension wires and then sliding it over the post and soldering it down. In the future if the board needs to be removed is can be by simply heating up the solder and slipping the wire off. More pictures soon.. (Thanks Mitch)

    [​IMG]


    [​IMG]
     
    daveyh and MBuras like this.
  15. tranguru

    tranguru Active Member

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    nice work on the board

    I tried another approach (putting new connectors) - was a very bad idea...
     
  16. daveyh

    daveyh AK Subscriber Subscriber

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    I also cleaned the shaft with 100% Deoxit. Not the fins! Just the brass shaft after I spray it with CRC Quick Dry Electronic Cleaner. I just did not mention it in my post.
     
    Last edited: Aug 27, 2017
    txturbo likes this.
  17. Halisson

    Halisson New Member

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    I went through the same problem on a 4400 never tweaked. I had to adjust the MPX separation if I'm not mistaken, many years ago and I never made the adjustment again. carefully and adjust using an oscilloscope.
     
  18. daveyh

    daveyh AK Subscriber Subscriber

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    Haven't had a chance to take this to a friend of mine yet. He's going to help me align it. He has all the equipment. Hopefully we can get this fixed. Thanks!
     
  19. daveyh

    daveyh AK Subscriber Subscriber

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  20. txturbo

    txturbo AK Subscriber Subscriber

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    I used a label maker ( I think it's made by Brady or Dynamo) with a wire marker setting and trimmed the excess off.

    The test point makes the reinstallation simple. Just slip the wires onto the posts, tack them down and your done.

    [​IMG]



    [​IMG]
     
    Last edited: Sep 7, 2017

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