CurtPalme.com Home Theater Forum

CxTurbo · Joined: 13 Oct 2008 Posts: 387 Location: Ontario, Canada

Ok, here goes.

I was in the process on replacing the visibly burt caps on my Video out and various other boards.
While I was at it I said "Screw it".I changed every damn one and cleaned all of the connectors with Deox-it. Figured I should be golden now.

Fired it up and all of the issues I had previously are now gone. Such as not syncing loosing sync etc. I now however have a new problem. The menu is shaper then ever and bright. the actual picture is dim and no matter how high I raise the contrast I can barely see the picture or test pattern in a completely dark room. When the menue come up it almost washes out the patters. It is damn near impossible to do a convergence on it. I do know that the Vido output board wire to the neck boards are prone to coming loose when work is done on that board so I checked them and they appear to be in place and seated properly.

I am looking for some help on what else I could check. I am at a loss here so far. I have taken the 3 boards ot again and will put them all back again after I check for bad caps/solder joints
for the 3rd time. LOL

I was also wondering if there is a possiblity if the greyscale adjustment on the video out board could be off do to different caps being installed. They are all high temp low esr. I however did not change the non-polar caps as I did not have them here and some of the 50v 1uf and the 63V caps on the defflection board were also not changed as they appeared fine. There is also no one tube that is appears more dimm than the other. It seems fairly even across them all.

Any thoughts?

CxTurbo · Joined: 13 Oct 2008 Posts: 387 Location: Ontario, Canada

Ok, more information to add now.

It looks like the grey scale settings on the video output board may have been affected by the capacitor change. When I select the built in white test patterns they are clearly grey. Also the vertical lines are much brighter then the horizontal lines I would say just above visible.
Am I correct in assuming this or should I look elsewhere? Also should that board be the issue is it able to be calibrated without have to send in the whole chassis or will I need to tackle the damn thing myself.

gjaky · Joined: 05 Jun 2010 Posts: 926 Location: Budapest, Hungary

You mentioned, that the picture (even the test pattern) is very dim then it is not a surprise if the white test pattern looks grey... (if the grey looks greenish, blueish, redish -that's the problem)
You wrote eariler that you have a lot of spare boards, try to swap them and you'll find which board affected with this dim issue (I suspect the video out board)

macgyver655 · Joined: 22 Aug 2007 Posts: 6954

Which boards did you change parts on?

I would double check and make sure you didn't put a cap in backwards.

CxTurbo · Joined: 13 Oct 2008 Posts: 387 Location: Ontario, Canada

I will swap out the output board and check my cap placement again and make sure I did not by mistake place a non-polar with a polar or incorrect value.

I changed caps on the Deflection, Video in and Video out boards.

I am going to look at the troubleshoot manual as well to see what I come up with.......

Time to invest in a scope if not...

**Curt Palme** · Posted: Wed Apr 20, 2011 2:16 pm Post subject:

UNless you have NEC extender boards for the video output board, a scope isn't going to help much. I've had similar problems in the past, both by incorrectly installing parts and by a recapped board now affecting other boards. I would do as gjaky says, swap boards from another set into this one and see if you can narrow it down.

macgyver655 · Joined: 22 Aug 2007 Posts: 6954

Is this a regular, plus or Extra?

That trouble shoot manual probably wont help anyways. I'm betin a backwards cap or broken trace.

CxTurbo · Joined: 13 Oct 2008 Posts: 387 Location: Ontario, Canada

Ok, so I looked over the output board and I found a bad capacitor that I over looked. I swapped it out and still the same issue with the dim picture on low light output in general.

So, I then took one of my 3 spare output boards and got no picture at all the test patterns were as normal and I had great light output. I then put the third board in and the picture is bright and the test patters look bright as well.

So the problem does appear to be in that board as suspected. With that being said does that mean that a calibration of that board is needed?

I looked over the service manual and could not find what components C3009 affects and if it by chance took out something else when it blew.
Or where in the circuit it is and if it would/could affect all three channels output.

Thanks for the help so far guys.

draganm · Joined: 08 Mar 2006 Posts: 5080 Location: Colorado

Replacing capacitors is not as easy as it looks. I spent 6 months slowly developing the process before even considering offering it as a service for marquee.
In your case I doubt it's a reversed cap, they will almost always blow instantly and trip the circuit. I suspect you put in wrong value somewhere. There's one on the MArquee vertical board which looks like a 22uf but if you look very close it's 2.2uf, big difference (factor of 10).
If you have a factory schematic or spare board check them all one by one for correct capacitance value and at least equal or slightly higher voltage rating.

**Curt Palme** · Posted: Wed Apr 20, 2011 5:59 pm Post subject:

Whatever you do, DO NOT touch the white balance controls. A properly working set will not require tweaking of trimpots, even if you've changed a bunch of parts on any board in the set.

CxTurbo · Joined: 13 Oct 2008 Posts: 387 Location: Ontario, Canada

Thanks guys.

Mac I have a 9PG or 9000.

Don't worry Curt I will not touch nor have I touched any of the pots on any of my boards. I headed the warnings in your information on the main pages. 8)

I am going to go through the board to see values and go from there. I know that there were some 4.7uF and 2.2uF caps so it is a possibility.

Thanks again guys.

macgyver655 · Joined: 22 Aug 2007 Posts: 6954

macgyver655 · Joined: 22 Aug 2007 Posts: 6954

CxTurbo · Joined: 13 Oct 2008 Posts: 387 Location: Ontario, Canada

Mac, the switch is in the "Norm" position.

I went through the cap values again and it appears that all is well with that no non-polars in polar positions or reversed polarity.

How many volts up can you go without causing an issue as long as the value is the same?

For example is it safe to go from say a 6.3V 100uF to 10V 100uF?

For my own curiosity what affect does changing the voltage have on the capacitor/circuit? Say if you went from 16V to 50V or even 10V to 63V or more. Other than the physical size difference what changes?

macgyver655 · Joined: 22 Aug 2007 Posts: 6954

Going to 10v from 6v is no problem.

I looked over the schematics of the video out board. I'm a little apprehensive on giving any info on troubleshooting projectors cause of Curt's business but I know he doesn't like repairing boards that others have messed with. So I'll give you a little info but if Curt emails me then you'll be on your own.

What you need to do now is test all the voltages going into that board. You may have a line being pulled down by something causing a drop in gain of all 3 video signals. Locating which voltage is abnormal is the first step in locating it. You have the schematics so the info is there.

Don't forget there are a couple regulators on the board that also will have to be checked for proper output.

CxTurbo · Joined: 13 Oct 2008 Posts: 387 Location: Ontario, Canada

Thanks Mac I will look over the schematics then test the appropriate voltages.

Do you have any input on my other questions?

I do not want to offend Curt either so I respect your reluctance. I honestly am not sure if I would have sent this board to him as I am just trying to learn something and waiting on getting my 8500LC going. I will more then likely sell off all of my NEC stuff once that happens.

macgyver655 · Joined: 22 Aug 2007 Posts: 6954

draganm · Joined: 08 Mar 2006 Posts: 5080 Location: Colorado

CxTurbo · Joined: 13 Oct 2008 Posts: 387 Location: Ontario, Canada

**Curt Palme** · Posted: Wed Apr 20, 2011 11:49 pm Post subject:

AS long as you're not under the rated voltage of the original cap, you're fine. you could put in a 450 volt cap and it would work fine. It probably wouldn't fit though. Smile

BTW, one option could be down the road is to send me the boards to simply test them. I agree, the amount of time spent on a board to recap it usually isn't worth it to send me the boards, esp on an NEC that you plan on selling, so no problems there. I just can't spend 3 hours and $40 in parts and charge $100-125 with return shipping, which at this point is all I could charge for a PG. Heck, I can't even sell used boards for NECs for cheap due to the failing caps. I know I have ONE working PG video board, the other three in stock need that 3 hours worth of work done to them. Sad