CurtPalme.com Home Theater Forum

[MikeEby]

[Nashou66]

it would be cool if your company did the Marquee boards Mike, but no bashing other members in my thread ! lol hehe ok back to buisness.

I changed out the Dac 8840 from an old 2006 Vim that i could never get working. Well the chip works fine now and i get Brightness adjustment for the Green, now
i have to fix the green Video cable as it must have broke while i removed it. Who makes your cables also Scott ? same comapny cause o only removed the board three times and it breaks? I have removed the marquee cables on my old 8500 at hundreds of time's and not one ever broke. Two thing gone bad on One PJ.. i wonder if this was put together on a monday .

Athanasios

[Nashou66]

Ok something is not right now, i get no green video. i thought it was the cable but a different cable wont work either. I Just realized that when i connected the red video cable to the green mini rca it would feed the video to the red but by ramping the brightness its the red signals bright that was moving the bright doesn't move with the RCA cable.!!!Doh!! So now I have no green video. I am sure the DAC was bad as I had green video but not bright adjustment. I lost green video somewhere before that I think.
Arrgggg!!!!!

While I was typing this i decided to go down and look again. If i wiggled the green cable i would get the green line on the right edge... ok some video. I wiggled more and i go a slight faint slice of pie shaped video in the green channel from left to right with the point of the pie starting on the left and fanning out to the right and the green line was also there. So i pulled the cable and touched the center pin to the end of R132 as this goes to the video pin i got the fanned image again but not as defined until i touched the ground part of the cable to the ground side of the RCA, and the fan was defined. I tried this same thing with the red and i got the weird shape if no ground was connected but when it was it was fine. i touched the red center to ground and got a weird image. So I thought hmm the video and ground are touching on the green. possibly in the RCA.
So I removed that and put a different RCA in. Same thing, I needed to giggle the cable to get the faint line and faint pie shaped video. The faint line made me think of the 1.5 meg resistor mod. I inspected the mod and the trace that needed to be cut i think may be pushing down to the ground plane on the Board. Scott could this be the Issue? I think moving the board in and out the slight bending of the board may have made the trace that was cut touch the Ground plane? How many Layer board is this? Its really frustrating now as I had it working then when i finally put the green cable back I lost green video.

And to boot my heater isnt working and its 30 degrees outside !!!!

Arrgg again!!!

Athanasios

[wkosmann]

Dear Athanasios;

I would have sent this as a PM to you, but your PM box is always full.

I have 2 extra sets of JBJR hand-made Belden mini-video cables, designed to run from the neckboards to the VIM on Marquee projectors. These are much heavier duty than the stock video cables. They are capable of being taken off either the neckboards or the VIM many times at each end. They also provide superior performance at 1080P, as an additional benefit.

I have 2 sets installed in my matched blended pair of Marquee 9500LC Ultras. For nearly 2 years these cables have been disconnected and reconnected, although not much recently.

Let me know if you're interested.

William

[Nashou66]

I actually have a bunch of that wire here and the connectors to make my own but thanks for the offer William. I also have more room in my inbox now. I cleared it last time you scolded me.

Its not the cable its something on the VIM now. It must have been there waiting to happen as when I first got this one up and running i had no red video but a quick solder to the center pin socket fixed it. So when the green went out i thought to look at that as well. It seams this Board was not made that well from the trouble I am having with it . the other VIM is fine and looking at the build quality it looks much nicer. I did measure all the test pints for the Bright signal to the VNB's and they are no ok, same as the working VIM. But no video, unless i wiggle the cable no matter what cable i use. I even removed the MINI rca socket and put a different one in and still the same. I measured voltages at different points along the video path and they are all similar going right up to the last resistor before the signal. Like i said in a previous post if I touch the video pin to the end of that resistor i get the same video image as if i did that at the resistors for each individual color. Now when i touch the outer ground of the RCA Plug to the outer ground of the RCA socket on the red the image is fine when I move it to the Green socket it stays distorted and i get the line on the edge. its something with the green ground plane , I still think its in the PCB Board. If so the board is shot . Hopefully Scott might have some other insight, i will pull the scope out tonight to measure the same points.

Athanasios

[Nashou66]

Here is a pic of what its doing, I enhanced it in iPhoto to so you can see what its doing. It is definitely a short of the video to ground , if i touch the red video cables pin to the outer part(ground) of the connector i get the same image.

Now i need to some how find the short , but I think its in the PCB I tried shining a bright light through that section but can't really see anything. Scott what should I do!!!! can I swap over the mods to another 02p board if it shot? this Sucks!!!

edit: this pic is when I am only touching the video to the center pin if i make a full contact the video goes out completely.

[mp20748]

[Nashou66]

Ok getting closer!!! So I am thinking the short must be in the video socket somewhere. So i decided to lift the end of the 24.3 ohm R132(pic attached) that goes to the center pin of the video socket, this would put the short out of the equation and if i touch the center pin of the cable to the lifted end of the resistor i should get video. Well nope I got the same distorted image as before. Damn!!! So now I touched the video center pin to other areas on the video path as i did before lifting to see what would happen and find where there might be a problem if my theory of the short in the socket was correct.
So i touched the pin before R132, same, i moved to pin 5 of AD835, same, then i moved to the green input solder spot to AD835 that goes to pin 1 on that chip BINGO!! Video!!! So now i think its the AD835 chip my have been shorted out
when the socket shorted from the older socket. I think that socket is ok since i am getting no continuity between the center pin and the outer Ground. On the old socket i must have shorted to ground just enough to possibly send a short to the AD835 chip and blow it( I think its blown). So now what do i do? this is where I need advice as these chips are 34 bucks. do i remove the possible bad chip and put it on a known working board to test, if its bad should i put the good chip on this board even though i am not to sure about having fixed the short in the socket area or if was even the socket that was causing the issue. it may have been the octal dac , but i can't see if its in the same circuit for sure.

Well I am getting closer none the less.

Just read your post mike while i was typing this.. I beat you to it i too did not think it was in the PCB I have not heard of that ever with low voltages.

EDIT: Mike would those 1.5 meg's cause the AD835 to go bad if not installed correctly?

[tse]

If the center conductor of the video cable shorts to the ground braid or the connector shorts the center conductor to ground it usually poofs the AD835. Sucks, cause they are expensive. Scavage one from a scrap focus-geo bd or VIM. Should come off pretty easy with the hot air desoldering system. Check the cable and connector for shorts before you put a new part on.

Scott

[Nashou66]

[mp20748]

[macgyver655]

[J Kildare]

[Nashou66]

Mcguyv, oops i was thinking of the AD834 on the 03p Vim's those are higher I think.

Athanasios

[Nashou66]

Well I checked the cable and the socket for no continuity before putting the AD835 from the good older board to the new bad board. Same thing!!
So I put the AD835 from the new board to the older board just to make sure it wasn't the chip. now that board is bad too, so I know the AD835 is going bad on the
new board...... but Why? I should have checked the power supply to it but didn't. SCott that is one thing you taught me before, and I always forget CHECK POWER TO BOARDS OR CHIPS FIRST!! So i'll check that tomorrow. if anyone can think of something else to look at let me know. I am getting very frustrated, I should just send the board to you Scott.

Athanasios

[macgyver655]

AHHHHHHHHHHH, see. This stuff is fun until you get a problem that is frustrating. well sometimes its still fun. Anyways, I dont think anybody can tell just what part to replace without looking further. yes you need to check voltage but I doubt you lost the supply because the red and blue still work so you need to look past R53 at pin 6 of U20. And dont forget gnd has R87 so verify gnd also at pin 3. If your voltages are good then you have to back track. If you want stuff thrown at you then, U8, U21 and surrounding circuitry. But why not just fire up that scope and use it. you have an advantage in this type of circuit where you dont even need to know specific patterns because you have working channels to test against. Just pick a point on the green channel you want to check, scope that point on the red or blue first and then look for that pattern on the green channel. You really have a fairly simple channel here. But your learning ability is good so I'm sure you'll find it.

[1031]

Athanasios, measure what it contrast control voltage to that green AD835 chip. If it is negative, then there is protection going on..Also test this: Start projector, when you got picture to tubes rapidly turn it off and on again. I have seen this thing happening with one of my vims. Turning it on again brings all tubes back to game, i never have looked what is culprit to that..But when contrast controll was negative AD835 had low/faint negative output. If that is case, then test if removing those variable caps+ resistors helps.

[Nashou66]

Yeah this is frustrating since it was only one issue no green brightness control.

Here is a run down on what I did.

1)Replaced D15 as I thought it was bad.
2) Replaced op amp U9
3) finally realized the voltage was not moving from the Octal Dac for the Green Brightness and replaced that, checked the voltage it worked at the test point
i did not have video connected at this point.
4) Connected video and nothing... note before this i did have an intermittent video going in and out as I touched the green cable i thought it was bad cable

So now yes McG. the scope is coming out.

Jarmo, I was also thinking the G-contrast but not negative I was thinking it is what maybe blew the AD835. I also want to remove the one now and see if works on the other board since the new boards ad835 i know is not working on the old board. So I am going to put back the old boards chip back i its original home and see if that board works. then I'll know for sure something on the new board is blowing the AD835.

Does this sound like a plan of action? no need to keep thinking its a ground short issue if the old chip works back in it original board i can then be certain the ground at the socket is ok and nothing else is blowing the chip, but if the old chip is bad on the old board also then I know to look for something blowing the chips.

So i am going to go swap out chips back again.

Athanasios

[Nashou66]

SOLVED!!!!

Ok I decided to first measure the contrast as Jarmo suggested and I planed on doing also while thinking about it all
last night while trying to sleep. he was right it was Negative voltage. so i looked at the schematics for the amp that outputs
contrast tot he AD835. U8 pin 7 negative so i went back to the next op amp that feeds U8 which is U9 pin 1 when i touched that pin the green grid came up!!! i did not solder the pin well when i replaced the chip the first time i was looking for the issue. That is why when i was pushing on the green socket it was intermittent coming in and out, the last push must have flexed the board enough to break the weak solder joint and cause it loose complete contact.

So i checked all controls and it all works. AD835 is still bad and must have been shorted some how since it doesn't work on my other board... Hmm I bettter check the solder job on that chip too now

Athanasios

[macgyver655]

See. Now that wasn't that difficult, was it.