CurtPalme.com Home Theater Forum

[jbltecnicspro]

So the PA board came back from Curt and the projector lives again. Yay...

Except that the green tube is now stupid dim. Dim enough that white is now pink. Very little wear on the tube, and it was perfectly bright before. As far as I can tell it's not broken (surely it's not - it would lose the vacuum and not work at ALL).

Here's what I've swapped:

1. Swapped neckboards
a. Swapped in a new-style (I have an old-style) neckboard and the picture got even worse. Stupid dark.
b. I have not swapped in another old-style neckboard but I don't see the point as even beforehand the new-style neckboard never behaved like this.

2. Swapped RGB boards
3. Swapped video cables (exchanged green and blue at the RGB board to see if the problem would go to blue - it did not)
4. Swapped cables from the motherboard leading up to the neckboard.


None of the things I've done above have helped the situation. I'm not running any signals into the projector and at this point all I'm doing is hitting the "Menu" button. What else can I do?

Side thought - could I just swap my working PA board into the parts projector that has an Error 21 (likely a PA board failure)? What will happen if it's not compatible? Just no bootup?

EDIT: I'm also troubleshooting with Curt via email (thanks Curt ). But I was wondering if anyone else had any ideas as well.

[jbltecnicspro]

So I'm doing more and more searching on this issue and I cannot find a solution. To my eyes, it looks like the G2 is simply too low on Green. I turn the brightness down to minimum and as soon as I lower contrast all the way, the image becomes (more or less) invisible on green, but still barely visible on blue and red.

I'm not using any video input at all. I'm simply adjusting the brightness and contrast to minimum and hitting "menu" to bring up the menu and see how bright it is on the tube face. Red and Blue are visible, green is pretty much invisible.

Green has very little wear on its tube face and prior to the PA board going south, it had very high output. Does anyone have any ideas as to what could be going on? It's definitely not a video problem. Do I need to reset the G70 so that it can reestablish the proper G2 levels for each of the tubes?

[Curt Palme]

No, don't do any reset.

As I said via email, the PA board tested fine here, and I had equal brightness on all 3 tube faces. I just can't see it being a PA board issue.

Have you adjusted the gain and G2 settings while in the service menu, via the keypad? It's normal for the G2 and gain settings for the green tube to be almost maxed out.

If by swapping the G2 leads between red and green you say the red became blindingly bright, then the output of the green G2 pin is fine, and is leaning towards being a weak tube. Despite the tubes having little wear, if the set was on for close to or over 10,000 hours, then the electron gun may be weak itself. At this point I'd swap in the more worn green tube that were originally in the set to see if the brightness comes back on the green tube.

[Curt Palme]

No, don't do any reset.

As I said via email, the PA board tested fine here, and I had equal brightness on all 3 tube faces. I just can't see it being a PA board issue.

Have you adjusted the gain and G2 settings while in the service menu, via the keypad? It's normal for the G2 and gain settings for the green tube to be almost maxed out.

If by swapping the G2 leads between red and green you say the red became blindingly bright, then the output of the green G2 pin is fine, and is leaning towards being a weak tube. Despite the tubes having little wear, if the set was on for close to or over 10,000 hours, then the electron gun may be weak itself. At this point I'd swap in the more worn green tube that were originally in the set to see if the brightness comes back on the green tube.

[jbltecnicspro]

[Curt Palme]

Sony's ABG circuit causes havoc when swapping g2 leads, etc, but it's encouraging that the other red tube does it in the same slot as well. If you have a voltmeter that can read 500-800 volts, you can measure those G2 pins. DO NOT disconnect and 'float' those G2 pins and turn the set on, measure while the pins are connected in circuit. you should read 500-800 volts depending on the level of the G2/gain controls in the menu, and they should all be similar in min/max voltage value as you go from 0 to 254 in the settings of each.

[Curt Palme]

Sony's ABG circuit causes havoc when swapping g2 leads, etc, but it's encouraging that the other red tube does it in the same slot as well. If you have a voltmeter that can read 500-800 volts, you can measure those G2 pins. DO NOT disconnect and 'float' those G2 pins and turn the set on, measure while the pins are connected in circuit. you should read 500-800 volts depending on the level of the G2/gain controls in the menu, and they should all be similar in min/max voltage value as you go from 0 to 254 in the settings of each.

[jbltecnicspro]

[jbltecnicspro]

Okay - I don't have a voltmeter that can go that high (yet). Anything else I can test while I'm trying to procure one?

[Curt Palme]

That's really the next step. Any good digital Fluke or similar brand meter should go to 1000 volts though.

[Curt Palme]

That's really the next step. Any good digital Fluke or similar brand meter should go to 1000 volts though.

[jbltecnicspro]

Something like this should do? https://www.amazon.com/Klein-Tools-MM700-Auto-Ranging-Multimeter/dp/B018CLOSTC/ref=sr_1_7?ie=UTF8&qid=1473701217&sr=8-7&keywords=1000v%2Bmultimeter

[Curt Palme]

Never used one of those, get a used Fluke:

http://www.ebay.com/itm/FLUKE-73-III-MULTIMETER-WITH-RED-BLACK-LEADS-WORKS-GREAT-GOOD-CONDITION-/262612737076?hash=item3d24f05c34:g:WZIAAOSwxg5XxMCd

[Curt Palme]

Never used one of those, get a used Fluke:

http://www.ebay.com/itm/FLUKE-73-III-MULTIMETER-WITH-RED-BLACK-LEADS-WORKS-GREAT-GOOD-CONDITION-/262612737076?hash=item3d24f05c34:g:WZIAAOSwxg5XxMCd

[jbltecnicspro]

Borrowing my friend's Snap-On multimeter - good to 1000 volts. So where the heck am I putting these tips? Yes - I'm a noob.

[Curt Palme]

Negative goes to the metal chassis, the positive goes to each one of the G2 leads. Measure the R G and B voltages. If everuything is OK on the PA board, all should probably be within 100 volts of each other. Also, as you adjust the 'bias' on the keypad or remote, the voltages should ramp up and down along with ramping the keypad. Min and max voltages should all be similar between the three points.

If the test probes are too thick to fit down between the wire and the connector going into each one, then use something like a cut off paper clip to stuff between the wire and connector, and touch the probe to the end of the clip.

[Curt Palme]

Negative goes to the metal chassis, the positive goes to each one of the G2 leads. Measure the R G and B voltages. If everuything is OK on the PA board, all should probably be within 100 volts of each other. Also, as you adjust the 'bias' on the keypad or remote, the voltages should ramp up and down along with ramping the keypad. Min and max voltages should all be similar between the three points.

If the test probes are too thick to fit down between the wire and the connector going into each one, then use something like a cut off paper clip to stuff between the wire and connector, and touch the probe to the end of the clip.

[jbltecnicspro]

One last question - this is DC voltage right? I'm pretty sure it is but I want to be sure.


Edit: Okay nevermind, it's DC.

All tubes were max on bias and max on gain - no input was given

Blue: 501 volts

Green: 502 volts

Red: 568 volts

Double edit - no matter what I did to adjust the tubes the voltage measured at the G2 pins stayed the same. Red always hovered around 560 volts. Green and Blue were always around 500. This is with bias set to minimum and maximum - it didn't matter what I set it to.

[Curt Palme]

OK, try the GAIN control beside the bias. I may have gotten them backwards. It's still showing though that the output of the G2 levels to each tube are fine from the PA board, so we're back to a tube or a video problem. Had the green read down at 200-300 volts or so, then we'd have a PA board.. or control of the PA board.. issue.

[Curt Palme]

OK, try the GAIN control beside the bias. I may have gotten them backwards. It's still showing though that the output of the G2 levels to each tube are fine from the PA board, so we're back to a tube or a video problem. Had the green read down at 200-300 volts or so, then we'd have a PA board.. or control of the PA board.. issue.

[jbltecnicspro]