CurtPalme.com Home Theater Forum

redfox001 · Joined: 16 Mar 2009 Posts: 2257 Location: The Netherlands

Mind the bandwidth pictures where made with the potting material just as I received them.

**Curt Palme** · Posted: Sun Feb 14, 2016 4:12 pm Post subject:

Guys, can we keep it civil, please? Insulting one another isn't going to solve anything. If you want to question the performance of mods by anyone, do so nicely and post pix of proof. Simply going on the attack and posting name calling is pointless.. and has gotten members banned from this and other forums.

tschaeikaei · Joined: 08 Apr 2013 Posts: 490 Location: Germany/Saarland

If the goal of this COMMUNITY is to get the best possible result in PQ and resulution out of a CRT projector,
my vote is that everyone should work together. It is far too complex for a single person alone and
far too much work. Share your results and observations, not complaints.
So if we want to succeed, there is no point in posting offendings against a single person.
If i had a problem with anyone i would write a pm or email. Where is the point in this?
If the solderjoints are bad, resolder them. Ask the person to get some % of your money back if it's his fault.
Send the parts back if you don't like them. But don't flame in an open forum everyone in the world can read.
Regards, Julian

**Curt Palme** · Posted: Sun Feb 14, 2016 4:57 pm Post subject:

Exactly. It seems the less CRTers there are left in the world, the more nasty the community has become. Not cool frankly.

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

I agree, this personal fighting is getting out of hand. You two, please keep your dispute private. You know who you are.

Anyway, any time you're talking about reproducing true square waves, you're automatically talking about theoretical infinite bandwidth, and since the electron beam has a Gaussian polar power distribution profile, there isn't any way to achieve a perfect sharp edged, 100 percent MTF value, pattern on a CRT. Thus knowing that you can't achieve an MTF of 100 percent, this greatly relieves us of any NEED to try to get the kind of bandwidth required to obtain the theoretical but optimal 100 percent MTF.

Instead, identify an MTF value that is functionally useful to a discriminating viewer. (Assuming that only a discriminating viewer would even still be playing with a CRT projector instead of a digital viewing solution.)

At what MTF value does the one on, one off pattern achieve the level of resolved contrast that all viewers are likely to be satisfied?

When you identify that specific goal and are able to measure the MTF values of boards under test and correlate them to bandwidth requirements, then you will be able to establish the bandwidth goal that achieves it.

But this is predicated on the idea that your electron beam spot size and profile is adequately small and sharp shouldered enough to even theoretically achieve your goal.

Enginering a 1 GHz, totally linear and gamma corrected signal path is wasted effort if you don't have the spot size and profile to resolve more than a 250 MHz worst case test pattern.

You DO have the capacity to measure MTF values, do you not? It's not difficult. It essentially takes a video camera with a video output on a BNC or phono type connector, , a grid test pattern, and an oscilloscope. And you do it with a standard definition camera, not an HD camera, and the video output is plain composite video.

Ask Tse for details about his MTF measurement setup. He can tell you exactly what's needed.

redfox001 · Joined: 16 Mar 2009 Posts: 2257 Location: The Netherlands

I objected to Mikes clame that he can modify neckboards to very much higher bandwidth than they are standard and I provided pictures for that and arguments (there are only two high bandwidth parts modified). I am leaving it with this.

**Curt Palme** · Posted: Sun Feb 14, 2016 5:59 pm Post subject:

I don't have a problem with challenging someone's claims with facts and images. I have an issue with people calling out someone else's morals and then the mudslinging starts....

Keep it technical and civil. That applies to everyone on this forum.

mp20748 · Posted: Sun Feb 14, 2016 8:14 pm Post subject:

mp20748 · Posted: Sun Feb 14, 2016 8:23 pm Post subject:

gjaky · Joined: 05 Jun 2010 Posts: 2802 Location: Budapest, Hungary

It is about 130MHz pixel clock, so about 65MHz pure sine bandwidth, of course your system should have a higher bandwidth than this to resolve this without loss.

mp20748 · Posted: Sun Feb 14, 2016 9:04 pm Post subject:

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

I am going to suggest to all of you really large-brained technical types who are involved in actual circuit modifications to settle on a measurement standard.

I suggest the most functional measurement standard: Not pixel clock, but resolution, refresh rate, and scan rate, for a defined test pattern, and give measured objective MTF values.

If you use the same measurement conditions and methodology, there will be no basis for an argument which has started primarily over a differing interpretation of signal conditions.

Incidentally, the pattern generator that Mike uses can be had for only a few hundred dollars. I just checked. There's one on ebay and it's cheap enough that I'd snap it up right now if I had much interest in doing my own research and experimentation.

Use the same generators and the same patterns and the same measurement methods and you won't have anything to argue about.

mp20748 · Posted: Sun Feb 14, 2016 9:19 pm Post subject:

redfox001 · Joined: 16 Mar 2009 Posts: 2257 Location: The Netherlands

redfox001 · Joined: 16 Mar 2009 Posts: 2257 Location: The Netherlands

mp20748 · Posted: Sun Feb 14, 2016 9:37 pm Post subject:

[quote="redfox001]I think you could get a 250MHz pixel clock from the neckboards. Perhaps if you are lucky you find one tuned perfect to do 300MHz perhaps a little overcompensating. But that would be standard your mods do not change that much.[/quote]

Did you understand what Curt was saying?

redfox001 · Joined: 16 Mar 2009 Posts: 2257 Location: The Netherlands

redfox001 · Joined: 16 Mar 2009 Posts: 2257 Location: The Netherlands

mp20748 · Posted: Sun Feb 14, 2016 9:48 pm Post subject:

gjaky · Joined: 05 Jun 2010 Posts: 2802 Location: Budapest, Hungary