Slight Blue Tint with Color Down
 

I picked up a lightly used Panasonic set (CT-20S10S) with the same chassis as mine (CT-20S2S) as a potential replacement CRT. They are the same TVs, except the new one has composite input. They have the same remote and menus.

My old CRT is a little tired, with slight burn-in from closed captions and a slightly dim top right corner. With color all the way down, the image is black and white, maybe a very very slight green tint (maybe).

On this new one, there are no dim corners, no burn-in, and the image is significantly brighter and a little sharper.

However, with color all the way down, the new one has a slight blue tint. What is the reason for this? I can't imagine it's more worn than the old one, which doesn't have a tint with color down. Is this how the set was when new?

If you have darkening on one side, check the 4.7mfd 315 cap on the CRT board or nearby. :scratch2:

Slight tint of color with color control minimum probably just means it needs a slight color tracking adjustment.

Even on a 1994 TV? That would probably be in the service menu.

Ooops - mixed up my threads - sorry

So how do I adjust the color tracking? Watching a black and white movie reveals the slight blue tint as well.

Sorry, maybe someone else here knows how to find the service info or access the service menu if that's what it takes.

Here is what the service manual says.

https://uz6wxq.by.files.1drv.com/y4m...&cropmode=none

This is a little overwhelming. Which of these settings controls tint (regular menu tint has no effect)? How do I jump FA1 and FA2?

You do not want any of the DAC (B) mode adjustments. You want the CRT (C) mode adjustments. Do you have a page showing them and telling their names?

Do you have a diagram showing the location of FA1 and FA2? Are they close enough to bridge with a screwdriver, or do you need a wire/jumper wire with alligator clips?

Yes, here is the location of FA1 (N/2) and FA2 (N/3). Looks like they are down by the tuner. I will take off the back, jump them with alligator clips, then turn the set on and follow the directions to enter serviceman mode.

https://mioxoa.by.files.1drv.com/y4m...&cropmode=none

Are you referring to this table?

https://zz6pqg.by.files.1drv.com/y4m...&cropmode=none

Thank you for the help. I want to carefully do this adjustment because I like the TV.

Yes, that table. Follow the instructions for C1 through C5 to get rid of any tint to the monochrome picture.

Will do. Thanks so much.

Is there a good test pattern to use for color tracking adjustment? I have a video essentials DVD somewhere.

A gray scale (steps) is best; color bars with the color turned all the way down works too, or you can even do it with regular programming with the color turned all the way down. (I don't know if your set automatically turns the color down when you are in CRT adjustment mode, but that would make sense.)

As the instructions state, go for a gray picture with no noticeable tint.

Off to bed now - good luck

I'll report back with results! Thanks!

I just tried it. When I first got into service mode, the values were as follows.

I set them to the default values listed in the service manual.

Not only is the weird blue tint completely gone, the image is spectacular compared to before. MUCH brighter, I had to set brightness and picture way down before I was comfortable with it.

Am I good? Picture looks great.

The differences in C1, C2, and C3 had to be compensating for the old tube's cutoff values. Setting them to equal default values with good results indicates that the new tube's guns are much more balanced.

If there is no problem with the picture , I'd call it good. :thmbsp:

By the way, what test pattern or image did you use?

I didn't use anything. I just set everything back to the default values and the image looks great now with everything. I calibrated picture and brightness to 7.5 IRE and 0 IRE.

The only problem left is that it's always had a small color problem where the outline of bright objects, like red and green, have a magenta outline to the left. Here's a photo of a bright red object. Looks like red starts a little late drawing from left to right. Is this convergence?

https://woxaig.by.files.1drv.com/y4m...&cropmode=none

This doesn't occur on the old TV, which is the same TV as this one but with a tired tube.

Are you suggesting the tube was replaced at some point?

Convergence problems manifest as a color fringe on a white line on a black background...if it doesn't do that then it is not convergence, but more likely a video/IF issue.

No problems with white lines. What is IF?

I misunderstood - thought you were talking about new tube in old TV.

Regarding the color fringe, it's convergence only if it's there with the color turned all the way down.

If it appears only when the color is turned up, it's something in the phase response; IF alignment, chroma alignment, fine tuning. Whether it's a problem depends on how strong it is. Analog sets are seldom completely free of this.

IF = Intermediate Frequency
Alignment involves aligning the Radio Frequency (RF) circuits in the tuner and the IF circuits in the IF amplifier. It must be done with an alignment generator and oscilloscope; cannot be done by eyeballing the picture.

Ah, I see. No, I just have two, my original and the new one. They are 99% identical from the same production run. The old one I've had for years is simply getting tired, so when I saw the new one pop up for free a year or so ago I grabbed it. The new one looks like it was used much less, but had this weird tint issue.

If I turn color all the way down, the fringe is still there, everything just becomes black and white. I'll take a photo when I get a chance, as well as with some white lines.

You must be a gamer as that's a play station logo. My personal recommendation is to enjoy the set as is. It doesn't sound like you have much in the way of tv test equipment. You have that logo pretty zoomed in and I can see it's not a convergence issue. Guessing that tv is from the nineties or late eighties. A CRT set can never be compared to a modern HD tv but for what there technology was it was very adequate for its time. Sit back and enjoy it. Glad you got the color balance adjusted.

Good eye. Not really a gamer, the Playstation came with the TV for free, along with some games. The intro logo is a very good example of the fringe though, due to the stark red on black. I'm probably going to sell or donate it.

Correct, the TV was manufactured in November 1994. The reason I brought up the fringe is because I have the same TV (manufactured in July 1994) and while it has a very tired tube, which was the reason I picked the second one up, it doesn't have the fringe, which makes me think it's an adjustment issue.

Is the issue intermediate frequency?

No problem there. :) The old TV I've had since new, though my dad bought it. I am very cheap (and a poor student) so I hung onto it all these years, fixing little issues here and there. I simply wore out the tube, so when a second one popped up (for free), I couldn't resist continuing the legacy. Besides, I work a lot so I don't really watch much TV.

I guess you could say I like this model line from Panasonic.

Here is a photo of a basic grid of white lines.

Is the color level set to min in that picture? I see red dots parallel to the line that look like some sort of IF or video stage noise/ringing issue being decoded as color dots...If it weren't for those dots it would almost look like miss convergence (though I'm pretty sure it is some sort of video ringing effect).

goofy idea: If you still have the set with the weak CRT maybe try swapping the main PCBs between the two sets. Maybe the board from your old set will drive the CRT without that ringing artifact. Be sure HV is discharged before unplugging the HV lead.

That was with color normal. Here is color normal, then color at 0 for the same spot.

I see all three colors on the original line and the echo so convergence is ok?

I do wonder why the service settings were so messed up. Maybe someone was there before me. Looks like blue cutoff was way up for some reason. I also wonder if the default cutoff values being much higher (128 vs 90s) will negatively impact the tube.

Probably unrelated, but the set also has an occasional quiet popping noise through the speakers.

Your convergence is decent. What you have is ringing in the monochrome channel that is also being decoded into color noise creating a faux convergence error.

That's good, I'll just leave it.

The occasional popping noise I suspect might be a capacitor in the video detection circuit, because I noticed that when video is disconnected (RCA connector unplugged), audio mutes as well. Also, the pop doesn't occur in RF mode.