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CRT Coolant Flush/Renewal instructions for Sony KPR-4150 RPTV:
NOTE:
These instructions may apply to similar televisors, but
to the author's knowledge are specific of the KPR line
from Sony. The author accepts no liability and provides
no warranty for the information contained in this
document.
June 2004,
Jonathan Moore Liles
----
There are two methods for changing the coolant fluid in
these CRTs. One is invasive and is akin to refurbishing. The
other is much less labor intensive but may be ineffective
depending on the stage and severity of corrosion inside the
CRT coupling.
Firstly, allow me to state the facts of the issue as I have
come to understand them through process of experiment and
investigation.
PROBLEM:
These CRTs have a partially painted aluminum casing such
that the aluminum surfaces inside the coolant reservoir are
in constant contact with the coolant.
The coolant used by Sony is a highly concentrated solution
of Ethylene Glycol.
Ethylene Glycol decomposes at temperatures around 187
degrees Celsius in the presence of oxygen and copper or
aluminum, degrading into five organic acids: glycolic,
glyoxylic, formic, carbonic, and oxalic. This process is
corrosive to copper and aluminum. The threshold for
decomposition is lowered with the boiling point of the
ethylene glycol solution. DECOMPOSED COOLANT IS WORTHLESS
AND SHOULD BE DISCARDED.
The end result being the corrosion of the aluminum reservoir
and the deposit of corrosive by-products (aluminum oxide?)
onto the glass of the CRT and convective divider, causing a
blur in one or more colors (tubes) and in all or part of the
screen area.
SOLUTION:
The only solution is to remove the spent coolant, clean
and/or repair the reservoir, and refill with virgin coolant.
Both of the following methods require the removal of the
affected tube(s) from the chassis. This is relatively
simple:
Remove the focusing rack (connected to the CRT coupling
by four screws)
Disconnect the high voltage anode leads from the red
splitter block by pushing in and turning 90 degrees. The
anode cups are permanently sealed to the CRTs and
removing the cup end is unnecessary and dangerous.
Discharge the tube to ground without electrocuting
yourself.
Disconnect the tube while leaving the yoke attached and
intact. This may require desoldering the 2-4 convergence
wires. Be sure to note the order as incorrect assembly
may damage the convergence circuitry.
Finally, remove the tube from the set.
THE HARD WAY:
Remove the two drain screws. Extract the spent coolant with
a syringe or pump (there should be slightly more than 6
ounces). With a 1 inch long razor, cut through the silicone
sealant between the CRT face and the lens assembly. This is
easier than many people think: Insert the blade until you
feel a release of pressure. Remove it. Advance the width of
the blade. Repeat over circumference.
Once the lens assembly and CRT have been separated, the
corrosion should be visible. Do not attempt to remove it by
scrubbing. Soak both halves in WHITE VINEGAR (a %5 acid) for
thirty minutes to an hour, agitating regularly (but don't
get the yoke wet). This should dissolve the deposits from
corrosion. Look carefully at the pitting. Can you see the
shine of bare aluminum at the bottom of the pit? If
not--continue soaking. Rinse with hot water one the
corrosion has been removed.
Scrape all of the old silicone sealant from the mating edges
of the assemblies.
Use painter's tape to tape off the glass face of the CRT and
the glass of the lens assembly. Be certain to tape over the
opening into the lens cavity (located between the acrylic
front lens and the convective glass divider)! At this point
you can safely polish the mating surfaces of the assemblies
with emery cloth or some other abrasive to give the silicone
sealant a suitable bonding area. Tape over the mating
surfaces, as they should not be painted. Paint both units
with FLAT BLACK ENAMEL spray paint (high-temp engine block
enamel works well). Be certain that no bare aluminum is
exposed on any inside surface. Let the paint dry for the
period recommended on the can (usually overnight).
Or, for a slightly quicker method, paint the inside cavity
by hand with quick drying BLACK ENAMEL PAINT (perhaps auto
touch-up paint, or model makers paint), which should dry
completely in thirty minutes to an hour.
Once the paint has dried remove the painter's tape and clean
the glass surfaces one last time with a solution of water
and alcohol OR ammonia.
Lay the lens assembly down so that the mating surface faces
up. Apply a quarter inch wide bead of GE Silicone II Black
RTV (non acid-cure) sealant . Gently lower the CRT mating
face until the two meet. Apply slight force. A small bead of
sealant will be displaced from the seam.
Let silicone cure for 24 hours.
Use a clean syringe to fill the reservoir with 6 ounces (180
CC's) of VIRGIN COOLANT. Leave a few bubbles at the top:
they relieve the pressure and keep the unit from leaking or
rupturing.
Reinstall both drain screws. Reinstall the CRT into the set.
THE EASY WAY:
Remove the two drain screws. Extract the spent coolant with
a syringe or pump (there should be slightly more than 6
ounces). Fill the reservoir with 6 ounces of WHITE VINEGAR
(a %5 acid). Reinstall the drain screws and allow unit to
sit for several hours (or overnight), agitating regularly.
This should dissolve the deposits of corrosion. Remove the
two drain screws. Extract and discard the spent vinegar.
Refill half-way with 3 ounces of hot water (preferably
distilled, de-ionized, or de-mineralized), agitate, drain,
and repeat.
If any products of corrosion remain in the reservoir they
will pollute the new coolant and result in more deposits on
the glass. The process of corrosion, however, should not
resume unless the coolant breaks down due to extremity of
heat or time.
Drain all water from the reservoir. The coolant will absorb
water from the atmosphere, so a few drops left in the
reservoir won't hurt.
Use a new syringe to fill the reservoir with VIRGIN COOLANT.
Leave a few bubbles at the top: they relieve the pressure
and keep the unit from leaking or rupturing.
Reinstall both drain screws. Reinstall the CRT into the set.
REPLACEMENT COOLANT:
There are several existing formulations of CRT coolant. One
may, of course, order some from the manufacturer, but one
must also be willing to pay a premium. The raw ingredients
of most CRT coolants vary little from such common items as
toothpaste, eye-drops, automobile antifreeze and KY liquid.
The following are formulations that I consider viable:
80% Propylene Glycol
20% Glycerol (glycerin)
This is the preferred formula, and is the most like those
provided by electronics supply houses. Propylene Glycol is
non-toxic and has better thermal durability characteristics
than the Ethylene Glycol found in commercial products.
Propylene Glycol is less likely to degrade or become
corrosive. It is also easier to acquire locally through
pharmacy, veterinary, and restaurant suppliers. Glycerin
is also widely available, however usually more expensive
than propylene and ethylene glycol.
60% Distilled Water
40% Glycerol
Water is a more effective thermal transfer medium than all
of the other chemicals mentioned in this document.
Unfortunately, it has a high freezing point and a low
boiling point relatively. Freezing or boiling inside the CRT
coupling could result in a leak or fracture. Glycerin
effectively stretches the thermal stability of the solution.
Distilled water and glycerin are available at nearly any
grocery store or pharmacy.
50% Distilled Water
50% Propylene Glycol
--
"EXPERIMENTAL FLUIDS"
Many frustrated repairmen have used such "experimental
fluids" in place of proper coolants as:
Mineral (Baby) Oil
Chlorine Bleach
Pure Water
70% Alcohol
and Zeus only knows what else.
None of these is acceptable, and their use will most likely
result in damage to the CRT phosphor due to excess heat,
chemical damage to the acrylic front lens, softening of
silicone sealant, corrosion of the aluminum coupling, fire,
explosion, or worse: a dim fuzzy picture.
If one wanted to be creative with one's coolant I would
suggest KY liquid or other "personal lubricants" with
similar primary ingredients. These, however, are generally
many times more expensive than the more conventional
formulations given in the previous section.
CONCLUSION:
Assuming success of the procedure one can expect the new
coolant to last at least the life of the CRT--which can be
further extended through the addition of fans and/or larger
heat-sinks. After CRT reinstallation the set will likely
require a convergence adjustment. It is also possible that
the previous or current owner may have abused the screen,
focus, convergence, brightness and picture controls in a
futile attempt to compensate for the symptoms of cloudy
coolant; These will need to be recalibrated.
NOTE:
These instructions may apply to similar televisors, but
to the author's knowledge are specific of the KPR line
from Sony. The author accepts no liability and provides
no warranty for the information contained in this
document.
June 2004,
Jonathan Moore Liles
----
There are two methods for changing the coolant fluid in
these CRTs. One is invasive and is akin to refurbishing. The
other is much less labor intensive but may be ineffective
depending on the stage and severity of corrosion inside the
CRT coupling.
Firstly, allow me to state the facts of the issue as I have
come to understand them through process of experiment and
investigation.
PROBLEM:
These CRTs have a partially painted aluminum casing such
that the aluminum surfaces inside the coolant reservoir are
in constant contact with the coolant.
The coolant used by Sony is a highly concentrated solution
of Ethylene Glycol.
Ethylene Glycol decomposes at temperatures around 187
degrees Celsius in the presence of oxygen and copper or
aluminum, degrading into five organic acids: glycolic,
glyoxylic, formic, carbonic, and oxalic. This process is
corrosive to copper and aluminum. The threshold for
decomposition is lowered with the boiling point of the
ethylene glycol solution. DECOMPOSED COOLANT IS WORTHLESS
AND SHOULD BE DISCARDED.
The end result being the corrosion of the aluminum reservoir
and the deposit of corrosive by-products (aluminum oxide?)
onto the glass of the CRT and convective divider, causing a
blur in one or more colors (tubes) and in all or part of the
screen area.
SOLUTION:
The only solution is to remove the spent coolant, clean
and/or repair the reservoir, and refill with virgin coolant.
Both of the following methods require the removal of the
affected tube(s) from the chassis. This is relatively
simple:
Remove the focusing rack (connected to the CRT coupling
by four screws)
Disconnect the high voltage anode leads from the red
splitter block by pushing in and turning 90 degrees. The
anode cups are permanently sealed to the CRTs and
removing the cup end is unnecessary and dangerous.
Discharge the tube to ground without electrocuting
yourself.
Disconnect the tube while leaving the yoke attached and
intact. This may require desoldering the 2-4 convergence
wires. Be sure to note the order as incorrect assembly
may damage the convergence circuitry.
Finally, remove the tube from the set.
THE HARD WAY:
Remove the two drain screws. Extract the spent coolant with
a syringe or pump (there should be slightly more than 6
ounces). With a 1 inch long razor, cut through the silicone
sealant between the CRT face and the lens assembly. This is
easier than many people think: Insert the blade until you
feel a release of pressure. Remove it. Advance the width of
the blade. Repeat over circumference.
Once the lens assembly and CRT have been separated, the
corrosion should be visible. Do not attempt to remove it by
scrubbing. Soak both halves in WHITE VINEGAR (a %5 acid) for
thirty minutes to an hour, agitating regularly (but don't
get the yoke wet). This should dissolve the deposits from
corrosion. Look carefully at the pitting. Can you see the
shine of bare aluminum at the bottom of the pit? If
not--continue soaking. Rinse with hot water one the
corrosion has been removed.
Scrape all of the old silicone sealant from the mating edges
of the assemblies.
Use painter's tape to tape off the glass face of the CRT and
the glass of the lens assembly. Be certain to tape over the
opening into the lens cavity (located between the acrylic
front lens and the convective glass divider)! At this point
you can safely polish the mating surfaces of the assemblies
with emery cloth or some other abrasive to give the silicone
sealant a suitable bonding area. Tape over the mating
surfaces, as they should not be painted. Paint both units
with FLAT BLACK ENAMEL spray paint (high-temp engine block
enamel works well). Be certain that no bare aluminum is
exposed on any inside surface. Let the paint dry for the
period recommended on the can (usually overnight).
Or, for a slightly quicker method, paint the inside cavity
by hand with quick drying BLACK ENAMEL PAINT (perhaps auto
touch-up paint, or model makers paint), which should dry
completely in thirty minutes to an hour.
Once the paint has dried remove the painter's tape and clean
the glass surfaces one last time with a solution of water
and alcohol OR ammonia.
Lay the lens assembly down so that the mating surface faces
up. Apply a quarter inch wide bead of GE Silicone II Black
RTV (non acid-cure) sealant . Gently lower the CRT mating
face until the two meet. Apply slight force. A small bead of
sealant will be displaced from the seam.
Let silicone cure for 24 hours.
Use a clean syringe to fill the reservoir with 6 ounces (180
CC's) of VIRGIN COOLANT. Leave a few bubbles at the top:
they relieve the pressure and keep the unit from leaking or
rupturing.
Reinstall both drain screws. Reinstall the CRT into the set.
THE EASY WAY:
Remove the two drain screws. Extract the spent coolant with
a syringe or pump (there should be slightly more than 6
ounces). Fill the reservoir with 6 ounces of WHITE VINEGAR
(a %5 acid). Reinstall the drain screws and allow unit to
sit for several hours (or overnight), agitating regularly.
This should dissolve the deposits of corrosion. Remove the
two drain screws. Extract and discard the spent vinegar.
Refill half-way with 3 ounces of hot water (preferably
distilled, de-ionized, or de-mineralized), agitate, drain,
and repeat.
If any products of corrosion remain in the reservoir they
will pollute the new coolant and result in more deposits on
the glass. The process of corrosion, however, should not
resume unless the coolant breaks down due to extremity of
heat or time.
Drain all water from the reservoir. The coolant will absorb
water from the atmosphere, so a few drops left in the
reservoir won't hurt.
Use a new syringe to fill the reservoir with VIRGIN COOLANT.
Leave a few bubbles at the top: they relieve the pressure
and keep the unit from leaking or rupturing.
Reinstall both drain screws. Reinstall the CRT into the set.
REPLACEMENT COOLANT:
There are several existing formulations of CRT coolant. One
may, of course, order some from the manufacturer, but one
must also be willing to pay a premium. The raw ingredients
of most CRT coolants vary little from such common items as
toothpaste, eye-drops, automobile antifreeze and KY liquid.
The following are formulations that I consider viable:
80% Propylene Glycol
20% Glycerol (glycerin)
This is the preferred formula, and is the most like those
provided by electronics supply houses. Propylene Glycol is
non-toxic and has better thermal durability characteristics
than the Ethylene Glycol found in commercial products.
Propylene Glycol is less likely to degrade or become
corrosive. It is also easier to acquire locally through
pharmacy, veterinary, and restaurant suppliers. Glycerin
is also widely available, however usually more expensive
than propylene and ethylene glycol.
60% Distilled Water
40% Glycerol
Water is a more effective thermal transfer medium than all
of the other chemicals mentioned in this document.
Unfortunately, it has a high freezing point and a low
boiling point relatively. Freezing or boiling inside the CRT
coupling could result in a leak or fracture. Glycerin
effectively stretches the thermal stability of the solution.
Distilled water and glycerin are available at nearly any
grocery store or pharmacy.
50% Distilled Water
50% Propylene Glycol
--
"EXPERIMENTAL FLUIDS"
Many frustrated repairmen have used such "experimental
fluids" in place of proper coolants as:
Mineral (Baby) Oil
Chlorine Bleach
Pure Water
70% Alcohol
and Zeus only knows what else.
None of these is acceptable, and their use will most likely
result in damage to the CRT phosphor due to excess heat,
chemical damage to the acrylic front lens, softening of
silicone sealant, corrosion of the aluminum coupling, fire,
explosion, or worse: a dim fuzzy picture.
If one wanted to be creative with one's coolant I would
suggest KY liquid or other "personal lubricants" with
similar primary ingredients. These, however, are generally
many times more expensive than the more conventional
formulations given in the previous section.
CONCLUSION:
Assuming success of the procedure one can expect the new
coolant to last at least the life of the CRT--which can be
further extended through the addition of fans and/or larger
heat-sinks. After CRT reinstallation the set will likely
require a convergence adjustment. It is also possible that
the previous or current owner may have abused the screen,
focus, convergence, brightness and picture controls in a
futile attempt to compensate for the symptoms of cloudy
coolant; These will need to be recalibrated.
