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Toshiba 42HP66 minus reds & yellows

2188 Views 6 Replies 3 Participants Last post by  74f100
I would imagine it being difficult to diagnose issues with out testing, but, let's see if this sounds familiar.

Toshiba 42HP66 : was my sons - he replaced, and gave it to me as 'non-working'. I blew out the dust, and ran each day for a week, no problem. Then today, after running for a short time, the picture went to a grainy, contrasty, with blacks, purples, and teals, but little or no reds or yellows - much of the picture washes out toward white...
Turn it off for a while, then back on, and the picture is back for a short time before problem returns...
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Sounds like a thermal problem, bad connection, or bad caps. First thing to test is for thermal effects.
OK - thanks for the direction :)

Gently heated the ysus boards big sink, and no change.

Cooled it all down, and gently heated the Zsus boards big sink, and wha-la - problem rears it's head.
Cooled it down again, and has been running fine for the last hour with the help of a fan.

So, is this the classic problem with bad paste on the heat sink?

What's next?
Ran for another while, and eventually heated to having the problem even with the fan running on the sink...

Looking at these: it appears the chip is screwed to the sink, then soldered in - so re-doing entails un-soldering the chip from the board? (am I seeing this right?)

Are my findings telling me it IS a thermo issue, and therefore NOT a cap issue?

Thanks for the help!
I would lean towards cold solder first. Look very closely at the bottom of the board on the sustain IC's for bad connections. Then caps, then Thermal breakdown of the IC's themselves.

I hate to do this, as it's not green, nor my style, but, after re-soldering the IC, to no avail, and not being TV savvy, I'm going to quit wasting your time - and mine. I'm calling it dead - question now: landfill, or?

I will say this: todays tests - she went very quickly to her problem - as if not heat related, but perhaps the longer period of time she sits unplugged, the longer she'll run before problem arises.
Or try going to Shopjimmy.com and see if they have a replacement... Take very careful note of the part number.

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