Table of Contents
Advertisement
F.
LIFE TEST:
1.
With the FUNCTION Switch in the TEST position, depress and hold the
LIFE pushbutton
(14)
and allow the emission readings to stabilize. For
acceptable long term CRT performance, the readings should stay in the
green (GOOD) area. The less the emission drops, the longer the life
expectance of the tube.
2.
While holding down the LIFE button, depress the TRACKING button and
perform the TRACKING test of Step E. For acceptable long-term
performance, the CRT should maintain tracking with the LIFE test button
held down.
3.
Release the LIFE and TRACKING buttons.
4.
If life expectancy is poor, proceed to CLEAN«BALANCE.
NOTES
Other clues for judging life expectancy are obtained by observing the
"warm-up" and "cool-off' behavior of the cathode. To make these
observations in the TEST position, press any RESTORE pushbutton
(18, 19, 20).
This interrupts the heater circuit and makes it possible
to observe the rate at which the emission rises and falls as the
cathode heats up and cools down.
Since the emission from all three guns of a color CRT is displayed
simultaneously, significant differences between cathodes are easily
observable. If, for instance, during warm-up, one gun reaches full
emission much slower than the other two, it is an indication that
there may be very little good material left on that cathode or that its
heater has been dislodged away from the cathode causing lower than
normal cathode temperature. In either instance, it is a further
indication that short life may be expected from that gun. A good
tube will reach full emission levels and will track within two
minutes.
Similarly, the "cool-off' characteristic can provide another clue for
judging life expectancy. Observe the time it takes for emission from
each gun to fall after the heater voltage is interrupted. If, for
instance, two guns maintain full emission for 7 to 10 seconds, and
the third gun falls rapidly after 3 or 4 seconds, short life can be
expected from that gun.
G.
FOCUS ELECTRODE CONTINUITY TEST:
With the FUNCTION Switch in the TEST position, depress the FOCUS
pushbutton
(15).
Observe the FOCUS-OK lamp
(15).
If the FOCUS-OK lamp
glows or flickers, the focus electrode continuity to the tube base pin is good.
12
i
i
I
NOTE
It is also possible to check for an open interconnection in color
CRT s, with individual focus electrodes that are internally connected
by welded straps. To do this, push the FOCUS test button and
observe the 3 emission readings on the meters.
If all 3 meter readings drop approximately the same amount, the
inter-electrode continuity is good.
If one or two meter readings drop slightly whil^ the other drops to
near zero, there is no continuity to the focus electrode of the
low
reading gun,
even though the FOCUS-OK lamp glows.
If the tube tests bad for focus continuity, a decision to replace the tube should
be based on actual performance in the TV set. If the focus is not objectionable
to the customer, the CRT need not be replaced.
RESTORING THE PICTURE TUBE
The Model 467 employs three restoring functions: REMOVE SHORTS,
CLEAN*BALANCE, and REJUVENATE. All three are available in the RESTORE
position of the function switch.
LEAKAGE AND SHORTS: Excessive leakage or a short between the control
grid and cathode will show up in the LEAKAGE test that is automatically
performed during SET-UP. A low resistance short (less than 20k ohms) can be
removed by the REMOVE SHORTS procedure. High resistance leakage is most
successfully removed by the CLEAN*BALANCE procedure. If grid-to-cathode
leakage was indicated in the LEAKAGE test during SET-UP, use the following
procedure.
A. REMOVE SHORTS:
1.
Set the FUNCTION SWITCH to the RESTORE position.
2.
Observe the Gl-K lamp (16). If it is not glowing, a high resistance leakage
is indicated; use the CLEAN»BALANCE procedure.
3.
If the Gl-K lamp glows, push the REMOVE SHORTS button (16) and
release. If the short has been successfully removed, the lamp will not glow.
4.
If the lamp continues to glow, repeat Step 3 several times. Wait 5 to 10
seconds between operations. If the short has not been successfully
removed, reduce the heater voltage by turning the HTR RANGE (3)
switch to the lowest range. If the Gl-K shorts lamp goes out as the
cathode cools, it indicates that the short may be due to mechanical
expansion of the cathode. Such shorts usually cannot be removed.
5.
After the short is removed, resume the testing procedure.
13
Advertisement
Table of Contents
Need help?
Do you have a question about the 467 and is the answer not in the manual?