CurtPalme.com Home Theater Forum

Axatax · Posted: Sun May 25, 2008 12:08 am Post subject:

ecrabb has the description of AKB on target. It's a closed feedback loop. If you look at the block diagrams in the service manual, you'll see there's a control line connected to a pin on each tube, which runs back to the C block, then back to either the B or Y* boards, which in turn signals the PA board to adjust output current for one of the CRT grids. That's *roughtly* how it works.

I personally leave this off, and periodically recalibrate.

garyfritz · Joined: 08 Apr 2006 Posts: 12088 Location: Fort Collins, CO

Basically the AKB is a known signal. The circuits look for the correct level of current on that known signal, and adjust until it's right.

Bitwize · Joined: 09 May 2008 Posts: 83

OK, I have received and installed the Moome HDMI card. My buddy Chad B. recalibrated the grayscale and we did some rough gamma adjustments using the Moome's gamma circuit. Convergence was also tweaked up a good bit. The resulting picture looks incredible and Chad said he has never seen a G70 with such good focus. 1080p looks fantastic and I'll be taking some screenshots soon. Also, my wife so graciously put together some nice velvet curtains and a valance to go around the left/right/top edges of the screen. This helped to soak up more light resulting in black that looks absolute Smile

My humble little home theater is nearly complete now. Just need a few more movie posters on the walls Wink

Zebu Fellenz · Joined: 21 Dec 2006 Posts: 2567

I can't wait for some screenshots.

I run my G70 (Non VR) at 1080p and would like to see how it compares to the VR.

Erik

Phil Smith · Joined: 08 Mar 2006 Posts: 7717

I don't know why my ABK experience was so different from you guys. My ABK line was very dim, I rarely saw it and if I turn it off everything went to sh*t. I couldn't crank the brightness enough to get a decent picture. Shocked

ecrabb · Posted: Tue Jun 17, 2008 4:42 pm Post subject:

Yeah. Screenshots. Screenshots.

Phil, you can't just adjust brightness... You leave the brightness control in the middle and adjust G2... THEN brightness will be back in range. Of course, black point is all F'ed up if you go back and turn ABG on, including super-bright raster with retrace lines and the whole nine yards.

Annoying thing is, I still have the AKB line even with ABG off. Knowing that, combined with the fact that Cliff says the line shouldn't even be in the active image area, and that if it is, the projector isn't set up properly... and is probably the reason for my flickering... means I need to do a setup again and see if I can get it right.

I wish one of the old G70/G90 setup 'sperts was around and could just give us a couple of hints on setup. Does anybody know if Terry (Chuchuf) or Bruce (techman707) are ever in this forum? Come to think of it, what happened to Bruce? I haven't seen a post from him in a long time over at AVS.

SC

Axatax · Posted: Tue Jun 17, 2008 4:45 pm Post subject:

ecrabb · Posted: Tue Jun 17, 2008 4:52 pm Post subject:

Sorry, Rob - thread detour - I think it's still relevant, though...

So, Axatax... Question for ya... When you do setup with internal patterns... Where do you have the edges of the patterns fall? The first time I did it, I did it just like the old 1271 - with the ends of the cross-hatch on the edges of my 16:9 screen. The results of that were bad all around: Poor convergence and geometry in the corners, lots of zone to get them into the ballpark, and of course the AKB line well into the top of my image area. The second time I set it up, I set up with edges of the test pattern well off the screen - probably 6 inches or more. That definitely helped. Geometry and convergence in the corners was better, it was more stable, and overall image was better. The AKB line remains, though. Any idea what am I doing wrong?

Thanks,
SC

Axatax · Posted: Tue Jun 17, 2008 5:07 pm Post subject:

Could you take a picture that shows the AKB line?

Brian Hampton · Joined: 22 Apr 2006 Posts: 1173

Hey,

Just wanted to say... I'll play along.

When I have AKB off I get no AKB line unless I mute the picture.

However,.. AKB on has a serious affect on the picture which is why I've gone back and forth between using it and dis-abling it. Usually I have it dis-abled.

I've re-enabled it yet again and for the moment things seem great. .... I'll see if I can live with it on for a while.

Maybe the order in which you turn things on can throw AKB for a loop with the various HDMI input options. Seems like after a few sessions with AKB on I was un-able to get blacks that were black with the brighness set to 0 and that's why I turned it off.

-Brian

ecrabb · Posted: Tue Jun 17, 2008 6:10 pm Post subject:

Axatax, thanks - I'll take a few pics so you can see what I'm looking at.

Brian, as I said previously - G2 will absolutely need to be adjusted when going back and forth between having ABG on and off.

If the blacks are good when you have ABG on and you then turn it off, you'll have a super-dark picture and you won't be able to get enough brightness even if you crank brightness wide open (Phil's situation). You have to increase G2 level to compensate.

If, on the other hand, things are set up right with ABG off and you turn it on, then you'll have a bright raster with visible retrace, and turning brightness all the way down won't even be able to compensate (your situation). You have to decrease G2 level to compensate.

Who were is running 1080p and what's your source? My flicker problem only showed up at 1080p, and then only with certain source material. The rest of the time, I only noticed some "bounce" in brightness... For instance, clicking through the menus in the PS3 XMB would produce a tiny bounce. Obviously, all that is gone with ABG off, but the AKB line still remains. I'll snap a few photos.

Can't wait to see some picks of the VR setup, Rob.

Thanks for the help, everybody - can't wait to "get there" with my G70 - the G70 is one hell of a machine.

Side note. The wife and I went to a home show last weekend. Several of the houses had dedicated HT's, and were all in the $600k-$1 mil ballpark. There were a couple of Sony Pearls and a couple of Runcos - both obviously 1080p, judging by the size of the pixels on-screen. Obviously, the conditions weren't ideal and I doubt they were calibrated (neither is mine)... But, those setups look like ASS compared to my G70 setup. I mean, there was no comparison. My theater just SMOKED every one of them. I left feeling all warm and fuzzy.

SC

Brian Hampton · Joined: 22 Apr 2006 Posts: 1173

Well,

AKB started giving me trouble the second time I turned stuff on. If I used any blanking along the top the picture got too bright. Setting the top blanking back to max solved it but it's still weird.

Anyway,... G2 is not adjustable with my FW so we need not discuss that one in detail.

-Brian

ecrabb · Posted: Tue Jun 17, 2008 7:35 pm Post subject:

Phil Smith · Joined: 08 Mar 2006 Posts: 7717

Bitwize · Joined: 09 May 2008 Posts: 83

FYI, had to have the G70VR recalibrated over the weekend. My green and blue tubes were relatively new so after a couple hundred hours of break-in, the grayscale and focus had drifted a bit. Things are much better now. In addition, I now have 720p and 1080p tweaked out. I took some screenshots but not sure they are going to be that great due to my lack of camera skillz and equipment. Will post them pretty soon hopefully.

Btw, the brightness uniformity had to be disabled (set to OFF) as it was causing glowing corners even with a completely black screen. The glowing could be minimized with very low brightness but this was not ideal. Not sure what is going on there, but the screen is much more uniform with uniformity turned OFF now.

Bitwize · Joined: 09 May 2008 Posts: 83

how many foot lamberts are you all getting with your G70s??? just curious if i'm in the ballpark. thanks!

fyi, the screenshots are crap as expected. i'll have to have my buddy come over with his good camera and photo skillz to take some new shots.

Bitwize · Joined: 09 May 2008 Posts: 83

I posted this in the "CRT Foot Lamberts" thread but thought it would be good to have here as well...

"i decided to go back to 11.5 ft/l as anything 12+ was stressing the G70VR a bit much. seems 11.5 is the sweet spot for this PJ. with the brightness and gamma adjusted correctly, 11.5 still looks quite nice. i did discover something odd last night though...

sometimes the PJ syncs to the PS3 and Xbox 360 at a horizontal freq. of 60, but it also syncs at 59.7. This slight difference requires me to have 2 memory banks with the exact same settings as I never know which one it will choose. ALL the settings are exactly the same for both memory banks, but for some reason 59.7 looks better! The image is just more "3d" and contrasty. I honestly don't get it. Should that 0.3 difference in freq. really affect image quality? Like I said, all the numbers are identical aside from the H freq."

Bitwize · Joined: 09 May 2008 Posts: 83

Please see my post regarding a scaler...

https://www.curtpalme.com/forum_archived/viewtopic.php@t=11483.html

Bitwize · Joined: 09 May 2008 Posts: 83

OK, based on my buddy's recommendation...I'm considering the Lumagen VisionHDP. Here's my proposed setup. Please comment or advise as needed...

Xbox 360 (1080p/60), PS3 (1080p/60), Dish 622 Receiver (1080i/60) -> Onkyo Receiver (HDMI Inputs) -> Lumagen VisionHDP (HDMI to DVI) -> Output 1080p/60 to Moome HDMI card in G70VR (DVI to HDMI).

I'm mostly interested in having the Lumagen VisionHDP for grayscale and gamma calibration/correction, but also for scaling the Dish 622 to 1080p/60. Does this sound like it will work? I seem to remember reading the Lumagen VisionHDP takes 1080p/24 input...will it take the 1080p/60 OK?

Thanks in advance!