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home>>Tech tips>>Tech tip #9
Marquee Magnetics Alignment
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
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
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.
The Focus Yoke
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
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
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.
Tim at E-Tech Systems Phoenix
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