Marquee Modification Performance enhancement thread

I first saw this mod on the MMT and then went to Jeahong Lee's thread:
some way to improve PQ greatly in Marquee 9500
The reason for this mod is to remove the older noisy carbom composition resitors,
these are in the G2 signal and the resulst vary from projector to projector but there
is a reduction in background noiseespecially in lighter scenes. I also noted an increase
in shadow details.



Remove HVPS and open up unpotted section.
remove all the carbon comp resistors and replace with 2 watt ceramic ohmites of same value.
Also I changed the 4 large caps with polypropylene caps of same value. this doesn't have to
be done unless the caps are leaking or not close to rated value. Mine were fine but I did it anyhow.
What i am going to say next is only after you do this mod and have a problem with the other
tubes staying on when having only one tube on.

to test for the tube intensity anomaly as I call it:

After you put power supply back in turn on projector and bring up the grid. Now select one
color at a time by pressing color then 1(red) 2 (green) 3 (blue). Do one at a time starting
with red... look into the other tubes and see if you can see the grid displaying on another color .
A very very light grid is not too bad of a problem and wont show up on the screen.
However Some of use who have done this complete mod with caps and resistors have had it
where when one color is on the tother tube or tubes are also lit up to the point it can show
up on the screen. I and one other person have decide to measure the value of the resistor we
took out and replaced with the 560kohm ones. Mine were close to 680kohm, I thought that if i
increased the value of the ceramic resistor to that of the old drifted ones the anamoly might
go away, which it did. now I did not notice any ill effect so far with this increase. And if you don't
notice a problem with the projected image then leave the 560kohms in. It might only happen
with the cap changes not sure but post back your results here, I would like to find out if others
have noticed this as well. Mike Parker has not noticed this happening to the ones he has done
and suggested to me not to change the value, howwver it was way to bright and it was affecting
my picture. After the fix all is well after many hours of use.

Here are pics of the HVPS:










Leave room for resistors to breath !!







Part numbers for Ohmite Resistors

560K 2W OY564K 6
1K OY102K 3
220 2W OY221K 2
270K OX274K 2
470K OY474K 1

Caps:

www.newark.com/jsp/search/productdetail.jsp?SKU=18M2493

www.newark.com/jsp/search/productdetail.jsp?SKU=37M0653



EDIT: To keep the HVPS regulated better for the transients from Dark to Bright
with out blooming Chris Stevens added 4 125f 100 volt Wet tantalums to the 390 volt rail
coming into the HVPS. Well to find those caps cheap is not easy. So I came up with using A single HV Film Cap.

here it is on Justins HVPS.

Next we are going to replace 4 caps for each color for a total of 12. this I got from an old post By Chris Johnson and from the jeahong_lee thread were Mcpherv changed out some of the same caps that CJ changed. CJ's link is gone so i cant go back to explain what he wrote about this mod. From Mcpherv's comments the 6 1uf or 22uf caps ,depending on which board you have, couple the dynamic focus output and should be fairly important. I used 22uf caps to replace the older boards 1uf go with a higher voltage than 50 and low ESR like the panasonic FC series. I always do one section(color) at a time and test the board after each change incase I goof and something doesn't work it's a lot easier to track down a bad solder or backwards placed cap....having said that, on the newer boards caps C102,103,202,203,302,and 303 are marked for their polarity on the older boards they are not and I had to find out the polarity. the pics here are from the older board. so in this pic the positive side of the 22uf cap will go to the wider trace or the one farthest from the heat sink on the back of the board. And we will replace the 6 470uf 35v caps with 1000uf 35 or 50 v caps.These decouple the 24volt rails and half of the dynamic focus circuit. C108,208,308,107,207,307.

Removed caps 308 and 303




Caps 302,303,307,and 308 in place




close up




Now test the section you changed by ramping the focus up and down making sure it functions properly. If all is well do the other colors in the same manner.

Another section of the dynamic focus are coupled by C120,220, and 320. these are 2.2uf 250v caps . Replace with same value higher voltage caps of same type. I went with 305 volt.EDIT 11/17/2013:Wima Caps would be even better

removing cap




New cap in place



once again test after change this time you can test after all three are swapped out.

Next are the op amps u101,201 and 301 they will either be MC34074 or MC34084. these are noisy and distortive. Idealy I wanted to replace them with the OPA4134 but they no longer come in the DIP package so i found the TLE2074 which is less noisy and distortive. these can be gotten from Texas Instruments as free samples.

Now if you have a newer board you may not see the added diodes to the op amp as in my photos. I also decided to swap over the tech note diodes to the TLE2074's incase they do something else beside protect the op amp.

Op amp with Diodes





Removing Diode assembly from op amp




Now you need to remove the solder from underneath, i used the desoldering Iron, if you cant get it all out you will need to use some desoldering braid as well.

Underside of op amp section




After you remove as much of the solder as possible you may have to use a screwdriver or an exacto knive as i have to push any pins away from any remaining solder in the through holes.




Now is the hard part, you dont want to pull any of the through hole or traces out from the board so begin loosening the chip slowly from the board i use a flat screwdriver to wiggle it loose then a IC puller while wiggling it. you may have to use your free hand to touch your soldering iron to the underside of any stuck pin while holding the board vertically and pulling on the chip from the top side, this takes practice but if you have a vice to hold the board its much easier.

IC puller




then place new chip into through holes make sure all solder is out or it will be almost impossible to place new chip, I put one side in then use a very small flat head screw driver to push each pin towards its appropriate hole.

New chip in place




now if you have the resistor assembly replace that to chip.Be carfull when removing that chip you can see in this next pic where i melted a cap with the iron!!!!:shock:

replacing Diode assembly






Now solder from underneath and test after each op amp removal as stated before.

that completes the focus board.

Athanasios

I think doing this tread is harder than doing the actual upgrades!!!!!
I have a whole new respect for MP and his work, putting together that MMT
must have been a lot of work but this is sooo much fun too!

Athansios

Joust Said:


He's probably very busy with the Barco and G90 mods. I hope he dosen't ask me any
technical questions! I just found all this stuff and tried it out on my own. I have read
up on a lot of the stuff and am trying to learn . Sooo many people here and on AVS
have helped me in understanding how CRT's work and also the electronics involved.
This hobby has truly become an addiction for me and I LOVE IT!!!!

Athanasios

Joust Said:

Those traces go to the caps we replaced , through a resistor. I think its a 1 ohm resistor i dont have the board here
in front of me I have some color wheel inductors that i wanted to replace that resistor with. but none I have measured have a 1 ohm resistance the closest was a 100uh at .7ohm,s I dont think that would hurt anything being off by 3 tenths of an ohm.

Athanasios