Electrohome Performance
Modifications
If you think your projector
looks good now .......
The mod's below are a combination of modifications
we have designed for the new Crystal View line of CRT projectors and have
acquired from our purchase of Madrigal Imaging and the Vidikron CRT projector
line. This will be the first time we are offering our mod's for direct sale.
Please give us a call at 508-881-1613 to get more details and current pricing
and delivery information. We can recommend a package of mod's to meet your
requirements and budget. All of our mod's come with a two year limited warranty.
If you prefer to send us your projector and have us install the modifications,
we will do so at a reduced labor rate.
We also offer an upgrade of your existing
8" Marquee projector, LC or not, to a 9500LC for only $6500. This includes
new tubes, lenses, replacement tube mounting hardware, neck board upgrades
and calibration.
If the heading below is
underlined, it is a link that you may click on to see a white paper about
that modification.
Why Modify... (Click
Here)
Low
Voltage power supply
We have redesigned the voltage regulator circuit for improved stability and
lower output noise. The cooling system has been completely redesigned, with
a larger, slower fan and custom fabricated plenum for extremely low noise. This
is the quietest LVPS in the industry, by several dB. You can click on the underlined
heading to see a more detailed description of the LVPS mod.
High
Voltage Power Supply:
This mod adds a number of high-voltage tantalum capacitors
to the filter section in order to reduce the G1 voltage noise level (based on
a Chris Stevens design).
Convergence:
A number of capacitors are replaced on this board, with either low ESR, or low
internal impedance types, based on their specific function. As a result, the
convergence stabilizes faster, is less temperature dependent, and drifts far
less over time.
Neck Board:
This mod incorporates a number of changes to lower
the video noise, sharpen the image, and stabilize black level. The video amplifier
stage uses a new, higher bandwidth, faster settling op-amp with improved power
supply noise rejection. Ancillary chips are changed to types that provide
a more stable and lower noise black level. The video amplifier section is
also shielded from the heater current path to further reduce video noise.
High-Q film capacitors are added to supplement the surface mounted chips for
better filtering of the video amplifier power supply rail.
Deflection
Processor:
Through years of repair work on Marquees we have found that the Microprocessor
board is susceptible to damage from power supply rail transients. This can cause
many strange, minor malfunctions and some major ones. The modifications include
better input filtering and transient protection of the power supply rails. The
Microprocessor is also replaced with a newer, more reliable chip and the software
is updated to the latest version. The new IC and the software version are compatible
with all older software Revisions.
Vertical Deflection:
This mod replaces all op-amps with low-noise equivalents
and installs new filter capacitors to reduce noise and tighten the spot size
(deflection noise modulates the spot position; effectively elongating it). The
sizing circuit is modified to optimize the vertical size range for wide-screen
formats.
Horizontal:
The deflection circuit is modified to allow a wider sweep -
from the left to right edges of the tube faces, in order to increase the optical
resolution of the projector. The original deflection circuit design will handle
a very wide range of sync pulse widths and retrace times, in order to be compatible
with all kinds of sources. As a result, the unmodified, maximum image width,
especially at the higher sweep and refresh rates, is limited to much less than
the full width of the tube face. Since the tube face is round, one can also
use a slightly wider sweep width with a 16:9 than a 4:3 screen. The filter capacitors
on the input power supply rails are also replaced for lower noise in the deflection
output and thus a tighter spot size.
Focus:
There are two major sections to this module: The static focus section supplies
DC current to the focus coil to control the central spot size. The dynamic
focus section, which rapidly modulates the focus coil current as a function
of beam position - responding to functions related to the horizontal and vertical
sweeps plus zone adjustments - to maintain minimum spot size over the entire
face of the CRT.
In the static focus section, the voltage reference for the DAC, which converts
the digital focus setting to an analog control voltage, has been redesigned
for higher stability and better line regulation to the DAC. This better maintains
each CRT’s beam spot size against the effects of noise, temperature
and time.
In the dynamic focus section, the DC rail filtering has been completely redesigned
to minimize broadband noise and ripple on the voltages supplied to the focus
coil current amplifiers. This along, with changing all ancillary filter capacitors,
minimizes any noise riding on the dynamic focus coils, which would translate
to blurring of the beam spot.
Stigmator Module:
This board modifies the shape of the focused beam-spot and thus its apparent
size horizontally and/or vertically. Therefore low noise levels are as important
here as on the focus board. Mods to this board include replacing all of the
electrolytic power supply rail capacitors with low ESR types and adding film
capacitors to improve high frequency filtering.
Video Input Module:
The VIM mod incorporates a redesigned video signal path, which includes filtering,
coupling and bypass filters. New higher performance Op amps are installed, which
outperform even the CLC449 op amp. Improvements include higher bandwidth, and
lower input noise. When compared to a standard Ultra 9500LC VIM board, the image
from our modified board yielded deeper, richer colors, and sharper edge detail.
The improvements were even more striking when earlier versions of the VIM were
modified. The differences were most noticeable with uncompressed HD material
from our Laboratory D-5 deck using both 1080i and 720P formats.
C-Element:
All stock Marquee projectors, with the exception of some 8500LC/9500LC’s
have only color corrected lenses. To maximize their light output, MEC mixes
a small amount of yellow into the green and red phosphors of their tubes. The
down side to this is a more limited reproduction of color extremes, versus the
CIE color chart. This can be corrected by blocking the yellow output of the
red and green tubes with color filters inserted into the lens assembly, yielding
more accurate, deeper and richer colors. These filters can only be inserted
into LC type lenses. Non-LC lenses must be replaced to achieve this benefit.
Contrary to popular belief, the light output drop from adding these color filters
to the lenses is less then 6%. We have had nothing but positive feedback from
our clients on this modification. Most of our repeat clients insist on having
them installed on their new projectors, or when their projectors come in for
service or other modifications.
