CurtPalme.com Home Theater Forum

[Nashou66]

I tried and scoped all the other cables and looked at the images, only on the Astig it made a difference on my Longbows, on the Video cables it might also help a bit, didn't scope those yet. But on some connector pins for the cards it does benefit to add them there, the type that can ft over the pins if you lift them and re solder them back. Like some of the data lines but you have to test to make sure they do not alter them too much. I know the focus board Dac is a bit noisy, so on those it might help, i did notice a bit of a cleaner wave form but i didnt spend too much time as i was really after the Astig noise at the time.

Athanasios

[VideoGrabber]

> didn't you se my video on YouTube of exactly what your talking about? <

That's cool, Nash. A graphic depiction of the effectiveness of ferrite material to effectively damp unwanted high freq RF. Thanks for sharing.

Did you then observe an equivalent gain in stability (less noise) on your astig setup?

[WTS]

Not being totally familiar with the Marquee, which cables did you clamp the ferrite on? Watching your utube video, it sure got rid of alot of hi freq trash. Was that one main cbale or is there one for each - RGB?

[Nashou66]

Hi Walt, I had the scope connected to the Blue and Green channel if I remember correctly, Adding only one ferrite(TDK Z-Cat series) cleared up both channels.
That is noise that was either being produced the astig board itself or being picked up by the cables and then put into the board. i think it is the more the latter, being picked up and spread through the board, because just removing one astig connector from the circuit the distortions on the tube face went away. But TSE and MP think its board created. It probably is a bit of both.

And yes Tim, the astig set up really cleared up after as did over all focus, less flare on scanned lines even with the CPC mags not optimized.

I did try this on all other cables and only found it really helped the astig and somewhat on the convergence. No difference on the HDM's or VDM cables as far as I could tell. I did not want to scope the HDM cables since i don't have a probe to handle the 1000VDC. But just getting the probe close to the cables still had the flyback pulse wave clearly visible as with out.

Athanasios

[WTS]

So those are the cables going to the deflection coils?

[Nashou66]

[mp20748]

[Nashou66]

[mp20748]

It looks like they are doing some waveshaping on those boards, and the way they're doing it, it looks like a feedback circuit, which is probably why they are so unstable.

It's also one of the things I've been looking at lately. I've discovered a few things, but I think we may need to look into creating our own tech bulletin for this.

I spoke to Scott last week, he's now more involved with the newer digitals they're now selling. So with his, yours, mine and some others efforts we need to make this happen..

[Nashou66]

[VideoGrabber]

> So it is more Oscillation than anything else. <

If you crank up the timebase on your scope, you can see what the actual frequency is.

[Nashou66]

[VideoGrabber]

> I'm still figuring out my New 2445A scope <

Understandable. I've always liked the 2400 series Teks. One of my older scopes I've gotten good use from is a 2430A (not nearly as nice as yours).

What I had suggested was simply to change your horizontal timebase setting, until that variable intensity hash zone turns into a visible trace. You had it set around 5 uS/div, IIRC, which was 200 kHz. You'll probably need to adjust that to ~100 nS/div or so. When you get a stable trace, you can quickly tell the freq from looking at the period (f=1/p). That works with any scope. Of course, once you figure out the Parameter controls, you can just read it off-screen directly, the lazy way.

Similar identification of signal components can be done more quickly with an FFT, but your scope doesn't have than as an option (most didn't, though it has become more common... I have it on my cheap Rigol, as well as my LeCroys.).

[Nashou66]

[VideoGrabber]

Nash wrote:
> See to me all that is mumbo jumbo. <

Sorry. I'll try and do better.

> I was reading on mine that I can use some function to put up two vertical dotted lines that can be adjusted and the frequency between them will be displayed in a digital readout. <

Yes, you can use timebase markers, and then have the scope digitally display the period and frequency of the signal for you. But that's not necessary, and us old-timers have been doing it the "hard way" for many years. [Set the timebase (Sec/Div knob) so the width of one cycle is reasonable, slide the horizontal position over to align it with one vertical division on the graticule, and see how far over the next cycle starts. That gives you the cycle width (period) in divisions, which you then multiply by the horizontal time to get the actual period. So a cycle that was, say, 1.8 divisions wide, at 5 uS/div, would equal a period of 9 uS.]

I'll give you a couple quick examples that may be helpful. In your original scope shots on YouTube, there was a waveform hidden behind the noise, with spikes about one every horizontal division. (Horizontal is time, and the timebase setting is the big knob on your scope that's missing the central vernier adjustment.) The scope display indicated the setting was 5 uS/div, with one cycle per division, so the period is 5 uS, and that translates into a frequency of 200 kHz. (1/0.000005) = 200,000.

If you rotated the horizontal knob, you'd see the on-screen time readout drop from 5 uS to 2 uS and so on (in a 5-2-1 sequence). Eventually, that background hash in your original would start to take on a waveshape and sync (lock into position on the screen). You mentioned 10 MHz as a possible frequency, and if that was the case, you'd then be at 100 nS/div on the horizontal knob, if there was one cycle per division. Likely that's just the ballpark, but once there, you could find out the actual primary frequency of that noise.

Hopefully, that's a little bit clearer.