CurtPalme.com Home Theater Forum

[Bucketfoot]

A week or two ago the picture on my 1270 all of a sudden got a fair amount brighter. Then this weekend it dropped back to normal.

Now I'm noticing the brightness pulsing from time to time.

Any suggestions on where I should start looking?

Based on the symptom I'm thinking it may be something power supply related. I wouldn't expect something connector related to keep doing this.

[tony359]

Try the magic solution: unplug all the cards and plugs, spray some dry contact cleaner on the pins of the plugs and reseat the cards few time.

Do it ai your own risk. And before do it, unplug the CRT for at leat 10 minutes before servicing it.

The brightness fluctuation is just one color or all three toghether?

Ciao
A

[Bucketfoot]

All three (verified by going into one of the setup screens and turning each on and watching individually).

I've got contact cleaner and will probably do the re-seating this weekend, but this does not smell like a connection issue to me.

[Curt Palme]

A power supply fluctuation will also usually be accompanied by height and width changes, indicating HV shift. I'm with Tony, check all of the module contacts to start. If not, I'd say it's a video issue.

But Tony, what is 'dry' contact cleaner? Any contact cleaner that I've seen is wet when sprayed.. Also, a good cleaner like Caig will leave some slight silicone residue behind, it's nonconductive, and will continue to clean and lubricate long after most of the cleaner has evaporated.

[Curt Palme]

A power supply fluctuation will also usually be accompanied by height and width changes, indicating HV shift. I'm with Tony, check all of the module contacts to start. If not, I'd say it's a video issue.

But Tony, what is 'dry' contact cleaner? Any contact cleaner that I've seen is wet when sprayed.. Also, a good cleaner like Caig will leave some slight silicone residue behind, it's nonconductive, and will continue to clean and lubricate long after most of the cleaner has evaporated.

[tony359]

Curt

I'm still waiting for my G90

When I reseat my cards for the first time the main advantage, beside the disappearence of the streaks, was to achieve a better brightness!

With "dry" contact cleaners I mean that ones that leaves no residue. There are some dehoxidizers that left a olily substance and has to be removed using some kind of cleaner.

I like to say "dry" because in Italy a guy followed my suggestions but with a dehoxidizer that he sprayed all around the cards (like a shower!). Plus, he didn't realize that reseating a plug on the DC card caused a +35V pin to slip backward.

The results are three heavily burned tubes and a Faulty DC board.

So, use a dry contact cleaner and do it at your own risk!

PS: Does the brightness fluctuations happen with internal generated test patterns?

Ciao
Antonio

[Bucketfoot]

It happens on both inputs and the internal test patterns.

[Bucketfoot]

Maybe I can use this as an excuse to upgrade...

We did after all just buy a brand new 46" 1080P LCD that is predominantly for my wife

[tony359]

Curt,

Could be a problem with High Voltage generator/regulator?

Ciao
A

[Bucketfoot]

So I re-seated all kinds of things a while back and that fixed the fluctuating brightness.

However as a result I ended up with a much brighter picture. To the point where I have my brightness setting at less than 5.
I can definitely watch it this way, but would like to get back to better black levels.

Any suggested next steps?

[tony359]

Start again with G2 and gain calibration. Set brightness to 50 and contrast to 80 before doing it.
Probably your BIAS values are too high.

You'll find the procedure searching the forum.

Ciao
Antonio

[Sonynut]

You need to readjust your Bias controls.. different people have different ways of doing it, but myself, I go to a no input condition, set my BRIGHTNESS control to 40, and blacken the room- I do mean pitch black-NO ambient light. now turn the status control to OFF, and adjust BIAS(one tube at a time with the other two cut off) down to the point where there is NO light hitting the screen, then turn it back up until one more click just starts to show light on screen. Do this for all three tubes, then press MEMORY briefly. Fire up a movie, and enjoy the blacks!. If the rest of your image is dull afterwards, you'll have to adjust the GAIN control. An easy way is to crank all three tubes up the SAME amount of clicks, until the one with the highest original adjustment maxxes out. After that, check a white screen to make sure its still white. If not, turn the GAIN down on the offending color that's tinting the white. Press MEMORY quick again, Then fire up a crosshatch pattern and adjust CONTRAST to 5-6 clicks below blooming. You should now have a nice punchy pic with great black levels. Gamma for shadow detail.. now thats a longer story, but there are plenty of threads out there on it.

My guess by this method is you will end up running BRIGHTNESS at about 42(without gamma correction) or 37(with gamma correction), and CONTRAST about 67.. Each machine is different though, and this HIGHLY depends on tube condition.

[Bucketfoot]

I've got a 1270 and thus do not have the test points mentioned, does anyone know where I would take my measurements?

[Sonynut]

You could use the G2 pots to adjust your blacks the same way as BIAS, but first perform a factory reset on BIAS and GAIN,, then set black with G2, and then fine tune it again with the BIAS controls. After that adjust GAIN as mentioned above.

[tony359]

1270 does not have G2 test point? I remember that 1270 has different voltage settings but I did not remember that it does not have test points.

I fully quote sonynut, but why Brightness at 40?

Ciao
A

[Bucketfoot]

[Bucketfoot]

The G2 levels had been set right before I bought the PJ, so I think I'll try Sonynut's bias adjustments first

[tony359]

No, if reseating the cards gave you the results you wrote, I would start again with G2 first, then Bias. Probably G2 has been set when you had some contact issue, and has been set too high.

Ciao
A

[Bucketfoot]

OK, then I guess I just need to figure out where to measure the voltages. I could do as Sonynut said and just adjust G2 the same way as he said for bias, but the voltage method has to be the better/more accurate way.

[tony359]

No, if AKB is activated, you must check G2 with a tester, and then adjust BIAS by eye as Sonynut told.

You cannot adjust G2 by eye if AKB is activated.

Ciao
A

[Sonynut]

Grab up the service manual for the 1270 off this site.. the G2 adjustment procedure has to be in there somewhere