CurtPalme.com Home Theater Forum

[jordanius]

Hey Guys,

I have a low hour second generation Sony 1272QM I am trying to calibrate for grayscale. I have tried endlessly to get the balance right but the picture remains washed out and underwhelming. A couple of questions I would love your input on;

- How can I get an accurate voltage reading from the CFB board as it seems entirely subjective based on what your bias/gain/contrast/brights are set to. Some post i've read suggest these should be at the halfway mark of 128 others suggest just going with whatever it reverts to when selecting factory. Is there a hard and fast rule for what these should be set at?

- Are you only meant to disable the AKB when setting G2 by eyesight? When I did this it caused the volt readings to shoot from 1.5v up to 3.5v. The light output also dropped and I could no longer see the IRE squares. Little twists of the G2 pots weren't reflected on my multimeter until I reenabled AKB at which point the readings were massively off. Why would disabling the AKB seemingly neutralise the effect of voltage readings. Do I need to turn them much further under this condition?

I am determined not to give up on this old beast of thing. Any assistance very much appreciated!

Thanks
Jordan.

[CasetheCorvetteman]

What is the brightness and contrast set to when you adjust this?

[jordanius]

Hey thanks for the reply, brightness and contrast always left at factory which is 50/80 respectively.

[CasetheCorvetteman]

Is there a special setup procedure listed in the Sony section on here?

analogrocks is abit of a Sony 12 series man, he will probably know where youre going wrong

[CasetheCorvetteman]

Have a read of this:

All Sony 12XX series sets with the exception of the 1270 and the 1292 have test points located on a small circuit board directly over the CA(G) and CA(B) circuit boards.

These test points are used to set the G2 voltage of each tube so that proper focus, color tracking and color balance is achieved.

The voltage is very easy to adjust, but requires the use of a DC voltmeter.

Set the contrast to 80 and the brightness to 50, the Sony factory default values.



As shown above, there are 4 pins on the black test point. The far left one shown above is for the red tube, then the others are for the green and blue tubes, and the far right pin is ground, which also is chassis ground.

Connect your DC voltmeter with the negative lead to the chassis and the positive lead to one of the test points.

You want to set the ‘screen’ or G2 controls (labelled DO NOT ADJUST) with an original Sony sticker over them so that each test point measures 4 volts, give or take 0.1 volts. Note that these adjustments are very touchy, a tiny turn of the screen control will make huge difference in the G2 test point. Here’s a decent result:



Once each test point is reasonably close to 4.0 volts, you should have a decent white balance and better focusing than if the G2 controls are set a mile off.

For white balance fine tuning, adjust your bias and gain controls on the keypad.

One of our readers has the following useful information to add:

"My understanding is that the gain and bias settings should be reset to factory settings and an unused input should be selected before making the G2 adjustment. This is my interpretation of the explanation in the service manual. My observation is that there is a significant difference in the voltage reading, especially if the composite input is selected, during the procedure.

I ran into another interesting phenomenon regarding the G2 voltages. I know this sounds unlikely however I have verified and resolved it. You know how twitchy the adjustment screws are? Well, I found that in my home theater environment that the LFE base is capable of rattling the adjustment screws enough to significantly change the adjustments. During the movie Master and Commander is when I first noticed there was a problem. The picture was normal at the start however became increasingly green as the movie progressed (Excellent Cannon Shots). Long story short, the voltages had changed to .3.5v, 3.8v and 5v from the heavy base. My solution was to fill the space between the adjusting screws and the outer housing with foam causing tension between the screw and the case. This prevents the screws from moving, however it does make the adjustment challenging because of the tendency for the elastic foam to spring back slightly during the adjustment. So you more or less have to over adjust then let it settle into the neutral position. I have not had a problem since the mod."

[CasetheCorvetteman]

Taken from here:

http://www.curtpalme.com/Sony125x_White_Balance.shtm

[jordanius]

Ah thanks for that Case, That's precisely the guide I've been following. The issue is my factory settings aren't the same as those mentioned by other people on the forums so was trying to understand at what point they should be set.

Paging Analogrocks.. any clues?

[rosenbush]

Trying to help:

- How can I get an accurate voltage reading from the CFB board as it seems entirely subjective based on what your bias/gain/contrast/brights are set to. -

Use them at the halfway mark of 128. It's just a starting point. Factory settings are useless at this point.


- Are you only meant to disable the AKB when setting G2 by eyesight?-

YES.

[jordanius]

Thanks very much for the advice Rosenbush.

After trying both I ended up disabling the AKB and setting the screen volumes by eye sight with the 5ire boxes barely visible on the background. The result is an improvement with the screen having more pop but the 'devastating' blacks CRTs are famed for continue to elude me. I think I'm nearly at the limit of what this projector can do. It's been fun but a an upgrade to a G70 is probably going to be my next port of call. How do other Sony 12xx's owners find their black levels compared to higher end units?

[CasetheCorvetteman]

Funny enough i had issues on both my 1001 QMs with a very slight washout of black in very dull scenes, it turned out to be the dynamic brightness setting causing it, i dont know if the 12s have it, but if they turn, turn it off.

[jordanius]

In a moment of indecision and inspired by another post I found I reenabled the AKB. With the bias's all at 128 and brightness backed off slightly the picture is much blacker and less washed out. The conclusion I've arrived at is setting the grayscale with the pluge pattern is never going to return a satisfactory result. I've ordered a colour meter and am going to have a go at the full calibration with Chromapure. Watch this space (and with me luck).

[jordanius]

Update :: after full grey scale calibration using a Spyder One and Colour HCFR Just wow!

I was never entirely happy with the picture before but now I understand what all the fuss was about. This old battle axe is now throwing the most film like image I've seen outside of a cinema. My faith in CRT is completely restored.

A note to anyone who acquires a Sony 12XX - Get yourself a colour meter and follow the greyscale for dummies guide, it is futile trying to do it by hand and the improvement will be dramatic.

Thanks to all who replied in this thread.
Cheers
J.

[CasetheCorvetteman]

No worries mate