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Samsung projection convergence

Discussion in 'Electronic Repair' started by Ken G., Oct 12, 2005.

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  1. Ken G.

    Ken G. Guest

    These tv sets are at work in a corner so i dont have the model numbers
    but i`m sure some of you would have seen these by now .
    Last years model . The cabinets are totaly plastic , the set is not very
    tall .
    I have 9 of these sets saved and all have severe convergence distortion
    on the picture .
    The convergence module on these hangs on the metal support that holds
    the 3 tubes .
    the module has 2 large STK chips on them that i suspect is the problem .

    Is there a reason so many , perhaps ALL of these sets have this problem
    ? is there a hidden KNOWN problem on these making it a waste of time
    ordering that many STK chips ?
    The sets belong to a salvage store where i work on the electronics . I
    am not an expert but can replace such parts . They dont want to spend
    hundreds getting these fixed so a service shop is out .

    Thanks.
     
  2. Ken G.

    Ken G. Guest

    I went looking on the net for these pieces of crap and cant find any .
    They may be 2 or 3 years old ?? They are still coming in as store
    returns so ??
     
  3. Guest

    First of all, use lateral thinking, later it will lead you to
    omnidirectional thinking. Change the chips on ONE board and run it
    through all the sets, one at a time. Make sure to check everything that
    even looks fusible, and of course see it work in at least one set. Once
    it works transfer the board from set to set. All the ones it works in,
    order chips for them, and get one extra set for a board you keep, to
    fix the rest.

    You don't even have to screw the board in, just plug them in. The ones
    that don't work, go farther, but at least (hopefully) get the bulk of
    it out of there. ( or fixed, whatever ).

    You need to get to know what the picture looks like without convergence
    correction, this way you can make (in the future) an educated guess as
    to what's wrong.

    Once you got X amount of them fixed, go on to the rest.

    Yes, I'm a pro, but I still work for an old horse trader. When you lack
    detailed service info, multiple identical units are the best thing to
    have.

    JURB
     
  4. Art

    Art Guest

    Also, Inspect the sets throughly for any signs for coolant leakage from any
    one of the three crts. This is a very common problem in Samsung / Akai RPTV
    CRT sets. Any incidence of finding fluid will preclude how you will attempt
    servicing them.
     
  5. Ken G.

    Ken G. Guest

    Thanks guys . I did look for coolant leaks and none had it but i have
    seen it in the past and junked those sets for parts .

    The models are Samsung HCM 4215W and AKAI PT4298HDX/SMS
    Both models have P55A chassis .

    I like the idea of buying 2 or 4 chips and try the circuit in all . I
    did save a couple by using chips from leaker sets .
    I was concerned a bigger problem caused these chips to fail in so many
    sets .
     
  6. Guest

    Hey Ken, I have the same problem with my tv (Samsung HCM4215W) and was
    wondering if you were able to fix yours. My local repairman said the
    estimate was $300 for a convergence module, but from reading online, it
    seems like I just need either two new IC's, or a new convergence board
    with the two IC's. Any help?
     
  7. Jason D.

    Jason D. Guest

    Ask the shop that tech works for, is this shop he works for samsung
    servicer authorized? This is only way shops can get service manuals
    and schematics for Samsung stuff.

    300 estimate is about right. I have done many of these.

    Cheers, Wizard
     
  8. Ken G.

    Ken G. Guest

    I found the chips on line for 15$ each . We dont want to spend much on
    these so 4 chips were ordered and on the way .
    I will replace them on one board and make sure all those fuse resistors
    are good then try it out .
    Any sets that it fixes will get more chips ordered .

    I know all about buying cheap parts but this is orders from headquarers
    If it dont work the sets go away broken .
     
  9. Rates will vary, but $300 is not out of line in many markets. We usually
    repair the boards rather than replacing them. Like many repairs, these can
    be a can of worms for someone not familiar with doing these repairs.

    You can buy the manuals from distributors or download them from several
    sites where shops share manuals, or get them from another shop that is
    authorized, just like the way you can get tips from other servicers. We are
    not Samsung authorized and this is one manual that I got from Tritronics for
    a little over $10.

    Leonard
     
  10. Guest

    Hey thanks Jason :)

    So what exactly is the convergence module? From looking at the tv set,
    I can see the two IC's, connected to the convergence AMP board, that
    sits in a metal alloy heat sink, that is screwed/hangs right behind the
    three crt's. Even looking around via google, I can't seem to find any
    replacement convergence module's, or even any pics of it. What does it
    look like? I did find a thing infront of the middle (green) crt board
    with some numbers on it (sorry!) with a label like VM008 something.

    Also from reading around, it seems like the convergence module costs
    $300, so are they even charging me for labor? How much would a
    convergence module cost on its own?

    So, from what the serviceman told me (a new convergence module) would
    getting a new convergence amp board (AA95-2002A is the one being
    recommended), with two new convergence IC's (STK392-040) fix the
    convergence problem I have?
     
  11. Jason D.

    Jason D. Guest

    I'm not sure where you got the prices, but we can't tell you the
    actual prices, just only the retail prices that customer sees along
    with labor rate. We have to earn our keep to put our meal on the
    table and have roof over our heads and pay for shop's overheads.

    Also good shops had to be careful of fake components including ICs.
    They do exist out there and I have seen this happen.
    The tech was doing safe way out by replacing both ICs to cut down on
    call backs and make you happy. Many times we get away with just one
    just that we know WHICH IC is the dud by looking at the images on tv.
    After that, touch up adjustment to convergence and memorize it so
    autofocus or autoconvergence will work correctly. This is reason for
    schematics and service manual. It is about 50 pages long and also
    that cost pretty penny.

    To others doing this same on removeable Samsung convergance amp module
    that mounted to the CRT steel frame, I put dollop of thermal grease
    around that screw hole (goes on between this heatsink and the steel)
    to improve the heat transfer ditto some thermal grease to the IC even
    module already have thermal pad.

    Plus we must repair to component level since cost of a complete module
    assembly is too expensive even for warranty job even let alone to
    customer.

    Cheers, Wizard
     
  12. Jason D.

    Jason D. Guest

    Ken G.

    This is not good idea to appoach this. Make sure that ICs is real
    thing not fakes. The ICs on these convergence designs run very hot
    and ESPECIALLY that samsung is using these ICs in place of convergence
    rings. Oh boy. Many samsung models didn't come with these rings on
    the yokes. By the way, the convergence windings is about 20 turns on
    each one of four sectors on the ferrite ring. Very, very low ohms for
    the poor IC to drive them.

    Cheers, Wizard
     
  13. What do you mean by "ICs in place of convergence rings?"

    The inductance on the Samsung convergence yokes are not much different than
    other brands. They tend to run a little hotter than some that use the same
    chips, but virtually every manufacturer that uses these outputs has similar
    reliability. Some use more or less resistive loading on the outputs, but
    they all run pretty hot.

    Leonard
     
  14. Jason D.

    Jason D. Guest

    Well, with active convergence disabled, the convergence rings that you
    get green CRT centered then move other two CRTs convergenced to that
    green in the center (usually!) or other models had red and blue set
    certain distrance from green and finish rest of way with convergence.

    Now, many Samsung units did not use the rings. Relying on ICs to push
    all the beams together is very hard job for both STK ICs, hence runs
    much harder and very hot. That's the reason for fairly high failure
    rates.

    Think of a thick wall tube about 1/2" length, that's the ferrite core,
    four windings in one layer in four sectors, each sector 20 turns
    around the core (toroidal). The assembly goes through the CRT's neck.
    Others like RCA uses 4 poles with more turns around each pole and
    easier to pull beam around and less stress on the convergence amps.
    Oh yeah, Samsung sometimes used sloppy solder joints (just magnet wire
    and wirings twisted together & soldered. I had one come apart once.

    I have yet to see convergence of this Thomson (RCA) discrete
    convergence amp design fail YET except for rare thermal defective,
    only happened once and was fixed by co-worker 2 years ago.

    Cheers, Wizard
     
  15. I have never noticed that they did not have centering magnets. Every one
    that I have done was pretty close after repairing the output module. In
    other words if the variance in the yokes is very large, they have to correct
    the excessive offset with dc bias? Not a good design, IMO. This would make
    them run hot. The last one that I measured ran at about 60 degrees C,IIRC,
    pretty typical for the STK392-040. That is with the back off. They likely
    run hotter with the back on, due to the fact that they are mounted so high
    in the set compared to other brands. Also a dumb design, IMO. Never saw
    one where excessive bias was the case, as one thing we always check is for
    dc ofset of more than a couple hundred millivolts on the outputs ( a habit
    developed in the old Novabeam days...). But then, I have only done a few of
    this set and they were pretty routine, except that tweaking the convergence
    is a PITA and the various adjustments seem to interact a lot.

    Leonard
     
  16. Jason D.

    Jason D. Guest

    Leonard,

    Yes, run HOT!

    Using bias to position all CRTs instead of rings.

    Usually you get good results with just a IC, except many I had to
    replace burned resistors and fuse then have to slightly adjust
    convergence and memorize it with autofocus while still in service
    convergence mode.

    When I have chance I'll take a pic of samsung convergence coil
    assembly.

    Cheers, Wizard
     
  17. Every one that I have done has needed resistors and fuse also.

    Samsung's price on the output ICs is ridiculous, too. Are they trying to be
    Sony with respect to parts prices, or what? At least Sony is starting to do
    something about it.

    Leonard
     
  18. Guest

    Thanks, again, to everyone that replied :)

    So, from this website, Vancebaldwin.com, what would be the best part
    for me to get :

    AA95-02002A ($65.68)

    Or :

    AA95-02002A ($178)

    Or :

    BP94-00383A ($70)

    My question is, do these boards come with the two new IC's already
    soldering onto them? Will they be good IC's, not cheap ones? Also,
    whats with the different prices? The BP94 model is listed as a
    "substitute" model, but it's also listed for the HCM4216 model, not the
    4215. Would it run ok on my television? Just sorta confused...

    Again, thanks for the help you guys :)
    Eric
     
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