CurtPalme.com Home Theater Forum

[draganm]

[Nashou66]

I am very curious about the magnefilm as its rated into the kilohertz, very low, this might be what we are looking for. I should build on of those Gauss meters that jarmo linked to, looks like a fun project just to see what the EM fields are like, also it really help with my barkenstien project I plan to get back to someday, hopefully

Athanasios

[mp20748]

Here's a filament mod I did the other day. It's using only one inductor, but does an excellent job cleaning up the noise.

I'm sure I've played around with this before, and can remember doing a comparison with the scope and by watching the image. Also had an inductor on my test unit right at P14. Though I've been able to see a difference when looking at things on the scope. But have never been able to see a difference in the image. So that's why it was never implemented to my main Marquee.

Below are before and after shots. The before shots were taking a few weeks ago and from this same batch, I posted over on AVS. In each of the before shots, the two top patterns in the six pattern group are not matched (hue/tint). There's a green ting in the top left with a bit of blue in the top right, while the other four shows equal. Color balancing would not correct the difference.

In the after shot (taking today), both top patterns in that six pattern group are more equal. The horizontal lines are also more defined. What was more noticeable was the overall change in gray scale.

I'm still somewhat puzzled here, but from looking at the smpte pattern on the screen after the mod, it seems to have removed a color tinge that I was not able to get rid of on these boards.

I'm not claiming anything here yet, but there is a difference that I don't understand why and what's going on yet.




before (notice the color difference in the two top patterns - not corrected w/calibration)



recent (notice that the color difference is no longer there, the horizontal lines and overall gray scale difference)

[Nashou66]

I see the difference, I wonder how this filament mod would alter greyscale? looks like you kept the original ferrite beads there and added the inductor and some caps to gnd , a simple LC filter. I agree why would this alter the grey scale that much ? You can see it did clear up the definition on the lines and got rid of the tint, but it gave the solid grey boxes a different shade of grey almost on the yellow side? I wonder what HCFR or Calman would show on the chart? if the whole scale shifted to the green/blue end of the chart? What was the voltage after the LC filter there?

Athanasios

[HK-Steve]

Nice pics Mike,
What size was the inductor that you used??
I would be interested in testing a few values and see which is the sweet spot.


Strange about the correction on the color balance, or green tinge.

I see that you also added the 1uF caps at the diodes,
I put mine across the diodes,

Why did you go to ground?? , as I didn't see much improvement when I went to ground.



Cheers
Steve

[draganm]

that's a HUGE difference to my eye's! I can't believe no ones ever found this before. I mean people have spent hundreds of dollars to get a much smaller improvement than that. We have an increase in ANSI CR and color balance, that's a big deal IMO.

[mp20748]

[1031]

[draganm]

[Nashou66]

Drags I assume you will have to go into the G2's and adjust there for the proper black level afterwards, Lets wait and see what Mike finds first .

I cant wait till I get the 2nd PJ up on the ceiling so i can get back to what I really like to do , experimenting with different things on the Marquee.
My sore back has healed a bit so this past week little by little, 20 minutes at a time, i got the unistrut up to attach the top part of the pulley mount to. Now I have to take down my Trusty old M8000 and haul up the 2nd Long bow. But having screwed up the first Pj's mounting so many times this one will go up much smoother.

I am still curious if the voltage for the filament changed much from the P14 pin to the point after mikes mods on the VNB? I wonder if lowering the heater voltage would change that brightness issue. if I am not mistaken doesn't that voltage contribute some to how Bright the overall tube will Project. i remember reading somewhere that somebody had the voltage too low and when they raised it to the Proper 6.35 volts the image brightened up? So maybe that cleaner heater supply is like having more voltage to the heater? Hmm Would that then speed up decay of the heater element as if the p14 voltage ran away on you?



Athanasios

[draganm]

[mp20748]

A picture of the inductor I'm using (including one without the shrink).

Absolutely NO DC voltage drop..........




If I get a chance later, I'll hook up the digital scope and do a dual trace showing a stock board in comparison.

[Nashou66]

Ok, no voltage drop. one variable out of the way. So it could be as I mentioned then; the cleaner supply voltage acts as a higher voltage. But since the spec's for most tubes heater elements is 6.35 volts , and I am sure they do tests with supper regulated voltage supplies, then we may be just seeing the CRT behaving as the original designers intended? What do you think Guys?

So Mike when you say an elevated low end do you mean it is just brighter or that the shadow details are more pronounced now?


Athanasios

[mp20748]

[Nashou66]

[tse]

[tse]

[Nashou66]

[mp20748]

[mp20748]

Here's two shots showing the lines. I have a piece of plain white paper taped to the screen right on the vertical one pixel lines.

Both shots are not well focused, but they should give a good idea of what's going on with the screen.