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toshiba 42wp48a plasma screen requires warm up?

 
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matthewy



Joined: 24 Dec 2008
Posts: 14

PostPosted: Sat Jan 29, 2011 7:14 am    Post subject: toshiba 42wp48a plasma screen requires warm up? Reply with quote

I'm trying to fix a plasma screen (toshiba 42wp48a) but suspect the problem may be a common one and may have a simple approach for repairs.
I'm not a experienced repair person but have done lots of repairs to simple problems including replacing caps from motherboards, finding shorted diodes and replacing them etc (simple stuff to highlight my level).

The issue I'm having is that the plasma screen shows picture when you turn it on but its very distorted / unstable as if you are tuned to a weak signal, however this is av and the menus reflect thesame. The colours are very odd as though you have reduced the colour down to say 16 colours or 256 colours etc (think of taking a jpeg image and photoshopping it downto a pelette of 16 colours) with smared lines. After afew mins of being on, it solowly gets better and after about 20 mins, it looks about right.

Is there a approach to investigating the issue? I've opened it up and theres nothign that stands out like bad caps, however, i am well aware parts can be bad even if they do not show the signs.

Thanks
Matt
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Munchkin



Joined: 20 Nov 2010
Posts: 4
Location: South Africa

PostPosted: Tue Feb 01, 2011 12:52 am    Post subject: Plasma colours odd until it warms up Reply with quote

I have had what sounds like the same issue. I haven't had an LCD I couldn't repair yet, however I'm rather inexperienced at this point when it comes to plasma. I purchased a second hand SONY unit from a friend who is also in the repair business. Internals are LG V7. on firt power on there were couloured "pixels" bleading from the left to the right of the screen. They would slowly dissipate to the left of the screen as it warmed up.....I was already suspect about the YSUS. I took it anyway as I had a customer needing installation for surveillance purposes in his supermarket. I took it home first, dissassembled and checked the buffer boards as well as YSUS. I also checked voltages and waveforms on the SUS board all seemed OK. About a month later I was alerted to the fact that the unit was no longer displaying picture. Failure looks typical of YSUS now.I have two LOGIK 42" with SAMSUNG S42AX-YD01 internals both with very obvious YSUS and buffer failures which have been awaiting parts. They arrived today, first I was fuming when I noticed tell tale signs of refurbishment, I don't mind refurbished boards, but then I would like to see documentation with each board regarding rework....I come out of a satcoms development background and have spent time in production rework. Such documentation should exist and if not the company doing rework is surely not certified by SAMSUNG. Anyway all did check out OK. I stripped unit down and cleaned them thoroughly as they have been standing for roughly four months and re-checked voltages on PSU before populating panel with new boards. replaced YSUS, Xmain and buffer boards on both units and powered up with HDMI source. colours looked a bit odd, then I dragged a VLC media player window accross to the unit and had horrible flooding of green ...almost like a bad mpeg layer 4 file does when you scan forward.also noticed my window backgrounds were also off colour.I immediately turned off and reverted to waveforms. My only problem is I'm currently sitting with only a velleman HPS10 single trace oscilloscope for testing and adjustment. any suggestions on best way to perform this setup with my current test equipment situation?
I would hate to discover my worst dread right now.....that I have been sold boards that have not been thoroughtly checked and still have degraded components on them.
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Munchkin



Joined: 20 Nov 2010
Posts: 4
Location: South Africa

PostPosted: Tue Feb 01, 2011 1:34 am    Post subject: SAMSUNG S42AX-YD01 green picture Reply with quote

Just plugged a DVD player into one of the units that were displaying strange colours when connected to PC via HDMI everything is fine on AV input, seems the input board's HDMI is lacking.....Two units doing the same thing I'm assuming the HDMI scaler was of the first generation??
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