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Discussion Starter · #1 ·
Guys,

Im needing to post on this because Im finding to many repairs coming in with blown horiz outputs transistors, and C-F drives.


1280 x 720P 16:9 setting is causing a problem with people running the expanded raster / short throw, Im not totally against this if used within reason, it does have benefits but it also has its downsides running out of spec.


If you have a choice use a couple extra inches of throw and save the repair costs. New drives are getting harder to find and replacing STKs is time consuming not to mention heating the F drive next to it.


Im not sure how many of you are noticing it but Im finding a S-curve showing up on these also, the internal test pattern will look ok but the image and external test pattern will show it as a distorted line top to bottom over exaggeration of {sss} by lowering the amplitude it decreases to a usable normal image.


I have tried to isolate the problem and its deflection related to tempurature, swapped in a brand new deflection board with the same results (expanded H width) getting worse after a few minutes with no corrections being done in convergence or focus.


If you make corrections in convergence for this it will heat the drive and lead to failure sooner or later.


Back when these were made the main freq used then was 640X480- 800X600-1024 vesa at 72 hz and where the breaks were made for default blocks, we had a service bulliten come out that related to H positioning 'rolloff' that could hit on either side of the 'hump' and result in H position being off to one side or the other depending on what signal you were switching from.


If you have the position problem its a easy fix of adding a 82K ohm resistor to R5031 (off pin 48 of MPC1880)


I mention this because a expanded raster can be 'thrown' against the side of the tube if memory or set up cant hold it off.


This was addressed on the Extra series PG6-9200 with the addition of DC H Linearity in the factory mode and related to Linearity and Linarity balance corrections to correct S curve.


Im just thowing some of this out there for thought when using this resolution, if you have a settings choice try 60 hz at neg neg sync but dont use the data copy. Save the parts please, Im about out again. Doug


Spec:

H width pot voltage at pin 2 of the PA connector is 1.8V using the video input at max amplitude. There is a 10% plus or minus so if your short a inch or two it can be brought up to fill the screen depending on screen size.


Quick observation to correct S curve:

Switch to 1080I if your in a pinch for time so you can sort it out
 

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thank u, thank u, thank u


i have had this problem on my RUNCO IDP 980 Ultra ( NEC 9PG Extra) ever since i purchased it second hand about 4 years ago. When a test pattern was seen there was a S shaped curve on the vertical lines. Started at the top initially then as the projector warmed up the curve descended down the picture. Internal test pattern was good and straight , convergence spot on.


to make the picture watchable ( ie reducing as much as possible the S deflection ) , we had to do converge correcting for the abnormality. now this was 4 years ago. running on 720p by the way


we tracked down the problem to deflector board but knew there must be something else. we were going to change the deflector board totally by buying another one from RUNCO. now i glad i didn't


i have been diligently watching this forum for years looking for this problem. posted it about 2 years ago - no luck


can u repair it for me !


jasmine
 

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Discussion Starter · #3 ·
Jasmine,

On this model you might try going into DC H Linearity from the factory mode and adjust it for least amount of s curve first. This will change a few things like linearity balance and pincushion. Write the setting down so you can set back. Remember you over corrected it already.


Id need to know the info from the information menu (hit info button) both freq and sync polarity. Send me your specs with throw distance screen width. [email protected]


This does sound exactly as I described, the curve actually moves with the temp changes and a straight internal test pattern. Doug
 

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Doug, I assume you mean a NTSC video source?


Checking mine right now....


And why Neg, Neg sync?
 

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Doug,

Anyway to post a picture of this? I've run my NEC 6PG Xtra at [email protected]

for awhile (I believe w/o a problem) but lately at [email protected] I have noticed my image 'curving alittle to the right' along the sides that seem to correct itself when the pj warms up. The internal test patterns looks good. Didn't really start seeing something until I purchased a HD receiver and was watching an upconverted OTA ABC HD show (native signal is 720)where they put black bars on the sides of a 4:3 picture...


thanks,

jidelite
 

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Ok I just checked my 6200.


With NTSC video, H-amplitude at max, I am bang on 1.80v. I did not expect this, as I tweaked the h-width pot *very* slightly to get my width.


It is 5.51v at 1280x720p at 75hz. The porches are tweaked in powerstrip to fill my screen at my throw ratio of 1:1.30.


The video image at MAX is a few inches wider than my normal image (as you would expect). I think I am ok.


Mark


PS. I also have fitted a large heatsink on the bottom plate over the STK chips. And a thermometer to the Def heatsink right at the H-out transistor - hottest I've seen it is 55 deg C, it's 47 deg C now, but ambient is only 18deg C.
 

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so - if you set up your PG at the factory specified throw distance this should not be a problem, correct?


thanks-
 

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Doug,

Does this apply also to the XG series?


I'm guilty as charged on using the horizontal width control. I had no test pattern problems with 2 PG 6+,s but never had any breakdowns due to over use of the width control, used 95 I believe at the time.


I'm currently using a XG135lc set at 99 width (cringe) with a Momitsu V880 set for 720p/60hz and the player has a narrower width already set within the player (about a 1 1/2" narrower on each side of a 16/9 92" wide screen)

The raster width on the tube face is well inside the tube border and I don't have any internal / external test pattern problems (straight lines)


My question is If your maxed out (pj) but the width is less internally at the source (dvd player) do you get a break here on reliablility or must you absolutely never go that far with the width control no matter what?


#2

Do the contrast and brightness have any effect on the horizontal width or related in any way to each other on this issue and is using a high gain screen (to reduce cont/brght) beneficial in this configuration.


I'd hate to pull back and redue, but if that 's what it takes to keep it healty then so be it. I'm hoping the scenario I've mentioned allows me to leave it alone BTW


So does that NEG NEG synch apply to the 720p/60hz you mentioned or the other older scan rates on the PG or XG also.


I appreciate your knowledge and time on the NEC series and info like this is good as gold and sure to keep the breed alive for a long time to come.


David
 

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Discussion Starter · #9 ·
Guys,

Video can be rgb also at 15.75 kHz if you dont have a video card.


I havent seen a problem so far set at factory spec but I have been asking for the resolutions on each repair and how I found the pattern developing.



Neg neg sync seems a likable match to the projector, if I have a choice I use it. Some irregularity's do show up from different sync. In some cases if the signal was entered using a different polarity it will give you the 'unregistered signal' display and use default.


There will be a difference between cold and warmed up, this is normal.


Im not trying to send an alarm but I do want to convey what Im finding when repairs go up over normal. I have seen this before when new processors come out, it has a pattern usually related to resolution and throw spec. On some they have a weird porch setting Doug


I havent noticed it in the XG but the H width is global for all signals and also measured using the video input. Different voltage at pin 1 IC5306 4.5V and there are two test points and two VRs the other is TP5302+ VR5302 7.5V
 

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Doug,

should we add the 82 ohm seriell or parallel to the 12 kohm R5031??? My setting: 1920 x 1152 @ 50 Hz with PAL, I can't see a curved line, should I see it with a better test pattern than the NOKIA or Philips Test Pattern Generator?

What effect has the resistor to the 1880?

Thank you,

Daniel
 

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Discussion Starter · #11 ·
Daniel,

If you are not having a position problem after switching from a higher or lower freq you dont need to do the mod.


The resistor hooks in parallel and changes the timing off of the 'hump'


The projectors H deflection circuit is 'bracketed' at certain fixed points along the horizonal freq range. Each of the brackets have unique factory preset geometric functions including horizontal position. Some of the vesa 72 hz modes sit directly on top of the bracket.


I see this most at 40 kHz range at 70 hz range. If you dont see the s curve in the image or external cross hatch then your ok. Sort of a two fold problem but notice they relate to each other, if you have the shift problem you usually have the s curve as well.


You need to re enter the signals if you do this though.


Im working on another deflection 'fix' for s curve specific to 1280 720P at 44 kHz, it should be a 'tack on' but pretty busy now just before Superbowl.

Doug
 

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Doug, I reported this problem with the PG's a long time ago and everyone, including you, thought I was nuts or was doing something wrong. Most swore that 720P was perfect on their PG's. I reinitialized and got rid of half of the line distortion but could never eliminate it. As a result, I gave up on 720P. It's 1024X768 for me. A few months later about six other forum members started reporting the same thing.


Chip
 

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Discussion Starter · #13 ·
Chip,

Yes I do remember that. Are you using 16:9 or 4:3 format screen?


It doesnt seem to affect all PGs and I have set many up using that specific resolution with great results. I do see video cards now and DVD players with weird porch settings and could also be contributing to it.


Most failure problems that I see is with the expanded raster, Jasmines Runco throw was ok and why I think his lasted.


The thing that ticks me off is I remember correcting it years ago but cant remember what I did for that application. Doug
 

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Doug,

It's on a 16:9 screen. I even moved the projector back with no decrease in line distortion. It was suggested to me that the problem may be in the wave or system board but as I had none for trial I just gave up. In my case the internal test patterns for 720P looked perfect durring setup but the actual image was so far off that I could not use it and inputting test patterns was of no use as the electronic parameters for convergence were crazy. I hope some day you remember what you did to fix this cause IMHO 720P, resolution wise, is the sweet spot for PG's.


Chip
 

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Discussion Starter · #16 ·
Chip,

The fix I had was located on the deflection board. I e-mailed the customer to see if I could come and take a look. Not sure they still have it but I do remember the fix ran for a couple of years with not other problem. Doug
 

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I'd be interested in buying a modded board from you if you figure it out.

Thanks,


Chip
 

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Doug,

really only 82 ohm for this "hook" resistor, you got 81 ohm together with the 12 Kohm parallel! It will put the pin 48 nearly to ground, or do you mean 82 kohm?

Then it is 10.5 kohm together, in the PG 9200 schematics its 10 kohms wanted!

Thank you,

Daniel
 

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One thing I'm not exactly clear on - I adjusted my voltage to 1.8v as described (had to decrease the width very slightly as it was around 1.86).

Quote:
There is a 10% plus or minus so if your short a inch or two it can be brought up to fill the screen depending on screen size.
Does the above statement mean that H amplitude should never exceed +10%? Or does it depend on how high a frequency you are using?

(I am running my PG6 at 1280x720 @ 48Hz and my throw distance is 1.51 screen widths if that matters - it does not seem to demonstrate the 's' curve either.)


Thanks-
 
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