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TOSHIBA 53HX71 DEFLECTION ICs REPAIR
The Toshiba 53HX71 is an
older CRT-based rear-projection TV which has been
around since 1999. It represents a generation
of RPTVs which suffer from deflection IC failure
wherein the colors displayed tend to separate,
distort, and may not even show at all. Even
after multiple automatic alignment attempts, a
proper image will not be displayed because those
deflection ICs simply are past their usable life.
The 53HX71 utilizes 2x
STK392-110 deflection ICs, and twelve total
precision resistors. As you can imagine, this
is a factor of the three RGB primary colors used by
the TV to display an image. Searching for the
replacement ICs and resistors can be quite daunting.
Web searches yield multiple manufacturers, but we
decided to stick with Sanyo as the most reliable IC
vendor compared to the other China-made ICs.
Because this process isn't exactly trivial, we
preferred to go with the best so we don't have to go
through it again (assuming we acquired the cheaper
ICs which would most likely be less reliable).
An eBay search resulted in a merchant selling a
complete kit, including the twelve precision
resistors with higher wattages, and a 1% tolerance.
The STK394-160 seemed to be a popular item for the
53HX71 and similar RPTVs suffering the same problem.
Disassembling the 53HX71
is not too difficult. Dust will be attacking
from all sides, and a flashlight will be a great
help. Several Philips-head screws secure the
rear input panel, as well as the right-side video
processing PCB which holds the said ICs.
Several connectors and cables snake around, in and
out of the PCB, so all those need to be
disconnected. It is a good idea to count and
mark the location of each cable harness so as not to
forget how many were connected, and where each one
is plugged in to.
Once you have the PCB
out, the hard part begins. First, you will
have to de-solder the six large resistors feeding
each the deflection IC:
Here, the resistors are off. Note the presence
of a small voltage regulator with a small heatsink
in front of the left side STK IC. That needs
to be removed for easier access
Now, the right side IC is off, and also the VREG
module previously mentioned was also removed.
Next, you will need to
remove the deflection IC. You can either
de-solder each pin, or use the brute-force method.
For us, the brute-force method was more expedient,
but a bit riskier as well. We used
needle-nosed pliers to pull each pin out of the hole
as a soldering iron melts off the solder. Do
not use a high-wattage soldering iron as it will
damage the PCB and may render the whole thing
inoperable. You will also have to de-solder
the mounting points of the heatsink, and because it
is a gigantic heatsink, this is where a high-wattage
iron would be best used. We use an Ungar
adjustable iron for the precision de-soldering work,
and a 60W generic unit for the heatsink.
Once the ICs are off,
clean both sides of the PCB, carefully removing any
solder balls or other grime. Lighter fluid
works best for this task.
Remove the dead ICs from
their heatsinks, and clean off the heatsink grease
with acetone:
 
Before cleaning and
after cleaning with acetone
Next, apply a thin layer
of the best thermal interface compound you can get
your fingers on, to the back side of the new ICs.
You can then re-attach it to the heatsink.
Next, solder in the
resistors in their correct positions, then the new
STK394-160 ICs. Be careful as not to cause any
shorts, cold-solder joints, or PCB trace damage.
As you can see, the resistors were mounted far off
the PCB so as to promote airflow and cool them
during operation. Don't forget to re-attach
the VREG removed earlier!!!
All done!
Once you have verified
that all solder connections are as secure as
possible, make sure to solder the heatsinks as well.
Now, put the PCB back into the TV, and re-attach all
connections, cables, and harnesses. Cross your
fingers, have a fire extinguisher handy (just
kidding), plug in your TV into a surge protector,
and power it up. Give it 15 minutes to warm
up, and you should have a satisfactory image even
before re-alignment. If you see all three
primary colors at roughly the correct positions, you
are good to go. Unplug the TV while still on
(to discharge any energy in the coils and
capacitors), wait a couple minutes, then secure all
the internals with their respective screws.
This is also a good time to get the vacuum and suck
out all that cat/dog hair, dust, and dead insects
inside your old TV.
It took probably 5-10
power-on hours before the image stabilized
completely. Manual alignment had to be
performed a couple times in order to get the best
image possible. Good luck, and nothing beats
the feeling of accomplishing a repair where you
saved a couple hundred bucks by doing it yourself!
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