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Old 08-01-2018, 10:54 PM
Sealtest Sealtest is offline
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What causes the HV transistor to blow but nothing else? Samsung k-50

Here's an odd question. I am working on a small Samsung tv chassis model k-50 that I got from a closed tv shop. The problem with the set is that it turned on, then off (the lady who owns the remnants of her father's shop powered it up before she could be stopped). This may have been what did the damage but anyways the set blew the 500ma fuse and the transistor for the HV ( Sk9119) was bad. I went through the set and tested Q401,Q402,Q501,Q502,Q202,Q606 and all were good.

So my question is what caused SK9119 to blow when all else is good? In other threads I mention having years of xperince working on vintage hifi gear but it seems that this doesn't convert over to TV repair. With hifi if the main transistor is blown in a channel, or a main transistor is blown in a power supply, there is always a string of dead components. So far that has not been the case with TV sets with me. Do they have more protection or something?
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Old 08-02-2018, 03:49 AM
Telecolor 3007's Avatar
Telecolor 3007 Telecolor 3007 is offline
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Maybe poor manufacturing qualty or less tollerance to faults.
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Old 08-02-2018, 07:22 AM
zeno zeno is offline
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Sometimes they just blow for no reason BUT.....
Since it was changed before you need to run the set on reduced
voltage to trouble shoot. I put the process out last week
http://videokarma.org/showthread.php?t=270707
If its NOT a remote start at 60V & slowly turn up.
You can run it a few seconds then feel the horz out. If its hot
you probably got a bad flyback.

73 Zeno
LFOD !
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