CurtPalme.com Home Theater Forum

[Curt Palme]

Hey, I'm working on a couple of Sony D50s. I haven't worked on a lot of them, so I'm throwing myself into these.

The problem on both of these is color balance, or lack thereof. Ditto with the abg control.

I need someone to tell me EXACTLY how the bias and gain controls work in their set.

I have the gain control on the one set I'm working on how acting like the contrast and G2 control at the same time. The bias control does NOTHING. This can't be normal. I thought the bias control set the black level on the set, and the gain control set the white levels (contrast)? THis set isn't working like this.

I have found one bad neck board, when I use the green tube cutoff control (to turn the tube off), the other two tubes go brighter. THe R and B cutoff switches don't do this. Putting in another green neck board cures this, but doesn't cure the lack of bias action.

I do have a number of A boards, some that have separate G2 adjustments in the software, some that don't.

So.. can someone tell me their bias and gain levels, and what exactly happens with the gain and bias controls both with the abg setting on and off.

Once I have a better understanding of what they are supposed to do, I'll be able to troubleshoot these chassis better.

Thanks!

[Curt Palme]

Hey, I'm working on a couple of Sony D50s. I haven't worked on a lot of them, so I'm throwing myself into these.

The problem on both of these is color balance, or lack thereof. Ditto with the abg control.

I need someone to tell me EXACTLY how the bias and gain controls work in their set.

I have the gain control on the one set I'm working on how acting like the contrast and G2 control at the same time. The bias control does NOTHING. This can't be normal. I thought the bias control set the black level on the set, and the gain control set the white levels (contrast)? THis set isn't working like this.

I have found one bad neck board, when I use the green tube cutoff control (to turn the tube off), the other two tubes go brighter. THe R and B cutoff switches don't do this. Putting in another green neck board cures this, but doesn't cure the lack of bias action.

I do have a number of A boards, some that have separate G2 adjustments in the software, some that don't.

So.. can someone tell me their bias and gain levels, and what exactly happens with the gain and bias controls both with the abg setting on and off.

Once I have a better understanding of what they are supposed to do, I'll be able to troubleshoot these chassis better.

Thanks!

[AnalogRocks]

Sounds like you are having some of the same problems I am. If I mute either of the other two tubes the raster on the blue light's up and my brightness control doesn't seem to do much. We were talking about that here

Seem's these set's are having control difficulties. They're not as robust as the 12xx series.

[AnalogRocks]

Sounds like you are having some of the same problems I am. If I mute either of the other two tubes the raster on the blue light's up and my brightness control doesn't seem to do much. We were talking about that here

Seem's these set's are having control difficulties. They're not as robust as the 12xx series.

[Curt Palme]

Well I found the problem for that changing brightness when you mute one tube, it's a bad neckboard. I'm now working on the streaking issue on that same neckboard.

Seems like some of the flaws of the D50 are now coming out of the woodwork. Not a big deal really, but I need to get to the bottom of this. I finally have one decent set of D50 tubes so I need a fully working set.

I'm about to order a mass of parts for these D50s to get the neckboards 100%. Send me yours if you want and I'll repair it. THe one that is bad is the one that causes the other tubes to go brighter when you turn it off. There should be no brightness fluctuation when yo cut one tube off. At least that's what I've found so far. It's D50 day today apparently..

[Curt Palme]

Well I found the problem for that changing brightness when you mute one tube, it's a bad neckboard. I'm now working on the streaking issue on that same neckboard.

Seems like some of the flaws of the D50 are now coming out of the woodwork. Not a big deal really, but I need to get to the bottom of this. I finally have one decent set of D50 tubes so I need a fully working set.

I'm about to order a mass of parts for these D50s to get the neckboards 100%. Send me yours if you want and I'll repair it. THe one that is bad is the one that causes the other tubes to go brighter when you turn it off. There should be no brightness fluctuation when yo cut one tube off. At least that's what I've found so far. It's D50 day today apparently..

[draganm]

I don't mean to throw in negative stuff into this thread but I thought you really didn't like these sets and didn't think they were worth bothering with? IF so, I have to agree with you. I imagine you are getting requests from customers for repairs on these but with so many G70's on the secondary market it seems like that would be a much better place to invest time and money. Performance wise, the G70 and D50 are so far apart it doesn't make any sense to bother with the D50's, their $800. tubes, and barely 1080i perfromance.
AFA the problems your desrcibing, a local guy here wound up totally by-passing the g2/bias controls in the set and adding an external block with trim pots. That cleared up the problem right before he got rid of it and switched to an 8" EM set.

[Curt Palme]

Well there is that, but I'm on a mission since I have a decent set of tubes here. The way I see it, the set worked from the factory just fine, now I want to see why they are acting up. I'm slowly working through it. There's a feedback loop between the tubes and the G2/gain/bias circuit. I'm slowly narrowing it down...

So I could bypass it (and actually just did while troubleshooting), but that's why I know all of the other sets so well, I stuck with it until I repaired them. So far I've found the cause for a streaking problem as well...

[Curt Palme]

Well there is that, but I'm on a mission since I have a decent set of tubes here. The way I see it, the set worked from the factory just fine, now I want to see why they are acting up. I'm slowly working through it. There's a feedback loop between the tubes and the G2/gain/bias circuit. I'm slowly narrowing it down...

So I could bypass it (and actually just did while troubleshooting), but that's why I know all of the other sets so well, I stuck with it until I repaired them. So far I've found the cause for a streaking problem as well...

[drice1234]

Do you think that this will be the fix for the low brightness problem with the D50's? I still have one in the attic with this issue. You (Curt) have already repaired the PA board but this did not take care of the problem.
Thanks, Dan

[Curt Palme]

OK, I've sorta solved it.

Unless someone wants to prove me wrong, the bias controls do almost nothing on the D50. I was expecting the bias controls to have a significant effect as on a Sony 12XX series.

The problem I was having was that brightness/G2 levels were all over the place on this set. Color tracking was horrible as well..

Here's my theory of operation. I could be slightly off on this, but this is what it's taken me all day to figure out:

As with other sets with abg/AKB circuits, there's a loop formed in the set that senses tube emission and feeds that info back to the A board where it sets the bias(G2) of the set. On these sets, the abg needs to be in the ON mode. If it's off, the G2 parameters can be all over the place. I was thinking that normal operation is in the 'off' mode, but the install manual that I just dug out clued me in to being incorrect.

Now, this set seems to work similarly to the Zenith PRO 851. You won't get decent white balance if you mix old and new tubes. The gains of the individual tubes will be a mile off from each other, and that throws the D50 off. Same with the PRO 851. Put in one tube with low or high emission compared to the others, and you'll get a white balance that's all over the map.

TO further confuse things, a bad PA board or a bad neck board will really throw off the abg circuit. I had that in this set as well. Once the abg circuit gets confused, the white balance is off and the G2 voltages on the neck boards can be way off as well, since every drive signal comes from the A board.

I got even more confused when I turned the abg on and off. THe white balance was again all over the map, but to the point where one tube would be off completely. In my case the green tube would turn off, giving a purple pix.

As with the G70, the older software version of the D50 is much preferred. That gives independent control of the G2 voltages by pressing the bias button twice. That gets you into the G2 menu. I dropped in an A board with variable G2 adjustments, and all of a sudden the set started looking pretty good with the abg on. Then I could finally see the pluge pattern when I went into the bias mode, and found that while the bias adjustment did have SOME effect on the image, it really was minimal, and only in the 100IRE range.

I then pulled out the older A board and put in a newer style, and still got pretty good white balance once I set the gain controls, but not quite as good as with the older board.

One tip that I'll share to find a bad neck board is to fire the set up, and then carefully pull the mini video connector that feeds the video signal to the neck card. Pull the connector off at the neck card with an image showing and abg on.

If the brightness level of the other two tubes shifts massively or even to a minor degree, the neck board is defective. You can also do a similar thing with the tube cutoff switches, but I found it to work better by pulling the video feed.

So Dan, to answer your question, if anyone wants me to repair a low brightness problem on a D50, I will now tell them to send me the A, PA and all three neck boards. All are easy to take out, but you need to flip out the focus control panel to access the thick red focus leads that plug into the back of the focus block. 3 screws unscrew it. You can't pull it out all the way due to the wiring, but you can get it out enough to access the focus leads on the back of it.

Since I have a D50 set up now, I'll take a bunch of pix to do a writeup on the main site. I'll add this brightness problem troubleshooting to the main site, since it's one of the most common D50 problems.

I also have a messload of D50 parts from various sets scattered around the bench. I'm about to test each one to make sure they all work in a working set, but bottom line is, multiple problems in the one set compounded by a slight techy user error (abg being off) resulted in a bunch of work for me today.

But hey, I can tell you just about where every component for the abg is located on the A, PA and neck boards..

[Curt Palme]

OK, I've sorta solved it.

Unless someone wants to prove me wrong, the bias controls do almost nothing on the D50. I was expecting the bias controls to have a significant effect as on a Sony 12XX series.

The problem I was having was that brightness/G2 levels were all over the place on this set. Color tracking was horrible as well..

Here's my theory of operation. I could be slightly off on this, but this is what it's taken me all day to figure out:

As with other sets with abg/AKB circuits, there's a loop formed in the set that senses tube emission and feeds that info back to the A board where it sets the bias(G2) of the set. On these sets, the abg needs to be in the ON mode. If it's off, the G2 parameters can be all over the place. I was thinking that normal operation is in the 'off' mode, but the install manual that I just dug out clued me in to being incorrect.

Now, this set seems to work similarly to the Zenith PRO 851. You won't get decent white balance if you mix old and new tubes. The gains of the individual tubes will be a mile off from each other, and that throws the D50 off. Same with the PRO 851. Put in one tube with low or high emission compared to the others, and you'll get a white balance that's all over the map.

TO further confuse things, a bad PA board or a bad neck board will really throw off the abg circuit. I had that in this set as well. Once the abg circuit gets confused, the white balance is off and the G2 voltages on the neck boards can be way off as well, since every drive signal comes from the A board.

I got even more confused when I turned the abg on and off. THe white balance was again all over the map, but to the point where one tube would be off completely. In my case the green tube would turn off, giving a purple pix.

As with the G70, the older software version of the D50 is much preferred. That gives independent control of the G2 voltages by pressing the bias button twice. That gets you into the G2 menu. I dropped in an A board with variable G2 adjustments, and all of a sudden the set started looking pretty good with the abg on. Then I could finally see the pluge pattern when I went into the bias mode, and found that while the bias adjustment did have SOME effect on the image, it really was minimal, and only in the 100IRE range.

I then pulled out the older A board and put in a newer style, and still got pretty good white balance once I set the gain controls, but not quite as good as with the older board.

One tip that I'll share to find a bad neck board is to fire the set up, and then carefully pull the mini video connector that feeds the video signal to the neck card. Pull the connector off at the neck card with an image showing and abg on.

If the brightness level of the other two tubes shifts massively or even to a minor degree, the neck board is defective. You can also do a similar thing with the tube cutoff switches, but I found it to work better by pulling the video feed.

So Dan, to answer your question, if anyone wants me to repair a low brightness problem on a D50, I will now tell them to send me the A, PA and all three neck boards. All are easy to take out, but you need to flip out the focus control panel to access the thick red focus leads that plug into the back of the focus block. 3 screws unscrew it. You can't pull it out all the way due to the wiring, but you can get it out enough to access the focus leads on the back of it.

Since I have a D50 set up now, I'll take a bunch of pix to do a writeup on the main site. I'll add this brightness problem troubleshooting to the main site, since it's one of the most common D50 problems.

I also have a messload of D50 parts from various sets scattered around the bench. I'm about to test each one to make sure they all work in a working set, but bottom line is, multiple problems in the one set compounded by a slight techy user error (abg being off) resulted in a bunch of work for me today.

But hey, I can tell you just about where every component for the abg is located on the A, PA and neck boards..

[redcorvette_85]

Hey Curt,

Have you ever run across a D50 that has focus issues? I have one with pretty good tubes, but it will go in and out of focus at times, used to be just every once and awhile, now its pretty common. It will be really sharp, then the text and such will get blurry for awhile then go back. Seems to get worse the higher the signal I put into it, less problems at 1080i and more frequently at 720p. Haven't cared much since I have better projectors to replace it with once I find the right lenses and I just need to get rid of it, but I am curious.

Thanks

[Curt Palme]

That's most likely the focus block with teh controls on it. Can you make it to the Tulalip casino tomorrow by about 7? I'm heading there for a KISW party and will be there by 5:30. I can bring another one with me if you want.

[Curt Palme]

That's most likely the focus block with teh controls on it. Can you make it to the Tulalip casino tomorrow by about 7? I'm heading there for a KISW party and will be there by 5:30. I can bring another one with me if you want.

[redcorvette_85]

Thanks for the offer Curt, but theres no way I could make it there anywhere near 7 with the job site I am on tomorrow and traffic. I may pick one up from you some other time though if I find a good home for the projector one day. Nice to know whats wrong with it though, Thanks

[AnalogRocks]

Wish I had noticed this before I gave it to my G/F. If I take away her 3 week old projector she'll probably not talk to me...wait a second....isn't that a good thing?

[AnalogRocks]

Wish I had noticed this before I gave it to my G/F. If I take away her 3 week old projector she'll probably not talk to me...wait a second....isn't that a good thing?

[Curt Palme]

Email me to remind me. I'll just send you new neckboards. I have tested ones here now..

[Curt Palme]

Email me to remind me. I'll just send you new neckboards. I have tested ones here now..