Cleaning, Balancing And Rejuvenating - B+K precision 467 Instruction Manual

NOTE
One or more LEAKAGE lamps may glow temporarily if the
FUNCTION switch remains in RESTORE position for longer than
15 seconds. Also, if returning to SET-UP to re-check leakage, wait at
least one minute to get a true leakage indication.
CLEANING, BALANCING AND REJUVENATING
Cleaning and balancing is a low energy restoring operation. It can be used
safely on all tubes to eliminate surface contamination causing high resistance
leakage or for further improving the emission of a fairly good cathode to restore
tracking or increase life expectancy. Rejuvenation is a higher energy procedure for
restoring cathodes when the emission is below usable levels.
High level rejuvenation of one gun can occasionally reduce the previous emission
reading of another gun, particularly if that gun had just been rejuvenated.
Therefore, after rejuvenation, it is often desirable to "touch-up" by cleaning and
balancing one or more of the guns in order to achieve good tracking.
B. CLEAN«BALANCE:
1. Set the FUNCTION Switch to the RESTORE position and the REJU-
VENATE/CLEAN.BALANCE Switch (17) to CLEAN*BALANCE. Wait
20 to 30 seconds. Observe the CRT heater for increased brightness from
the higher heater voltage.
2. Push and hold the RESTORE button (18), (19), or (20) for the gun to be
cleaned or balanced. The meter should rise immediately to a value near
midscale. After several seconds or more, depending upon the condition of
the cathode, the pointer will begin to fall. It usually will fall smoothly to
some low value.
3. Release the RESTORE button when the pointer reaches 0.2. If the pointer
drops erratically and then "hangs up" at a reading greater than 0.2, wait
several seconds and then release the RESTORE button. Also, observe the
Gl-K SHORT lamp. If it is glowing, remove the short before proceeding
further.
4. Return the FUNCTION Switch (1) immediately to SET-UP (if LEAKAGE
was being removed), or to TEST (if balancing or "touch up" was being
done). Resume testing.
5. If the CLEAN*BALANCE procedure was not successful and the condition
of the CRT is still unsatisfactory, use the REJUVENATE procedure.
C. REJUVENATE:
1. Set the FUNCTION Switch (1) to the RESTORE position. Set the
REJUVENATE/CLEAN«BALANCE Switch (17) to REJUVENATE. Wait
20 to 30 seconds.
2. Push and hold the RESTORE BUTTON (18), (19), or (20) for the gun to
be rejuvenated. The pointer immediately will rise to about 3A scale and the
RESTORE ballast (current limiting) lamp (21) will glow brightly. After
several seconds, the pointer will begin to fall. Often the pointer will fall
erratically or hesitate near midscale and then rise slightly before
continuing to fall. This behavior is usually accompanied by observable
sparking and Sputtering action between the grid and cathode.
3. Release the RESTORE button when the pointer reaches 0.4 or just as it
crosses into the red area of the meter. If the emission does not fall to 0.4
after several seconds, release the RESTORE button immediately. Observe
the Gl-K SHORTS lamp (16) to see if a short was created by the
rejuvenation process. If a short exists, use the REMOVE SHORTS
procedure.
4. Return to TEST. Allow time for readings to stabilize. A rapid judgment of
relative improvement can now be made. For greater accuracy, repeat
SET-CUTOFF.
5. Repeat LIFE and TRACKING tests. If slight further improvement is
needed, or if rejuvenation caused lower emission from one of the other
guns, use the CLEAN*BALANCE procedure.
6. If the CLEAN»BALANCE procedure after rejuvenation does not give the
necessary improvement, repeat REJUVENATE. Most cathodes will achieve
90% or more of the possible improvement in a single operation. Some will
require two or three cycles of rejuvenation for maximum improvement.
Further rejuvenation generally causes lower emission and shorter life. The
fewer rejuvenation cycles that are used to achieve satisfactory emission,
the greater will be the life expectancy.
NOTES
If the meter pointer does not rise when the RESTORE button is
pushed, it indicates that successful rejuvenation is probably not pos¬
sible. If the reason for lack of emission is an extremely inactive (con¬
taminated) cathode, it is sometimes possible to start the rejuvena¬
tion process by applying even higher heater voltage than normally
used for rejuvenation. To try this, go back to SET-UP and increase
the heater voltage approximately 25% above the normal setting
(8.0V for 6.3V tubes). Then return to RESTORE and attempt
rejuvenation. Since the tube is not useful anyway, the risk is small.
The greatest danger is that excessive heater voltage will expand the
cathode so far that a short to G1 will be created. Also, of course, the
heater itself could be burned open by the higher voltage, although
this occurs less frequently than a short.
If all three guns show initial low emission (BAD), rejuvenation of
one gun will often result in some improvement of the other two
guns. (This is caused by the elevated heater voltage which is a mild
form of rejuvenation in itself.) These guns should also be reju¬
venated, however, even though the emission may have been
improved enough so they read in the GOOD region.
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