CurtPalme.com Home Theater Forum

[ronaldus]

Hi everybody,

I'm trying to upgrade my 9500LC neckboards.

For the moment I've just changed the two capacitors C1 and C26 (original 22uf 100V replaced by 33uF 180V).

After I installed the VNB back in the projector I switched on the projector and I heard a loud tick (like an arc).

Strange thing is that it seemed to happen before the HV came in (not 100% sure). The projector fired up normally and the tube that I worked on (blue) worked normally. I switched the projector off with the remote and the unplugged it and took the VNB out to see if I could see something. All OK.

The only thing I didn't connect was the ground strip that normally goes from the VNB shielding to the big heatsink in the back of the projector.

Could that be the cause? Normally I allways have those strips connected.

For the time being I'm not very lucky with my mods

Could anybody shine a light on this?

Regards,

Ron.

[Nashou66]

Yes if those ground straps are not connected the static charge built up on the tube has no where to drain to.

Athanasios

[draganm]

[Nashou66]

[ronaldus]

Hy everybody,

This is what I've put in:

http://www2.mouser.com/Search/Refine.aspx?Keyword=66+7eca+2chg330&OrgTerm=66-7eca-2chg330&NewSearch=1

They are 160V instead of 180V. I guess i need new glasses

I guess I can continue with the carbon resistor changes. I've followed your recommendations Nashou and bought 2Watt ohmites. but they seem to be quite big. I hope they will fit in.

I also have a replacement for the HF1100 that's on my VNB's

For the VNB's I find i tricky to go with small steps because this means a lot of mounting and unmounting and i find the tube pins very fragile.

Anyway I'm glad i did with this first VNB. Maybe I can do the other VNB's in two steps; resitors plus caps then the chips?

Cheers,

Ron.

[ronaldus]

Hi it's me again,

I just discovered that the H convergence doesn't work anymore. I guess that spark hit something else then only the back heatsink )-:

If I move the H convergence it hardly moves but I see the green decreasing! All cables should be good because I didn't move them.

I now rember the the earth strip of the red VNB case was dangling in the projector when i switched it on.

Stupid beginners mistake!!

I hope i can repaire it.

Cheers,

Ron.

[draganm]

[ronaldus]

Hi,

Yes it's in the outer region. I've swapped with the blue tube and then it works so it's on the amplifier but it could off course come from the CLM since the green moves when I move the red (some crosstalk because of broken dac or opamp?) I'll check if i take teh two 24v jumpers out and see if the green still moves. If that's the case then I guess it comes from before the amp.

Cheers,

Ron.

[ronaldus]

Hi Everybody,

I've found the problem.

Q226 had blown up (I forms a constant current source for the push pull amplifier. I've replaced it by a general purpose PNP transistro (BC559) ant it works again.

I would have never thought that this sparks vould do such a damage.

I'm i happy man again:-)

I've attached a picture of the transistor.

[Nashou66]

[ronaldus]

Hi Athanasios,

The transistor is on the convergence amplifier and in this case it was on the RED horizontal channel.

To check that it was not on the CLM I tied the two control signals for H green and red together and when i did a convergence on red i saw the green moving so the control was working. Also the skew didn't work on red and that uses the same amplifier so that's another proof that the problem was on the amplifier.


The broken transistor behaved as an open circuit. So by measuring the voltage drop over base emitter i discovered that this one was broken.

I'll continue the upgrade of my other two neck boards.

I didn't see a lot of improvement but I only did the blue VNB.

I'll swap it with the green to see if it really makes a difference

Ron

[ronaldus]

Hi,

me again.

I've done a small test before after with only the two Electrolytic caps and 4 carbon resistors changed.

I was asthonished that there was a substantial difference after only the small changes.

I'll repeat this test when I have also changed the HF1100 chip.

Test was done in the center of the screen with a 1080P test pattern.
Photo taken with panasonic lumix on tripod with long exposure night mode.

I've added the same screenshot with also the chip changed.

I think with the old chip its better!

[Nashou66]

Yep, the VNB is like the Amp in an audio system, changing parts for modern better ones make a difference, sometime substantial.
Your Pics show this very well.

I found the chips help but not as much as some other things that can be done.

Nashou

[ronaldus]

Hi again,

I would like to compare the performance of my VNB with yours.

Could anybody try to show my test pattern on their projector and take a screen shot like i published in this thread?

Off course It'll test the whole signal path and not the VNB only but it would be nice to check it and it should not take much time.

for what i see now I can not resolve 1080p at all and I don't see scan lines at 1080p and 720p

My screen size is 2.4 meters wide.

I still have to do the Focus board mod.

It will be highly appreciated!

regards,

Ron.

[stridsvognen]

Hi Ron.

I just put up your test pattern, but directly out of my laptop 1080i to my VP50, and 1080P 72hz out from vp50 it only filled out 3/4 of the screen, this is how looks here with standard VNB

Should do better if i can put it up in native resolution. full screen.

[ronaldus]

Thanks Stridsvognen,

I'm looking forward to see the picture with the filled screen!

I'm running my projector at 60 hz

I've checked the image and it's 1924x1088 pixels

Cheers,

Ron.

[stridsvognen]

I just made the pics.. wait 15 min, my camera just need to charge a little before i can transfer the pics-

Kurt

[stridsvognen]

Here you go.... The best i can do.

[ronaldus]

Thank you very much!

I see that I'm not quite at your level.

I'll come back when I've done some upgrade to my focus board.

Cheers,

Ron.

[Nashou66]

Remember CPC magnet set up has a lot to do with Sharpness. Well, Set up in general.

Athanasios