CurtPalme.com Home Theater Forum

**kal**

A G90 video bandwidth increase mod was mentioned in this thread here.

I didn't want to derail that thread so I'll ask here: What's up? This is the first time I ever hear of some sort of G90 bandwidth mod (or any G90 mods for that matter).

Anyone know the scoop? Who's doing this mod? What's involved?

Kal

JohnHWman · Posted: Thu May 17, 2007 9:17 pm Post subject:

There was a thread on AVS that talked about it. I should try to find it...

John

JohnHWman · Posted: Thu May 17, 2007 9:38 pm Post subject:

Here it is : http://www.avsforum.com/avs-vb/showthread.php?t=696950

John

rickwick · Joined: 21 May 2006 Posts: 20 Location: BC, Canada

OT somewhat Bomrat describes a Sony mod to a repaired df board in buy and sell section currently and glassact describes a critical chip replacement on that other forum for the G90.

**kal** · Posted: Fri May 18, 2007 1:02 pm Post subject:

Thanks for the link John!

G90 bandwidth mods would be interesting... even though there are less G90 owners out there than other lesser models, G90 owners are actually willing the spend the money. Smile

Kal

JohnHWman · Posted: Fri May 18, 2007 7:00 pm Post subject:

Yes Kal,

Money is not the first point about this, the challenge is more interesting 8)

One first way to go from my POV is to use a 500MHz oscilloscope, on BA board R or G or B paths. Feed 1080p signal with 1:1 B/W vertical lines test pattern on HD-DVD (HDMI outputed from toshiba XA2 and inputed to IFB-DVI card within G90 B slot) and probe all the video analog stage outputs Vpp to establish the weakest stage(s) in this signal path from IFB-DVI board until 'C' block on tubes necks.

Then we'll know were to put our efforts to inprove the stock 135MHz VBW to the highest value versus mod. cost (and technical limitations too).

Just one starting idea about this Wink

John

g90man · Joined: 16 May 2007 Posts: 30

Why John, it seems you're halfway done already! I'm really hoping this is something you are pursuing. Cross our fingers.

JohnHWman · Posted: Sun May 20, 2007 9:38 am Post subject:

I'll do, but probably later-on since I'm currently buzzy with my third G90 arrival (need to be retube) and IFB-DVI shipments Wink

John

Brian Hampton · Joined: 22 Apr 2006 Posts: 1173

Third G90.

Jeez. That's amazing.

-Brian

Joseph · Joined: 15 Dec 2007 Posts: 8

Thought I would bring this topic back from the dead; I'd love to see something done in the area of G90 modding, since
(like most everyone in this hobby), I'm always looking for ways to improve things. And as Kal wrote, the G90 doesn't lend itself to modding. I wonder if John has put any more thought into this?

overclkr · Joined: 08 Mar 2006 Posts: 4227

JohnHWman · Posted: Sat Dec 22, 2007 5:52 pm Post subject:

Yes, I understand guys ...

I would love doing these investigations but since I catched a new job in october, my spare time is quite low nowadays...

I still did not find time to change my own G90 unit Green C element (and redo 6500°K calibration) nor finishing my HT new wiring Sad

Maybe the day I'll catch my fourth G90, I will do it as it's always easier to do this kind of job on a spare machine rather than the one you use everyday Wink

As soon as someone is selling a G90 damn cheap, I'll buy it Very Happy

Merry christmas to all Razz

John

Joseph · Joined: 15 Dec 2007 Posts: 8

John, you've contributed so much to the community, I can't imagine anyone would complain about your schedule! FYI, I also revived the AVS Forum thread referenced in this thread, so perhaps there will be some activity there as well. Happy Holidays John!

Mark_A_W · Posted: Sun Dec 23, 2007 2:19 am Post subject:

JohnHWman · Posted: Sun Dec 23, 2007 10:09 am Post subject:

Hello Mark,

VBW is measured on video signals (0dB - 0.7V peak white on 75 ohms load) at the frequency where signal is lowered to -3dB.

Yes, this was me who did measurements of the G70 VBW between A and B inputs (three years ago). I did this only on the video side of the B board and not on the C blocks.

For the G90, this value is 135MHz and I assume that Sony made this measurment including the C block circuit (the VPJ15 video C blocks amp/drivers (G1/K) are rated at 150MHz). Cathode drive level should not matter as -3dB is relavive to the in-band cathode level (from within frequency response).

First (and easiest step) is to precisely measure the VBW of the BA board by inputing various RGB pixelclock frequencies (using Powerstrip for example) in either A or B(C) inputs of the projector and probe the C block delivered video RGB signals to catch the BW limit at -3dB. If this VBW is around 135MHz, then, we are sure that something can be done inside BA board circuits to increase this limit (by finding what is or are the blocs where this limit comes from 8) ).

If not, then the limitation comes from the C block circuits and we should work on the C block to extand this limitation (change of G1/K amp/drivers for example). But this part of the electronic is more complex to tweak since this would means special probing equipments due to the HV presence ...

Just my first thoughts

John

Ile · Posted: Sun Dec 23, 2007 2:01 pm Post subject:

JohnHWman · Posted: Sun Dec 23, 2007 3:43 pm Post subject:

Ile · Posted: Sun Dec 23, 2007 10:18 pm Post subject:

Yep, those have different specs.

VPA15/VPA18
max. Vcc 90V
Vout 40Vpp (80Vcc)
Gain 14

VPJ15 http://www.tenfourltd.com/pdf/SY103A_e.pdf
max. Vcc 120V
Vout 50Vpp (100Vcc)
Gain 15

JohnHWman · Posted: Mon Dec 24, 2007 9:17 am Post subject:

Thanks for the link Ile,

I'm quite suprized that the complete VPJ15 datasheet is so hard to find on the net ...
Anyway the VPJ15 Vout is far better than VPA18 and this should be a problem to use VPA18 for the G90. Don't know if VPJ18 did exist ...

My feeling woud be that 135MHz (-3dB) of the G90 comes from BA board and we should be able to extend it until 150MHz without too much difficulties Rolling Eyes

John

Joseph · Joined: 15 Dec 2007 Posts: 8

Good news to start 2008: it looks like Mike Parker is going to be examining a G90 very soon! Read his post here: http://www.avsforum.com/avs-vb/showthread.php?t=959357