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Post by tschaeikaei on Dec 30, 2015 1:28:14 GMT -5
I've done the resistor & cap mod on one of my HVPS today. The 560k were at 620k.
Didn't measure more than that, also changed the 1µF and 0.47µF caps.
And two 10 Ohm resistors on the daughter board.
The big caps on your pics Nash, are they simply in parallel to the 0.47µF caps?
Why tantalum?
I guess it would be wiser to work at the LVPS 390V output and maybe lower impedance there than adding huge caps
that will only helo for a few miliseconds if more current is drawn.
Since there are so many different HVPS versions,
i even ordered some resistors (e.g. R1) not beeing present on mine (Rev. B4).
But nice results. Very visible noise lowering.
Next project will be the LVPS, all I've done there is a fan mod, there will be more work, i'm sure.
Feel free to link some info about HVPS and LVPS mods.
Regards, Julian
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nashou
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Post by nashou on Dec 30, 2015 9:27:26 GMT -5
I've done the resistor & cap mod on one of my HVPS today. The 560k were at 620k. Didn't measure more than that, also changed the 1µF and 0.47µF caps. And two 10 Ohm resistors on the daughter board. The big caps on your pics Nash, are they simply in parallel to the 0.47µF caps?
Why tantalum?I guess it would be wiser to work at the LVPS 390V output and maybe lower impedance there than adding huge caps that will only helo for a few miliseconds if more current is drawn. Since there are so many different HVPS versions, i even ordered some resistors (e.g. R1) not beeing present on mine (Rev. B4). But nice results. Very visible noise lowering. Next project will be the LVPS, all I've done there is a fan mod, there will be more work, i'm sure. Feel free to link some info about HVPS and LVPS mods. Regards, Julian Hi Julian. Chris Stevens who did those original Wet tant mods on the famous Accurate Imaging Reference 9 Projector said at the time they were the best caps to use. But since then they came out with Film caps whos ESR are lower than the wet tants and now are much smaller than 20 years ago when Chris was doing the mods. I have some emails from him explaining much of why he likes Wet tants, he basically replaced every electrolytic cap in the PJ with Wet tants. One reason he went after the 390 line in the HVPS is that the transmission line pics up a lot of noise along the way from the scope redding he did at both ends. So he cleans it up at the HVPS, basically like every other board. PS: yes the caps are in parallel , Much cheaper solution than wet tants  And better results. Chris said that adding more uf's helps in the dynamic range transients from black to white as well as get more noise out of the image. Nashou |
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Post by tschaeikaei on Dec 31, 2015 12:09:16 GMT -5
I have a bunch of 390µF 400V electrolytics lying around. It would be better with 450V types, but yeah.
Is there higher voltage than the nominal 390V to be expected?
They are Hitachi HP3 type and used. According to the datasheet, 0,275Ohm at 20°C (room temp) and 100Hz.
I expect the ESR to be rather good (in comparision to other caps datasheets).
What capacity do you use?
Regards, Julian
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nashou
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Post by nashou on Dec 31, 2015 15:30:16 GMT -5
I have a bunch of 390µF 400V electrolytics lying around. It would be better with 450V types, but yeah. Is there higher voltage than the nominal 390V to be expected? They are Hitachi HP3 type and used. According to the datasheet, 0,275Ohm at 20°C (room temp) and 100Hz. I expect the ESR to be rather good (in comparision to other caps datasheets). What capacity do you use? Regards, Julian 390uf is way to high. About 20-30uf is what Chris recommends . Any higher and it could cause start up issues. Nashou |
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Post by tschaeikaei on Dec 31, 2015 17:45:25 GMT -5
Do you mean 20-30µF each or 20-30µF both together. They are in parallel, aren't they?
Regards, Julian
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Post by gjaky on Jan 29, 2016 11:38:51 GMT -5
Nice  The noise issue probably is grounding related. Or get a noisy machine, disconnect all yokes (convergence/stigmator/focus) except the deflection yoke of course, if the noise is still there, then the problem coming from the VDM. |
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Post by gjaky on Jan 29, 2016 15:23:22 GMT -5
Well it has to be something... |
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Post by gjaky on Jan 30, 2016 10:06:37 GMT -5
I think my NEC do similar thing with the scanlines, also my friend with a BG808 reported similar behavior. So this should be a general "issue", I'd also welcome a solution.
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nashou
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Post by nashou on Jan 30, 2016 16:18:40 GMT -5
If you scope the GND on most PJ's there is always noise there. Scott told me this mostly comes from the Fly back circuits in the HDM more than any where else.
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Post by gjaky on Jan 31, 2016 2:37:48 GMT -5
One thing that came into my mind is maybe the difference in the coils, H and V def coils are on the same core, so the windings can have cross talk, and as already being said the H deflection makes quite some noise which could be picked up by the V def coil affecting the resulted image.
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Post by gjaky on Jan 31, 2016 6:00:48 GMT -5
VNB? All these have the new style VNB?
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Post by gjaky on Jan 31, 2016 12:24:18 GMT -5
Just for the fun you should swap to an old style VNB (and VIM if needed) BTW, did you go for the 9500LC in Hamburg on eBay? |
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Post by radiohead314 on Mar 3, 2016 23:25:28 GMT -5
I tested my 9518lc with standard new style neckboards and vim with trimpot and lugs. I looked if it was true that the gamma had a problem but it went reasonable straight, no problem when I maxed the lightoutput around 10 ftL on worn lugs. The bandwidth was exeptionally good it was good compensaed with the trimpot on the vim in my case at 1080p. From low till high ire levels perfect 1:1. This surprised me after all the stories that these newest marquees where the worst ever. My findings are that they do not need any mod in the video. Probable the noise mods have to be done on other boards and other performance mods might still be usefull.
To better judge thse I need to watch some movie material and I need a bigger testscreen in my test setup.
I will post some of my testpictures to better point out my findings.
So surprised about these machines!
Have to see how the blacklevels are. Might need a mod with the switching stuff on the vim and the lines?
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Post by radiohead314 on Mar 3, 2016 23:34:30 GMT -5
Look at this, 9ftL just green so that is something like 11ftL white with contrast 70. No strange thingss incredible bandwidth. What is there to improve? But this was with g2 a bit high. They are a bit dimmer like 10 ftL The multiburst shows that 4 3 2 1 pixels come at the same intensity. No bumbs or non linearity. Also the whole greyscale from 10 ire till 100 ire 1080p is 100% resolved. Never seen that before.  Untitled by Radio Head, on Flickr  Untitled by Radio Head, on Flickr  Untitled by Radio Head, on Flickr  Untitled by Radio Head, on Flickr  Untitled by Radio Head, on Flickr  Untitled by Radio Head, on Flickr |
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Post by radiohead314 on Mar 3, 2016 23:38:55 GMT -5
When calibrating nice and using contrast 72 where everything seems ok I get between 10 ftL and 10,5 ftL white intensity. With worn tubes that is not bad at all. I also looked at the gamma at contrast 72 as there are stories that these have very strange gamma that break up or something. Well this one has a very normal gamma of 2.4. I have seen them a bit flatter but you will not notice this. It has been said that the gamma is not completely flat because the tubes are badly worn.  Untitled by Radio Head, on Flickr  Untitled by Radio Head, on Flickr |
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And better results. Chris said that adding more uf's helps in the dynamic range transients from black to white as well as get more noise out of the image. 
