recapping sx-850 for my son

Discussion in 'Pioneer Audio' started by nackesww, Mar 22, 2018.

  1. rcs16

    rcs16 Super Member

    Messages:
    3,389
    Location:
    Baldwin, Ontario, Canada
    Congrats, long struggle, but good outcome & experience to share with others attempting this journey.
    If the tuner is working fine, I'd leave it. It is a bit of a PITA to take apart with the dial string. Certainly does not hurt to clean the front panel switches,also the de-emphasis switch in the back.
    With age the tuners can get scratchy noise as you tune them, so you eventually will have to clean the var cap contacts when that happens. In the mean time enjoy.
     
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  2. 1MEGΩ

    1MEGΩ Active Member

    Messages:
    100
    Location:
    Mamou, Louisiana
    Actually, it is very easy to recap the tuner board. I have done many. If your son plans to keep this great Receiver, then you surely want the radio to keep working too. So I do suggest it be done at some point in time. After all, it is at least 41 years old.
    Here is what I do.
    First, turn the tuning knob all the way to the higher frequency 108 Mhz end until it stops and then turn it back if necessary so the tuner shaft pulley set screw is on top so you can unscrew it. The tuning gang will now be almost fully open and almost at its stop point.
    Now, get some good (new) duct tape. Cut a strip at least 7 inches long. Now, use a fine tip magic marker and put a dot on each end of the tuning shaft and tuning pulley bushing where they meet. That will relocate it when you reassemble it. You will then tighten and loosen the set screw on the pulley a few times to make a good impression on the tuner shaft and then just loosen the tuner pulley set screw and carefully pull it off the tuner shaft while keeping the Dial string taut and carefully lower it to the side of the chassis and hold it against the chassis while always keeping the Dial string taut.. Now place the center of the strip of duct tape onto the side of the pulley and place each end of the duct tape to the side of the chassis. Now you can work on the tuner with ease. NOW DO NOT TURN THE TUNING KNOB UNTIL YOU FINISHED THE RECAP AND EVERYTHING IS BACK IN PLACE! This is also a good time to clean the tuning gang shaft contacts. I use electronics cleaner. Works very well for me. Just remember to put the tuning gang back in the position it was before you cleaned it. Take good clear pictures of all the wires and the pins they are connected to, then remove the wires on the rear side of the tuner board so it can be flipped over toward the front of the receiver to remove and replace each capacitor. After you are finished with the recap, put the tuner board back in place, reattach the wires and place the pulley back onto the tuning shaft and align the marks you put earlier and set screw just touching the shaft and while holding the tuning gang with you index finger and turning the tuning knob back and forth just a little and moving the pulley left to right a few times, you can feel the set screw fall into the impression. Now tighten it just slightly snug and scan the dial to see if it is ok and the dial needle is on the right frequency (station) then tighten it good and you are done. It can be a little tricky to get the set screw just right when doing this your first time, but you will be able to tell when it is by the feel of it because you will now be able to turn the set screw about another half turn clockwise into the impression. And no need to recalibrate the dial if you do it correctly. Unless of course it was out of cal to begin with. Any questions, just let me know.
     
    Last edited: Apr 13, 2018 at 1:07 PM
  3. nackesww

    nackesww Member

    Messages:
    93
    Location:
    New Auburn, Wisconsin
    OK 1MEGO I'm going to go ahead with the tuner board. I spent a lot of time picking out the parts to put my order in with Mouser. Here is a list of what I came up with. Let me know if there is anything else I should put on the order.Many of the parts I have from previous orders.

    C25 4.7, 16V CEA 4R7P 16---4.7,35V,UPW1V4R7MDD
    C27 10,16V, CEA 100P 16---10,50V, UKL1H100KDDANA
    C28 0.47,50V, CEA R47P 50---0.47, 63V, B32520C1474J000
    C32 1,50V, CEA 010P 50---1,50V, UKL1H010KDDANA
    C34 47,16V, CEA 470P 16---47,35V, UPW1V470MED
    C35 100,16V, CEA 101P 16---100,35V, UPW1V101MPD
    C36 10,16V, CEA 100P 16---10,50V, UKL1H100KDDANA
    C37 10,16V, CEA 100P 16---10,50V, UKL1H100KDDANA
    C38 10,16V, CEA 100P 16---10,50V, UKL1H100KDDANA
    C39 0.22,25V, CSSA R22M 25---0.22,63V F612JF224J063A
    C40 1.5,25V, CSZA 1R5M 25---1.5,35V UMF1V1R5MDD
    C41 3.3,25V, CSZA 3R3M 25---3.3,50V, UKL1H3R3KDDANA
    C45 1.5,25V, CSZA 1R5M 25---1.5,35V UMF1V1R5MDD
    C46 1.5,25V, CSZA 1R5M 25---1.5,35V UMF1V1R5MDD
    C47 4.7,16V, CEA 4R7P 16---4.7,35V,UPW1V4R7MDD
    C48 0.1,25V, CSSA 0R1M,25---0.1,63V, BFC241641004
    C49 100,16V, CEA 101P 16---100,35V, UPW1V101MPD
    C57 47,16V, CEA 470P 16---47,35V, UPW1V470MED
    C60 4.7,16V, CEA 4R7P 16---4.7,35V,UPW1V4R7MDD
    C61 47,16V, CEA 470P 16---47,35V, UPW1V470MED
    C62 0.1,25V, CSSA 0R1M 25---0.1,63V, BFC241641004
    C65 220,16V, CEA 221P 16---220,35V, UPW1V221MPD6



    Transistors


    Q2 2SC535-B---KSD5041QTA ???
    Q3 2SC535-B---KSD5041QTA ???
    Q4 2SC461-B---KSC2383
    Q7 2SC945A-Q---KSC2383
    Q8 2SA733-Q---KSA992
    Q9 2SA733-Q---KSA992
    Q10 2SC1312-G---KSC1845
     
  4. rcs16

    rcs16 Super Member

    Messages:
    3,389
    Location:
    Baldwin, Ontario, Canada
    Hell bent on doing that tuner, okay,
    leave Q2,3,4 as is, they are RF bjts, your subs are no good.
    2sc945=512-KSC945CYTA
    2sa733=512-KSA733CYTA
    2sc1312=512-KSC1845FTA
    films, make sure they are 5mm lead centers, forget the PP types (BFC241641004), they are to big, use for speakers.
    Wima MKS2 & MPK2 series are a good choices
     
    Last edited: Apr 14, 2018 at 12:11 PM
  5. nackesww

    nackesww Member

    Messages:
    93
    Location:
    New Auburn, Wisconsin
    Last edited: Apr 14, 2018 at 2:30 PM
  6. rcs16

    rcs16 Super Member

    Messages:
    3,389
    Location:
    Baldwin, Ontario, Canada
    You could have used those others, except the RF ones. If you have the other ones on hand, I'd use them rather than another Mouser order.
    All those Wima MKS2 in 5mm lead spacings are fine to replace a ecap. Choose a 10% over a 20% tol. It does help to size up the original vs the replacement for fit/form as a basic check.
    I try to use up to 10uF film if I can vs a ecap but they are more expensive. I am sure the Pioneer EE would have wanted to use films too, if the management let him :)
     
  7. 1MEGΩ

    1MEGΩ Active Member

    Messages:
    100
    Location:
    Mamou, Louisiana
    As for the transistors, if your FM is working I would not replace ANY of the transistors, ESPECIALLY the RF Transistors. If it isn't broken then don't fix it!
     
    Last edited: Apr 15, 2018 at 9:10 AM
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  8. nackesww

    nackesww Member

    Messages:
    93
    Location:
    New Auburn, Wisconsin
    I placed my order.
     
  9. 1MEGΩ

    1MEGΩ Active Member

    Messages:
    100
    Location:
    Mamou, Louisiana
    One thing you need to know. Try to keep movement of the tuner board to a minimum as you replace the caps. Raising and lowering it will eventually cause the wires on the side of the board facing the front of the receiver to break off from the pins. Try to remove and replace the caps with the board on its edge as much as possible.

    Putting the pulley back on the tuning shaft:

    VERY IMPORTANT: Always keep the string taut so it can't come off the pulley.

    When you finish the cap replacement and you put the tuner board back in place, and you attempt to put the tuning pulley back onto the tuner shaft, you will see that now the center bushing of the tuning pulley can't reach the tuning shaft. That's because there is a spring on the inner side of the pulley and when you removed the pulley, the spring collapsed and pulled the string with it causing the whole thing to become shorter. What you have to do now, after CAREFULLY removing the pulley from the chassis, keeping the string taut, and keeping the pulley parallel to the chassis, is grab the rear panel of the receiver with your left hand and with your right hand begin putting a little pressure on the pulley in the direction of the shaft and at the very same time, rock the pulley clockwise and counter clockwise in a somewhat rapid manner. As you rock it back and forth 3 or 4 times, the spring will stretch out again along with the dial string and you will notice the center bushing will now reach the shaft and you can slip it right back on to the shaft. Realign the pulley on the marks you made and make sure the set screw is where it should be and lock it down. But remember, ALWAYS keep some pressure on the pulley to keep the string from coming off. You could put a couple strips of scotch tape across the pulley, but know that this could make it harder for the string to slip on the pulley as you rock it back and forth. Do this only if you have to. DO NOT put too much force on the pulley while doing this and keep the pulley parallel to the chassis at ALL times.
    Any questions please let me know.
     
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