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Marquee Magnetics Alignment |
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We have had many inquiries into
the procedures needed for correct magnetics alignment
that typically follows replacing a CRT. We show this material
for the enlightenment of technicians who are experienced
with CRT projector servicing and who fully understand
the inherent risks, but who are not priorly familiar with
the Marquee chassis. Read the disclaimer very carefully:
The procedures being detailed
are hazardous for the untrained beginner; these procedures
involve handling vacuum tubes, with the inherent danger
of flying glass fragments if a tube is shattered, and
also involve reaching into a running projector chassis
with the possibility of high voltage discharging from
the tube body to the person performing alignments, as
well as other exposed metallic points carrying lethal
voltages. Any untrained individual contemplating these
procedures is advised to hire a skilled and experienced
technician instead. E-Tech Systems cannot be responsible
for injury or death for those attempting these alignments;
individuals not heeding this warning are proceeding at
their own risk. We insist that such individuals limit
their use of this information to a diagnostic purpose
only, to determine if a skilled technician needs to be
involved.
When displaying grid or
dot patterns the colors may be displayed singly (Push
COLOR, 1; COLOR, 2; COLOR, 3 for red, green or blue),
for pairs of colors push COLOR, 4; COLOR, 5; COLOR, 6;
and COLOR, 8 for all three colors. For purposes of clearer
photography, we have set loose parts on a table, and removed
most of the covers normally found on a Marquee projector.
Required tools are a 3mm ballnose allen driver, a medium
phillips screwdriver, a plastic 0.10" hex coil alignment
tool, and possibly a thin 2" knife and a small butane
torch. For scan yoke leveling, the projector must be displayed
on a screen.
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The Scan Yoke |
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All magnetics and procedures
across the Marquee platform are very similar save for
zone stig correction found on the M8500, M8500LC, M9000
and M9500LC, and the Ultra series. Passive stig correction
using magnet rings incorporated into the flare yoke is
to be found on the M8000 and M8110 and that procedure
differs. It seems logical to begin with the front-most
magnetic device on the tube neck, and this is the bell-shaped
scan yoke, a.k.a. the sweep yoke. (See Pic.
1) Extreme care must be taken when pulling a scan
yoke from a spent tube for re-use; these were often secured
to the tube glass with large amounts of hot-melt glue
during assembly of the projector; the copper windings
inside the yoke bell are totally exposed and easily ruined
if nicked or disturbed in any way. (See Pic.
2) A long thin knife heated by butane torch can be
employed to slice into the glue found between the scan
yoke and the tube glass (See Pic.
3); be aware that hot glue can be flammable and we
advise doing this on a metal surface with a fire extinguisher
at the ready. Even with experience, a heavily glued yoke
can be ruined in this procedure; we lose one yoke in ten
due to nicked windings. The scan yoke needs to be as far
forward on the tube neck as possible for best alignment
of the other yokes behind it; we advise removing any excess
hot glue found on the windings; the heated knife blade
is effective when used with great care not to disturb
the windings. The alignment of the scan yoke is limited
to rotating it to square the raster to the tube face (See
Pics
4 & 5).
We have removed the lens barrel for photographic purposes,
one can usually see adequately by just looking into the
lens.
Do not
come into contact with the solder points on the yoke for
the red/white/blue horizontal yoke wires or the exposed
copper windings anywhere on the scan yoke; they carry
pulses over 1000 volts! Do not contact the yellow tape,
there are windings just under the tape. The scan yoke
can be turned by gently pulling on the yoke wires.
Null all skew and convergence
corrections* before setting the horizon (the horizontal
line of the test grid that is half way between top and
bottom) to be level to the edges of the tube phosphor.
Pic. 4 is not so good, Pic. 5 shows correct rotation of
the scan yoke. A yoke not leveled properly will require
unnecessary use of skew and convergence corrections that
may lead to the convergence amp running hot, and drifting
of convergence. If changing all three tubes, start with
green and level it first; then level red and blue horizons
to the green horizon rather than the tube phosphor; this
will give best results and minimum drift. To secure the
scan yoke against unwanted movement, one can apply hot-melt
glue to the gap between yoke and tube glass; or consider
gluing the scan yoke rear edge to the front edge of the
convergence yoke behind it, but not until the convergence
yoke is leveled also. The convergence yoke features a
clamp, sufficient to secure both. |
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The Convergence
Yoke |
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The convergence yoke (See Pic.
6) seen loose is mounted immediately behind the scan
yoke (See Pic.
7), and must also be leveled so that corrections applied
by it are not vectored improperly (See Pic.
8) but are applied in the required up/down direction.
Use a zone that is not in the center, as static convergence
is delivered through the deflection system. Green convergence
is accessed at CONV, 5, 0901, 2. The convergence yoke
would be turned clockwise a bit to correct this vectoring.
(See Pic.
9). Care must be taken to relevel the scan yoke if
leveling the convergence yoke has caused the scan yoke
to turn. The harness feeding the convergence yoke carries
no major voltages and is safe to touch. When all is right,
the convergence yoke clamp can be tightened using a 3mm
ballnose allen driver, and some hot-glue can be applied.
(See Pic.
10) The rear edge of the scan yoke is keyed to fit
into the front edge of the convergence yoke so they stay
near the correct angles of rotation to each other and
this fit is needed for the convergence yoke to properly
be as far forward as it can go on the tube glass.
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The Focus Yoke |
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The focus yoke (See Pic.
11) is a large device with brass fittings at the rear
and wires exiting the bottom rear; it contains driveable
windings for focus correction and, on most models, windings
for zone stigmation (dot shape) correction also. Powerful
cylindrical permanant magnets are also housed within.
(See Pic.
12) The focus yoke is secured to the tube glass by
two clamps employing 3mm allen screws, one at the very
rear, and a second clamp accessed through a small hole
in the yoke housing. Hot glue is often found at the front
of the focus yoke holding it to the convergence yoke,
and also along the rim at the outside rear; this glue
must be chipped away for alignments to be performed. One
does not rotate the focus yoke except to orient the wires
near the bottom and the brass fittings, usually wingnuts
and screws, so they are within reach and can be tightened
from the top. The focus yoke installs behind the convergence
yoke with a 1mm gap, just enough to allow up/down and
side/side movement for alignments. The opening through
the center of the focus yoke is larger than the tube glass
by several millimeters, (See Pic.
13) thus allow-ing, with the brass fittings loosened,
for the focus yoke to be moved up/down or side/side relative
to the tube glass; this allows for raster centering and
also gives a crude flare adjustment that is fine-tuned
after by the rings of the flare yoke. Make sure no edge
blanking is in effect that prevents you seeing the true
raster edges. Push keypad button "*" three times to read
out blanking values, they need to be all at zero. After
alignments are complete, the brass fittings should be
tightened well and hot glue can be re-applied to secure
it, where possible. This may not be practical on a ceiling.
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The Flare Yoke |
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This is a smaller device just
behind the focus yoke (See Pic.
14), secured by a clamp and a medium phillips screw;
and can be found in three variations. All have flare adjust
rings in the forward position, adjusted by a small thumbwheel.
One adjusts flare by inputting a 31khz non-interlaced
signal to the Marquee, or selecting 31khz from the Internal
Frequencies at UTIL, 1, 6, 2 One then pushes # for Dots
Only, then throw user focus (push PIC, 4) to zero, and
Contrast to 80 or 90 such that a fuzzy patch is visible
at each dot, with a hot spot visible in the fuzz. (See
Pic.
15), flare not set correctly. After picking away any
hot glue or silicone on the flare yoke rings, one then
swings the flare rings adjusting knob at angles to the
tube axis or twirls the knob as needed to center the hot
spot in the fuzz. (See Pic.
16) This may throw off raster centering and require
repositioning the focus yoke, as these interact with each
other.
If dot
shape is stretched too oval then it may be necessary to
rough in the stig adjustments for dots to be more round,
so flare can be done correctly.
Do not forget to reduce contrast when finished and also
remember that new phosphor is more easily burned by test
patterns left up too long or driven hard. Do not leave
dot or grid patterns up for more than a minute at a time
at high contrast levels.
Flare yokes for M8000 and M8110 also incorporate passive
stig correction rings; these are aligned by displaying
31khz dots and shoving user focus to 100 and contrast
to 80-90, then setting the rings for round dots in the
center of the raster. For M8500, M8500LC, M9000LC and
M9500LC the adjustments are found in the Service Menu
and are adjusted by zones from the keypad. See Below.
This allows for setting dot shape on the corners and edges
separately from the center, for more uniform focus across
the raster. Some M8110s and newer Ultras are found to
also have a third pair of rings called 6-pole magnets
(See Pic.
17); they are adjusted like stig but are used to correct
triangular dot shapes if present. |
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Other Related
Adjustments |
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It is also desirable to match
raster widths and raster heights as to impose the least
work load onto the convergence section. Raster heights
of red and blue can be matched to green in the Service
Menu under UTIL, 9, 0901, and 3; use the on-screen prompts
and arrow keys to match red and blue heights to green
at the mid-screen point, looking only at the top and bottom
edges.
The Marquee chassis employs a two-stage horizontal scan
system and dual windings in each scan yoke; at frequencies
below 59.5khz the yokes are operated in Series and generate
sufficient width for that range. Above 59.5khz the HDM
switches the yokes into Parallel mode and more current
can then be provided for the higher scan rates, thus necessitating
two separate but similar alignment procedures for width
matching.
Width matching is done to the Horizontal Deflection Module
(See Pic.
18) with a 0.10" plastic coil alignment tool; NEVER
attempt this with metallic tools, the coil carries pulses
over 1000 volts. With a 31khz signal displayed and all
convergence nulled*, determine which colors are too narrow
at the mid-point of half-way up the raster, and back out
the low-band slug a few turns for that color. See Pic.
19 to determine which coil does what. If a color is
too wide, turn that low-band slug in towards the windings
on the coil. If they cannot be matched then a scan yoke
may be not be as far forward on the tube glass as possible
due to hot glue inside it. After completing low-band width
matching, display a signal of 62khz or higher and similarly
match the widths but by adjusting the high-band slugs.
Zone stig adjustment can be done after the projector is
reassembled. Display 31khz dots with user focus at 90
and then enter the Service Menu, UTIL, 9, 0901, 7, raise
contrast to 80-90 and use the keypad arrow keys to set
oval dots (See Pic.
20) until they are round at all points in the raster
(See Pic.
21). Reduce the contrast level before exiting the
routine, and reset user focus to 50. One can also set
the six-pole magnets found on the flare yoke now, if covers
are left off.
*Convergence may be nulled by selecting an unused Recall
Memory and then selecting UTIL, 1, and Clear Current Setup
(5), then adjust only height, width, keystone and pincushions
to suit.
This concludes our review of Marquee Magnetics Alignment;
these procedures would be followed by the usual zone focus,
raster squaring and other procedures of basic setup.
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Tim at E-Tech Systems Phoenix |
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