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Sony/HP Monitor & Dynamic Focus

Discussion in 'Electronic Repair' started by JM, Feb 7, 2004.

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  1. JM

    JM Guest

    I have an HP 21" 4576A monitor (Sony Trinitron) with a focusing problem.
    I've posted about it before, but the short version of the story is that I
    can adjust for good center focus, or good focus on the sides, but I have to
    find a compromise between the two most of the time.

    Someone replied to my last post and mentioned that they had run into the
    same problem on some smaller "made by Sony" monitors, and it turned out to
    be due to some cracks in a transformer in the dynamic focus circuit.

    Now, I just got the monitor back from a local tech, who adjusted the
    convergence, alignment, purity, focus, and gray level, which has resulted in
    a whiter, cleaner looking picture, but the focus when I got it was worse
    than when I took it in. Also, the onscreen convergence settings were way
    off the factory defaults, and the convergence was crap, until I reset them
    back to factory. Odd. Anyway, I adjusted the focus back myself, at which
    point I had a really nice crisp picture, even at full contrast, which I
    couldn't get before.

    This was last night, and today when I turned it on, I was back to the same
    problem I had originally, where the edges of the screen were well focused,
    but the centre was blurred out a bit. Horizontal white lines were showing
    twice. I waited for things to warm up to see if it would go away, but it
    didn't change at all. So I tweaked one of the focus adjustments again
    (luckily they are accessible through the vents in the top of the case) and I
    was actually able to get the focus in both the centre and the sides pretty

    So I'm wondering, it sounds like dynamic focus is designed to adjust the
    focus "dynamically" based on some changing parameters (maybe temperature?).
    If that's the case then it sounds like I do indeed have a dynamic focus
    problem, most likely the one that was mentioned in reply to my other post.
    I can't find that post now, but a bit more info on that would be
    appreciated, I have another shop that will give me an estimate for $25, so
    I'd like to be able to relay to them this info on cracked
    transformers/dynamic focus problems.

    Thanks in advance,
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