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Philips 41JP20 RPTV

Discussion in 'Electronic Repair' started by James Sweet, Jan 30, 2004.

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  1. James Sweet

    James Sweet Guest

    Got this set dead, fuse was blown. Replaced the BUW12 on the power board,
    checked out the rest of that board and fired it up. Power light came on then
    set went dead, stupid me, I missed the separate HOT on the sweep board, it's
    shorted too. I plan on replacing these parts and trying it again, but first
    is there anything major that often fails on these sets? I'm hoping the
    flyback and HV block are good, it's a fairly old TV but looks to be in nice
    shape and has been sitting for several years.
     
  2. Bill Jr

    Bill Jr Guest

    James,
    Usually the H.O.T. short will take out that BUW12A.
    Mostly caused by poor solder connections everywhere.
    The H.O.T. can be replaced with a 2SD1710.
    Unless you have the original BU508v laying around.
    You will most likely have a coolant contamination situation when you get it
    running.
    Also, always replace the 100uf 200volt cap in the power supply.

    Good Luck,
    Bill Jr
     
  3. James Sweet

    James Sweet Guest

    I replaced the HOT with something I had in my scrap box that has similar
    specs, NTE lists the same replacement for both it and the BU508V so
    hopefully it'll work. Replaced the BUW12A with another similar transistor,
    should have ordered more than one of the correct part, but at least if that
    fries again it should only take out the fuse. The TV is out at my mom's
    place and the boards are here so I'll have to drive out there and see if it
    works. The ESR checked out ok on that cap, does it usually fail? I did find
    quite a few cracked solder joints, figured that's probably what caused the
    original failure.

    As for the coolant, I'll cross that bridge when I come to it, so far I've
    been lucky and never had to deal with contaminated coolant, first time for
    everything though I suppose.
     
  4. Bill Jr

    Bill Jr Guest

    James,
    I always replace that 100uf 200 volt cap just for general principle.
    They fail regularly.
    The transistors aren't that critical on specs so you should be ok.
    Not like a Sony.
    If you do need some assistance for coolant issues just holler.

    Good Luck,
    Bill Jr
     
  5. James Sweet

    James Sweet Guest

    Well apparently my sub in the PSU won't cut it, nothing fries but the supply
    doesn't come up either, relay clicks, there's a faint buzzing sound but none
    of the outputs come up. 12v standby is present and the power indicator does
    come on.

    I checked and the blue and green coolant is indeed contaminated, fortunatly
    the tubes themselves look to be in good condition, the phosphor is nice and
    white-ish with no burn that I noticed. MCM stocks the BUW12A's and coolant,
    how much do I need to redo all 3 tubes? I know this has been asked before
    but I never paid much attention since I've never had this problem. Before I
    place an order, are there any other parts I'm likely to need to complete
    this?
     
  6. Bill Jr

    Bill Jr Guest

    James,

    You might want to pull that Oscillator board that mounts to the deflection
    board and resolder the edge connector.
    There are 2 resistors in series that perform startup on the power supply
    board.
    Located near the center of the board. 330k and 300k if memory serves.
    These open up and cause a no start condition. While they are going open they
    cause power supply to go crazy. There is special zener diode (Z4 if memory
    serves) that can short.



    Also could be a bad flyback.

    Below is a snippet from a post made 4/24/2002 by me:
    For everyone's info....the flybacks listed below are for the most common NAP
    Projo sets as listed at MCM at that time. Pricing may vary accordingly.
    These are used in the APW009 thru APW028 and maybe a few more.

    NAP p/n MCM p/n HR Diemen p/n MCM pricing
    362135-1 33-3714 HR6480 $25.96
    362135-2 33-3716 HR6481 $25.96
    362140-1 33-4286 HR6493 $26.78
    362140-2 33-4288 HR6494 $26.65

    The following are used to replace the big white square block type flyback
    used in some alternate version APW009/010 and possibly APW007/008 boards.

    NAP p/n MCM p/n HR Diemen p/n MCM pricing
    362003-6 33-4296 HR6541 $34.81
    362003-7 33-4298 HR6542 $34.81


    As far as the coolant goes, I have only replaced coolant in the Red CRT
    chamber once in all my years of doing them. If it is clear then leave it
    alone. This will also serve as a reference when setting up the other CRT's
    after removing them and changing coolant.
    It should take about 9-12 ounces per tube to do coolant change. I would
    recommend 2 bottles of 16 ounce coolant to be sure to get the job done.
    As long as you are placing an order for parts go ahead and get the correct
    transistors.
    If you get real stuck just let me know. I can email you my cell phone
    number,

    Good Luck,
    Bill Jr
     
  7. James Sweet

    James Sweet Guest

    Cool, already did that actually, I noticed the joints weren't looking too
    healthy so I went over most of the power and sweep boards and resoldered
    anything questionable. Since the power supply started up with the blown HOT
    and blew the BUW12A the first time I'm assuming the PS will start up with
    the correct transistor, if not I'll cross that bridge when I come to it.
    Didn't notice any shorted semi's on the board, unless something else blew
    the second time around.

    Nice to know flybacks are still available, and apparently less expensive
    than I'd guessed, it's looking like this thing will work again some day
    regardless of the problem. Actually at this point I'm pretty much determined
    to fix it, as it seems the CRT's are in fairly good condition other than the
    contamination.


    The red coolant is fairly clear, but it looks like there's a few specs of
    dirt or something in it, but maybe not enough to matter. The green and blue
    have heavy growth of nasty stuff so they'll definitly have to be done. I
    found 24 oz bottles of coolant so I'll pick up two of them to make sure I
    have enough. Thanks for the offer for the help, I'm pretty sure I'll be able
    to figure it out but it's nice to know someone can give me pointers if I
    forget how things go together. What's the easiest way to get the tubes out
    anyway? Should I remove the whole bracket they mount on, or try to get
    individual CRT's out with the bracket in place? Should I remove them from
    the front of the set or the back?
     
  8. Bill Jr

    Bill Jr Guest

    Easiest to take the CRT's out from the front with screen removed.
    Simply disconnect the socket board, ground straps, remove anode wire from
    block and the 4 corner screws from the coolant chamber. On the older models
    like yours I usually remove the lens assembly first so that no coolant can
    get in or on the lens while doing the disassembly/cleaning process. Be
    careful not to break off the expansion chamber neck.

    Good Luck,
    Bill Jr
     
  9. BWL

    BWL Guest

    I've been doing these for years leaving the tubes in the set; a turkey baster
    with a short tubing extension (4"-6") will slip into the hole where the
    expansion chamber is attached. suck out as much fluid as possible, remove outer
    and inner lenses, clean everthing up inside the chamber, reassemble and refill
    chambers . I put a small piece of paper towel under the chamber opening while
    draining and refilling to catch leaks. Fill until fluid just starts to run out
    of hole, reinstall the overflow/expansion chamber, reassemble the screen , and
    usually only need very minor recentering to converge. I do the whole thing in
    about 90 mins, including time spent explaining to the kids.
     
  10. Bill Jr

    Bill Jr Guest

    Each to their own, but one primary o-ring leak years ago cured me of trying
    to do it by taking shortcuts. We also replace both seals for these. Not to
    mention cleaning with denatured alcohol to disinfect against future algae
    growth.


    Bill Jr
     
  11. James Sweet

    James Sweet Guest

    Where do you get the seals from? Nobody mentioned that before or I would
    have tried to order them too. Oh well, maybe I can coat the old ones with
    some silicone caulk, at least if it leaks it looks like it won't drip on
    anything important.
     
  12. Bill Jr

    Bill Jr Guest

    James,
    For your mom's set you can probably get by with cleaning the seals and
    reinstalling them.
    When we do this job at work and charge money for the job we want to
    completely cover our arse. It's only about 6 dollars more to replace the
    seals so we just do it.
    If you want the part numbers I can provide them, but I'll have to retrieve
    them from work tomorrow.

    Good Luck,
    Bill Jr
     
  13. James Sweet

    James Sweet Guest


    Ok I'll try to get by using the existing seals. I got the set for free
    anyway, didn't have room for it at the time so I had it stashed at my mom's
    place, now I still don't need it so I figured I'd fix it and set it up out
    there. I'll be able to check on it once in a while and make sure it's not
    leaking. I'm still waiting on parts to arrive, gotta get the electronics
    working before I bother with the tubes, I think I'll attempt to clean them
    out while in place in the set rather than remove them, I really dislike
    convergence adjustments, and if it's digital I'm not even sure I can get
    into service mode since I don't have the remote for it.
     
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