: Sony 57HW40 CRT RPTV: minor problem
2008-05-28, 06:38 PM
This TV is getting on, but the piccy is excellent still so don't want to landfill it just yet. Especially since what I want to replace it isn't very available right now in Canada, and the issue is more of an irritation than a complete failure.
What I'm seeing is some very light curved lines across the screen when the video level is very low. Noticeable in a dark scene that isn't ultra black. Happens for all inputs, at all resolutions up to 1080i.
I have the service manual. Has anyone seen something like this and know what it probably is? Is it something I can compensate for in the service menu? I ask that because if I adjust some of the TV picture settings (user menu) I can make the problem "go away", but these picture settings are unusable for me for actual viewing...so I'm thinking it may be something adjustable. The lines appear to be white, possibly light blue, certainly not red or green. There are maybe a dozen of them. It is definitely electronic rather than "dirt" on the optics etc., nor is it noise on the AC powerline. Thanks.
Curved lines on the screen may indicate that the convergence ICs or something in that circuit may be starting to go. See the following thread on the convergence issue that hits lots of older TVs and creates dramatic curved coloured lines.
I know your symptom is not identical, so this is pure conjecture.
2008-05-28, 08:06 PM
Thanks....that sure is a long thread! From what I read and saw in example shots, I don't think convergence is my problem. The picture does look excellent, this TV doesn't have a huge number of hours on it for its age. All the AVIA etc. test patterns look great, actually better than when the TV was new...Sony said the CRTs take ~1000 hours to be at their best (BTW these are Sony guns, not the [apparently better] Panny guns many of the later production models used). There is no distortion or bending lines or color misregistration etc. in the actual images. These faint lines are at a very low level, it takes very little picture brightness to obscure them. For instance, they are not visible when the TV user menu (black background) is onscreen.
I was hoping it might be a local PS cap or something simple like that...but which PS cap if it could be that. I was just guessing that because some signal level/threshold seems to not be holding up. I know it's hard to describe a problem, and this one would not photograph well it's so faint.
If these lines are sort of herringbone, or move a bit, then that's some sort of ingress. I've seen it before on a CRT and reducing the brightness a bit got rid of the problem. Some things to try:
- Reduce brightness and perhaps compensate with the contrast.
- plug TV into another circuit of the home - use an extension cord if necessary.
- plug TV into a UPS or good surge protector
- disconnect the various devices connected to the TV, one at a time, to see if it goes away.
Do you live in an older home? Does it have proper ground on this circuit?
- Try another circuit with proper ground?
You were pretty sure that it wasn't AC Noise - how were you sure?
2008-05-29, 08:09 PM
The lines are curved. I suppose it could be a very large herringbone, the lines are inches apart. What is "ingress"? Thanks.
Yes, adjusting brightness and contrast can make the lines go away, but the resulting picture is awful. I was hoping I could maybe adjust some threshold etc. in the service menu so I could leave the main contrast/brightness alone.
The lines are there with all inputs disconnected even. I plugged the TV into a balanced power supply for testing if it was AC line noise (normally I don't run the TV on BP because it will overload it with all the other stuff on it). I'll try the extension cord thing and some heavy duty filters too. MY HT AC wiring is a bit complicated, generally they are professional power products and not consumer stuff...so yes, I am a bit fussy about AC power (I work in it too, so I know how bad it can be...) and will check it out again.
Edit: I tried outlets all over the house using a 100' cord: no diff. The HT outlets are dedicated, and the wiring was done so that no noisy "automatic on-off" (fridge, freezer etc.) appliances are on that phase even. There are 8-9 lines on the screen, about 3" apart, slightly curved from the right downwards to the left, and I think they are light blue (not white). I am quite positive the problem is in the TV...this issue is not new, maybe started 6 months ago, and I forget all the "diagnostic" stuff I've done since so did it again to be sure... You can be sure I would ditch this TV if there was the slightest problem with the PQ, I can be a bit anal about things working 100% (engineer, anality rules...), but there isn't really, just this minor (I suppose) "aging" artifact which I have to wait until evening to diagnose because it's so faint, and it also isn't visible in most material... I am positive there are no focus/convergence/geometry-type problems.
Let me look through the service menu options in the manual and run some potential suspects by you to see if they could have any influence on this. I have gone into the SM a few times but never had the guts to actually change anything except turn off the individual guns (for some reason I forget). What I'm thinking of is first turning off the blue gun to see if no lines. If no lines, then I will adjust the B drive a bit, or some other B-only "harmless" parameter that doesn't have just an on-off option. If turning off the blue gun still gives the lines, then I'll try the other guns but if only one gun/circuitry is the problem, it has to be blue. Don't worry, I won't adjust anything I don't know what it is. I have lots of doc so have a good idea of what NOT to do, and have just enough knowledge to know what the problem can't be i.e. dangerous! I have absolutely no doc on fixing problems that aren't focus/convergence/geometry unfortunately.
2008-05-29, 10:51 PM
I was hoping it might be a local PS cap or something simple like that...but which PS cap if it could be that.On a normal CRT TV, capacitors would give you straight small cut lines but since you are using 3 guns to create each of the 3 colors (RGB) and since it seems to point out to blue, I would believe it could be capacitors specifically in the area of the Blue gun circuitry (thus the possible reason for curving as the capacitor problem would only show when Blue color is active). Do you own an ESR meter and do you know how to check for bad capacitors? Capacitors can be shortened, cold solder joints and even changed value (very common and an ESR meter could tell you that).
2008-05-29, 11:18 PM
^ That's kinda the sort of thing I was thinking it could be, and also maybe I could save myself some disassembly by first trying a few things in the SM JIC it was something a threshold/level tweak could minimise, or at least point to a circuit area. I will try to verify whether it is truly the blue gun tonight.
Yes I have an ESR meter. Did I mention I could be a bit anal about stuff working 100% ? :)
2008-05-29, 11:32 PM
Once you have disabled the Blue gun and potentially proven the problem is coming from it, check all caps with your ESR meter and replace anything that is not of proportional value. By the way, you should take the opportunity to check all caps as normally when some goes, many other ones are on the verge. Enjoy the trouble shooting challenge!
2008-05-30, 12:31 AM
Hmmm, so much for my idea: the lines are there with all the guns off. So we know it's something common to all inputs and all guns. Power supply?
2008-05-30, 01:08 AM
How did you turn your guns off? Software or hardware (unplugged)? If you turn them off by mean of your software programming, it doesn't mean you actually removing the entire circuitry. If you actually unplug the PCB from the tube you should have full results. When you disable your guns, you only get white raster on the screen? Yes, power supply could also be at fault as all voltages are provide from it... Faulty capacitors in the power supply could let some voltage or even AC pass through the guns circuitry.
2008-05-30, 01:27 AM
I only did it by software. Totally black screen, except for those pesky lines... I like the idea of some AC passing through the guns' circuitry...mainly because I understand it! :o I'm not too confident about messing around with the gun driver boards, or anywhere there might be HV, but don't mind looking at the main PS board(s). Was hoping to avoid opening the beast up, but after trying a bunch of things (too tedious to regale you with...) I'm leaning towards an electronic part having deteriorated. Especially towards an aging PS cap being fairly likely for this gradual/soft "failure". Thanks.
2008-05-30, 02:13 AM
Totally black screen, except for those pesky lines... Totally black then your guns are fully off, you do not need to do anything with those guns. HV is at the anodes of each tubes. This is really weird, you still see the lines with black screen, black screen means no white raster going to tubes. Has to be some juice going through from power supply, I mean black screen you should not see anuthing anymore. You have some electrons-current going through those tubes when it is not suppose too... very weird! never seen that before. How old is the TV again? Do you know if technology is surface mount or passthrough components? 7 to 10 years old would be a combination of both, right?
2008-05-30, 02:45 AM
I guess I should have said I turned the guns off in the service menu -> firmware...
The TV was built in late '01, I got it in Feb. '02. Since there's only me who watches it, and mainly DVDs on weekends, I'd guess it has 2500 power-on hours. From the stuff in the service manual, looks like a combo of techniques, larger stuff through-hole, most chips SMD.
Just want to reiterate that the lines are only visible with a low-level signal. It is quite annoying when watching just about any movie that takes part mostly at night...a few seconds of light lines here and there I can tolerate, but not all the time... Even a "strong black signal" makes the lines disappear...so the idea of "leakage" seems reasonable.
2008-05-30, 09:06 PM
Further looking shows it's definitely the Blue gun after all. With the TV back off and all guns turned off in the service menu, I could definitely see some light coming from it. I covered the B lens and the artifact lines disappeared. There is an item in the SM called "ALBK" and when I turn that off (it's binary, normally on) when the guns are all off (B not covered) I can see some very bright blue artifact stretching across the whole top of the screen, as well as those lines. Does this give you any more ideas? Thanks.
2008-05-31, 10:00 PM
Hmmm, guess you can't edit here after a certain amount of time, hate doing consecutive posts on the same thing... But wanted to finish the story JIC somebody had similar issues, this was a popular series of display.
Anyway, this is apparently a fairly common problem with all brands of CRT RPTVs and is usually very easy to fix *if this is all that is wrong*. And well-known in Sony TVs of this type typically when 3-5 years old. Mine probably took a tad longer because I didn't use it so much way back. It seems it's almost always the Blue gun that does this, much less commonly Green, almost never Red... My correspondence today suggests this issue is so common it is/was a bit of a service cash cow...it is annoying way out of proportion to what it is.
There is a pot you need to turn down (i.e. CCW) a very tiny bit. It's called the Screen/G2 control, on the Focus Board with 6 pots, and on this particular TV it's accessed from the front (you have to remove the speaker cloth panel thing, pretty easy to do). Do not touch the pots for Focus on the same board! You do not have to stick your hand in with a bunch of electronics. You (I) want the B one. This is easiest to adjust "just enough" if you turn off the CRTs in the service menu first i.e. with a "black" screen (RGBS = 0) and also set ALBK to 0 for good measure, but not necessary. Happy camper now!:p
2008-05-31, 10:49 PM
Good troubleshoothing cfraser. I hope this measure last you for a few good years of watching. However, the original symptom still point to wear and tear of some component. I figure the problem migth reappear later on down the road but I sure hope I am wrong.
As a note to anyone else reading this thread, the trimpots under discussion are extremely sensitive and if you get them too far out of adjustment, then you may never be able to get your greyscale back without a professional calibration.
2008-06-01, 01:02 AM
Thanks guys! BTW, I did not figure this out myself.
I am so pathetic, you don't know how truly happy I am about this itch of a problem being resolved.
And 57: that is absolutely true, I only had to breathe on the pot. They are painted with white junk, so I imagine you'd have to really torque on them to break it and get them to move much. I'd say I moved it 1° at most...can't even tell I moved it based on the mark I made beforehand.
Now to get the AVIA out and make sure the piccy settings are still decent.
2008-06-01, 01:35 AM
They are painted with white junk, so I imagine you'd have to really torque on them to break it and get them to move much.The "white junk" is actually "lock Tite" and is used for very sensitive adjustments that theorically should only be adjusted by a proffessional. Do not remove the "white junk" as it is a good reference to go back to if the set is not working the way you want anymore!