- Only the heater pins should have resistance. All other pins have infinite resistance to each other and to either heater pins.
- Used picture tubes that have a heater-cathode leakage/short have a low restoration success level.
Symptom
|
Suspect
|
Check
|
Procedure
|
Dark picture or one color missing.
|
Heaters Open
|
Apply 6Vdc to
the heater terminals.
Some heaters
are connected in parallel,
others in
series but all
take 6Vdc.
|
·
Clean the CRT pins and examine the socket for corrosion.
·
Apply 6Vdc to the CRT heater pins, looking for a glow in
all three heaters.
|
Dark picture
|
Grid 1 to Grid 2 short.
|
There should
be infinite
Resistance between the G1 and G2 pins.
|
·
Unplug TV and remove C board
|
Bright red,
green or blue picture.
One color
retrace lines
may be
present.
Retrace lines
are diagonal lines that run
from lower left to the upper right corner
|
Heater Cathode
short.
OR
Cathode to Grid 1
short
|
·
Remove the R, G or B video input to the CRT for the bright
color.
·
If that color is still bright, the tube is bad.
|
|
Bright picture
with retrace lines and/or
poor focus.
|
Grid 2 to high
voltage
Grid 3 leakage.
|
Symptom is that all three colors are bright
|
Reduce G2 /
screen voltage to the lowest setting.
Vary focus
control to both limits several times.
Put on safety
apparel.
Place the tube face down and lightly tap the neck to
dislodge the particle.
|
RGB Rainbow
Purity / Beam landing is off.
|
Aperture grill
was
unseated in transit
The TV s
degaussing
circuit did
not
demagnetize
aperture
grill metal support.
|
Rainbow of
colors can
start at the top or bottom (bottom rainbow shown).
Same color
blotches
remain at that
area of the screen regardless of picture screen
changes.
|
A loose
aperture grill is
dangerous and
may cause tube implosion. Use all
safety
precautions.
Do not jar set.
Transport TV face down.
Do not manually Degauss the picture tube with a strong
degaussing coil.
Repair the TV
s degaussing circuit. The thermistor or
cold solder is usually at fault.
|
