Scan Board & IC Troubleshooting
Pioneer Plamsa TV _ Scan IC Removal & Re-installation _ Pioneer Plasma TV
Almost all plasma displays will have same circuit configuration; irrespective of its brand name.
First determine which scan board has the problem by doing a diode
check between VH and GNDH after disconnecting the ribbon cable between the Y drive
and the upper and lower scan assembly.
To some panels, you have to remove the blue glue by using flux remover
or acetone. Measure between the output pins of the scan ICs and the bus bar on
the scan board using either an analogue meter or a digital meter in manual
mode. All outputs on all scan ICs should
measure about the same resistance [between 300 to 600Ohms]. If not, that IC is defective. Remove it and then re-check VH. There can be more than one bad scan IC.
Checking drives and Scan ICs.
Do not operate with any connectors unplugged. Replacing scan ICs in home is not
recommended. If scan board is
disconnected, be sure to isolate buss bar also.
Discharge all scan board connections including buss before
reconnecting. Unplug power connector
from the X or Y drive. Perform diode
check with DVM from Vsus to ground.
Should check as a diode. If Y
drvie is horted, next unplug scan PCBs.
If short goes away, check scan ICs.
If still shorted, replace the drive.
With scan PCB unplugged, perform diode check from Vh to Psus [bus
bar]. Should check as a diode. Ifg shorted, check the resistance from Vh and
Gndh [buss bar] to HVxxx (each IC has 2 test pads). Should measure 3 to 5 Meg Ohms. Remove IC that measures different from other
and recheck. If all check is the same,
but Vh is still shorted, check all 64HV pins of each IC. Remove side rail, and 32 feed throughs are
accessible near the panel connection. If
nothing shows up, loosen Scan PCB and flip over to access all 64 connections.
How to replace the SCAN ICs
There are two methods
With a nozzle type soldering station
With the CHIPQUICK SMD1 removal kit
With a nozzle type soldering station
With the CHIPQUICK SMD1 removal kit
With nozzle type disordering station
Mount the right type of nozzle.
Add solder to all pins of the defective
SCAN IC
Heat up all pins with the nozzle. When
solder reflows, remove IC with pick up tool.
Remove IC and clean PCB. Check PCB for
damaged patterns and short-circuits.
Once the IC is positioned, tip it
diagonal so it cannot move anymore.
Solder two opposite corners.
Solder all pins and check very
carefully for dry joints or short circuits.
With Chipquick
Another way to remove SMDs is with a
special solder made by Chip Quik.The solder is an alloy of tin, lead, indium, and
bismuth. Bismuth has a very low thermal conductivity. If it is mixed with tin,
the melting point is reduced to 65°C. and so it becomes difficult to damage the
PCB . Another advantage is that there is no additional desolder equipment required. It can be ordered with part number SMD1. This
package contains chipquick flux , chipquick solder and alcohol pads.
Apply flux to all pins of the defective
SCAN IC.
Adjust the temperature of the solder
iron to +/- 200°C and melt CHIPQUICK alloy uniformly on all pins.
Maintain the alloy in molten state and
remove the SCAN IC with a pick - up tool.
Move the excess with the solder iron to
an unused section of the PCB. Remove
after it is cooled down.
Clean site with swab dipped in flux
while applying heat.
At room temperature, clean the residue
with alcohol pad.
PCB is ready to mount the new SCAN IC
How to remove the coating of SCAN IC.
Peel the coating a little at the lower left corner of the SCAN IC
which has rather more coating. (be careful not to damage the pattern.)
Make a notch at the peeled coating.
Pick up the peeled coating by tweezers, and wind them around the
point of the tweezers while rotating tweezers.
Peel off the coating while rotating tweezers along the SCAN IC After
all the coating around the SCAN IC is peeled off continue.
After removing the larger portion of blue glue with a pair of tweezers,
spray the IC pins with flux remover and scrub with soft brush. Let stand and repeat several times to remove
and soften the glue under the IC.
When positive all blue glue has been removed from the leads and
underside, proceed to the removal steps. [Glue not removed from the IC pins or
underneath chip could result in a damaged PC board at the time of IC removal.]
