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 Post subject: Fixing black crush on Sony KV-21FX30E
PostPosted: Sun Sep 06, 2020 9:15 pm 


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This Sony CRT TV has much better geometry, linearity, convergence and less blooming than my other Trinitron and I quite like it. I tweaked the geometry in the service menu, pretty good!

One thing I noticed compared to my other Sony is quite a bit of black crush. I tried tweaking the normal contrast & brightness settings first, not a lot of success. Contrast does not affect it at all. Brightness fixes it if I turn it up to 75-85%, but anything more than say 55% raises the black level way to much. Basically a completely black screen will look grey on brightness 65%. In general the contrast and brightness controls seem to behave very differently on this set compared to other Sony's I've seen. I never tweaked any of the color / picture related settings in the service menu, maybe there's something I could do there? Like some kind of gamma boost vs just brightness might help bring out darker shades without making blacks grey?

Service manual & relevant settings:

Image

https://www.manualslib.com/manual/15956 ... fx30b.html

Thanks for any advice!


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 Post subject: Re: Fixing black crush on Sony KV-21FX30E
PostPosted: Mon Sep 07, 2020 2:39 am 



Joined: 23 Aug 2020
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Do you have an option for Y-DC? I had problems with black crush on my KV27S42 until I set this option to 0.


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 Post subject: Re: Fixing black crush on Sony KV-21FX30E
PostPosted: Mon Sep 07, 2020 5:06 am 


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Look for a setting called "black stretch". I'm not sure if it was a thing on Sony's, but on other TV's it was basically a mode that crushed blacks to fake higher contrast.


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 Post subject: Re: Fixing black crush on Sony KV-21FX30E
PostPosted: Mon Sep 07, 2020 9:30 am 


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Hm, I don't see anything like that. Look at the picture I posted, those are the relevant service menu options I think. This should be everything relevant from the service manual I linked:

Image
Image
Image

Anything here look useful?


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 Post subject: Re: Fixing black crush on Sony KV-21FX30E
PostPosted: Mon Sep 07, 2020 8:08 pm 



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This isn't all that uncommon with some post 2000 crt's. It's usually not a problem for any of the older systems but on consoles like the PS2 or Gamecube one can potentially see black crush. The solution is what you tried, pushing brightness and sub brightness (contrast on modern tv's), but if you really push it too much you can end up having side effects as you say, on some sets this might be blacks turning grey, or on other sets video anomalies like interference appearing. In my experience the problem is most present with horror games on the PS2/GC, and many of them offer ingame contrast adjustments in the settings or options, so that's the next thing you can try if your set isn't cooperating.

If you ever find another remedy I'd love to know too.


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 Post subject: Re: Fixing black crush on Sony KV-21FX30E
PostPosted: Mon Sep 07, 2020 9:45 pm 


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You're right, I can't really see it with Famicom / Master System games, but it's quite noticeable on XBox games.

The issue with the normal menu settings is that there's really not much I can do. Contrast has no effect on the black crush and brightness has no useful sweet spot. Basically as soon as I go over 50% blacks start to wash out and the entire thing starts to look like a crappy LCD. But I really notice black crush in xbox games. For instance in Outrun 2 right at the beginning there's a sky scraper where you can see the side facing away from the sun, and it's just a black slab. On my LCD + OSSC or my older Sony set you can clearly see the windows etc. To get the same shadow detail on the FX30 I have to turn up the brightness to like 70-80% which completely washes out all blacks. And it's not like the tube itself is bad, the TV gets very bright and has good blacks. It's like one of those dumb 'Black Enhancer' settings on modern TVs.

Is there anything in the service menu I should play around with? What exactly is 'sub contrast' / 'sub brightness' etc.?


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 Post subject: Re: Fixing black crush on Sony KV-21FX30E
PostPosted: Mon Sep 07, 2020 11:49 pm 



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Sub-contrast and sub-brightness are used to set the value of the Contrast/Picture/White Level and the Brightness/Black Level when the user adjustable picture controls are set to the middle of their range. This ensures that there's an adequate amount of adjustment room in either direction to correct sub-optimal signals. Unless you've already got the user controls set to min/max, adjusting the sub- controls in the service menu won't yield better performance.

Additionally, CRTs in production environments weren't adjusted for the deepest blacks possible; the black level was set with a PLUGE to ensure that no shadow detail was visibly crushed. When the PLUGE is set correctly, there's a good chance that the black level will be elevated from the absolute minimum luminance the display is capable of.

EDIT: One thing to consider as well is that most CRTs have a flat power law gamma of anywhere from 2.3-2.5, whereas modern LCDs at least try to conform to BT 1886, resulting in a gamma curve that decreases toward minimum luminance in order to ensure that shadow detail isn't crushed. A low-end gamma of 2.5 could very much look like black crush compared to a low-end gamma of 2.0, for instance.

EDIT 2: Poynton's article on adjusting brightness and contrast may prove useful: https://poynton.ca/notes/brightness_and_contrast/index.html. It sounds like your display may be trying to do some kind of dynamic contrast but none of the available service menu options look like what I've used to defeat such things on other models.


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 Post subject: Re: Fixing black crush on Sony KV-21FX30E
PostPosted: Tue Sep 08, 2020 2:14 pm 


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Thanks for your links and explanations. I agree, it looks like the gamma is to high on this set. And contrast & brightness are just linear adjustments, so they'll never actually fix this issue. What I'd need is either directly adjusting the gamma or some kind of log() shaped boost to counteract the fall-off from the high gamma.

Did you look at some of the settings available in the 'TEST MODE 2' menu? Here:

Image

There's some kind of AGC (automatic gain control?) adjustment, something about the G2 voltage (related to black level?), velocity modulation (related to contrast?).

The black crush is the only thing really wrong with this TV. Geometry is quite good for a flat CRT:

Image

Left side is a little pinched vertically, wish there was an adjustment like 'Pin Phase', just vertically, but well, it's already damn good IMHO.

The black crush is unfortunately quite visible in real games, here's the aforementioned sky scraper at 50% and 100% brightness.

Image
Image


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 Post subject: Re: Fixing black crush on Sony KV-21FX30E
PostPosted: Tue Sep 08, 2020 7:51 pm 



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Yeah that's some real black crush. I like reading this thread, I hope you find the solution.

Geometry looks great on that set. Maybe it was calibrated at some point. Contrary to popular belief, flat crt's can achieve just as good edge and corner geometry as curved, it just sometimes requires some work, yours doesn't though.


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 Post subject: Re: Fixing black crush on Sony KV-21FX30E
PostPosted: Tue Sep 08, 2020 9:39 pm 



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I haven't encountered any Sonys where Automatic Gain Control was related to picture settings; normally it's related to over-the-air reception or to automatic volume leveling. Velocity Modulation is essentially a form of edge enhancement and shouldn't impact black levels. Your geometry is as close to perfect as I've seen on a consumer TV set of that size.

On my KV27S42, the brightness and contrast are noticeably affected by which label is selected for the AV input (varies between AUX, GAME, DVD, DTV, WEB). If you have the option of selecting an input label from the user controls, I would try that. Given that everything else about the set is so good, I would hesitate to make too many adjustments in the service menu.


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 Post subject: Re: Fixing black crush on Sony KV-21FX30E
PostPosted: Tue Sep 08, 2020 11:52 pm 


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Taiyaki wrote:
Geometry looks great on that set. Maybe it was calibrated at some point.


Took me like 45min in the service menu, was quite pleased that nearly all defects were fixable with the provided adjustments!

GrimShins wrote:
I haven't encountered any Sonys where Automatic Gain Control was related to picture settings; normally it's related to over-the-air reception or to automatic volume leveling. Velocity Modulation is essentially a form of edge enhancement and shouldn't impact black levels. Your geometry is as close to perfect as I've seen on a consumer TV set of that size.


Ok, I wish there was some good wiki/FAQ about all this stuff, the service manual and random google searches don't really have much useful info on a lot of these settings.

GrimShins wrote:
On my KV27S42, the brightness and contrast are noticeably affected by which label is selected for the AV input (varies between AUX, GAME, DVD, DTV, WEB). If you have the option of selecting an input label from the user controls, I would try that. Given that everything else about the set is so good, I would hesitate to make too many adjustments in the service menu.


Really good idea, but it doesn't seem to work on my set :/ I have an 'AV Preset' option in the setup menu where I can assign labels like GAME or VIDEO to the three inputs, but it doesn't seem to change anything. It seems to set the labels and show them in the info display, but I didn't see any immediate change in the picture. I tried turning the TV on and off, didn't seem to look different. There are also picture modes like 'Live' & 'Movie', but from what I can tell they simply set Brightness/Contrast/Color to some fixed values.

I wonder if maybe this could be related to PAL vs NTSC. I've read that some Sony PAL TVs only show or save certain settings when connected to a PAL source. And I remember reading that NTSC-J consoles have a different black level or something. So far I've only tested the TV with my NTSC flashed OGXB over SCART RGB and my A/V modded Famicom over composite.


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 Post subject: Re: Fixing black crush on Sony KV-21FX30E
PostPosted: Thu Sep 10, 2020 2:30 pm 


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So, I decided to try hooking my NTSC PSone to the TV. The only 240p testsuite I tried before was on the Famicom and that machine has to few colors to even display a meaningful grey ramp. To my surprise there doesn't seem to be any black crush with the PSone. Also something odd is that on the Famicom I can't get the PLUGE dialed in properly (either washed out blacks or black crush), but in the IRE test screen the darkest '0 on -12' shows up correctly while it's all black on my other set. Hm. Basically:

- NTSC-J Famicom with 240p testsuite is a wash between the FX30E and other screens, certainly no problems I can see in-game
- PAL-to-NTSC modded Master System looks perfect in-game, don't have access to 240p testsuite
- NTSC-M PSone looks perfect
- PAL-region OGXB softmodded to NTSC-M video BIOS has severe black crush

Hm, so only really the xbox. Luckily most xbox games have a brightness slider etc. Maybe it is an NTSC-M vs NTSC-J vs NTSC 3.58 vs NTSC 4.43 type issue. Oddly enough my older Sony has a 'Gamma' setting in the service. WTF Sony, I needed that, don't remove stuff :-)

But really, I'm very happy with this TV, for free + 15min drive, A+, would pick up again.

btw, what exactly is this G2 adjustment option in the service menu? Been a bit scared about messing with it, but it is related to the tube's black level?


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 Post subject: Re: Fixing black crush on Sony KV-21FX30E
PostPosted: Thu Sep 10, 2020 8:20 pm 



Joined: 04 Apr 2014
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Yes this issue is common on the PS2/Xbox and Gamecube. The best I do is to push the brightness (contrast) setting up a few points when using those systems, and then dial it back to the normal preferred setting.

Someone else will surely explain G2 better than me as I'm not familair enough with it. I wouldn't touch it though. I have made adjustments to it in the past using a the solid patterns was was recommended and it only made things worse. In one case I had the tv develop lines that would appear on certain backgrounds, like refresh lines of sorts, as if the screen cycling of the crt was thrown off.


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 Post subject: Re: Fixing black crush on Sony KV-21FX30E
PostPosted: Fri Sep 11, 2020 3:42 pm 


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Seems like something I'd rather not mess with, thanks for the explanation.

It's just a little frustrating that my older set without black crush issues has a functional gamma setting that seems to do exactly what I'd expect it to do while my newer Sony with black crush has no such thing. Ah well, I'm still very happy with my new TV :D


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 Post subject: Re: Fixing black crush on Sony KV-21FX30E
PostPosted: Sat Sep 12, 2020 3:38 am 



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That's the thing with crt's. It's like they all have their own quirks. I went through endless models before finally finding the ones I liked best (they still had quirks too though). Some people rush to say recap needed, or bad boards, but that's more often than not not the case (generally easily proven by having multiple of the same models recreating the exact same behavior). None of these tv's are perfect regardless of what some users might say about their own preferred set, it's just the way of the crt's. :D


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 Post subject: Re: Fixing black crush on Sony KV-21FX30E
PostPosted: Sat Sep 12, 2020 12:49 pm 


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Yep, it seems the only way is to keep picking up CRTs in your area and then pass on the ones that you don't want. This TV is my 3rd major upgrade.


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 Post subject: Re: Fixing black crush on Sony KV-21FX30E
PostPosted: Mon Sep 14, 2020 9:42 am 



Joined: 17 Mar 2018
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Wow, your Geometry looks nice!

I briefly had the 29 inch version of this set (29FX30E, also with FE-2 chassis), but its geometry was so bad that I had to do a yoke reseat. Even after that, the horizontal linearity was too distracting and I got rid of it.

There's a 21 inch set in my city right now for 1€ but I try to stay strong and not pick it up. But your post doesn't make it easier :mrgreen:


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 Post subject: Re: Fixing black crush on Sony KV-21FX30E
PostPosted: Mon Sep 14, 2020 12:35 pm 


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I'll probably fiddle with the linearity a bit more at some point. Horizontal scrolling is almost perfect but I can see a bit of stretching/compression at the top of the screen for vertical scrolling games.

Right now i can locally see a 29FX30E, another 21FX30E a bit further away and some other 21" FE-2 screen, but a lower-end model with less inputs etc. From my small sample size I'd say larger screens generally have more issues?

How's the convergence on your sets? I've never had a CRT where not at least a couple of borders/corners had color divergence. Mostly it's red. Can always see some red fringing on white text etc. It's a lot more noticeable in 240p content vs 480i since it bleeds into the scanlines. Like red areas have thick scanlines but white spots have red bleeding into the scanlines.


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 Post subject: Re: Fixing black crush on Sony KV-21FX30E
PostPosted: Tue Sep 15, 2020 8:18 am 



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Yeah, unfortunately you can't really do much to combat bad horizontal linearity. It tends to be worse on flat trinitron tubes in my experience. Also on bigger sets.
Almost all of my consumer sets have some convergence errors or a sagging corner here and there, but I've come to accept these small flaws in general. Tube technology just does not shine when it comes to convergence and linearity, but most people nowadays that come from LCDs kind of assume that every consumer set can achieve perfection in these areas which is not the case.

Even on my pro monitors it's not all perfect. I have a 20M2MDE with convergence and focus issues in one corner. Sometimes you just have to settle for "good enough" I guess.


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 Post subject: Re: Fixing black crush on Sony KV-21FX30E
PostPosted: Tue Sep 15, 2020 10:23 am 


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To be fair, this seems to be mostly a TV and not a general CRT problem. I distinctly remember that my PC CRTs had adjustable convergence for each corner separately and you could in general adjust and fix basically any blemish. I think tubes itself can be 99% perfect, but for TVs they did not want to spend the money to add all these digital adjustments for the geometry, focus, convergence, color etc. and then calibrate it at the factory. Most of this is hardly noticeable on typical 480i video material, so probably not much of an issue to the average TV & movie watcher.


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 Post subject: Re: Fixing black crush on Sony KV-21FX30E
PostPosted: Tue Sep 15, 2020 12:46 pm 



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Yes, this is true! It's amazing what control you have with newer Sony monitors and WinDAS, for example.


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 Post subject: Re: Fixing black crush on Sony KV-21FX30E
PostPosted: Tue Sep 15, 2020 1:59 pm 



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ASDR wrote:
I'll probably fiddle with the linearity a bit more at some point. Horizontal scrolling is almost perfect but I can see a bit of stretching/compression at the top of the screen for vertical scrolling games.

How's the convergence on your sets? I've never had a CRT where not at least a couple of borders/corners had color divergence. Mostly it's red. Can always see some red fringing on white text etc. It's a lot more noticeable in 240p content vs 480i since it bleeds into the scanlines. Like red areas have thick scanlines but white spots have red bleeding into the scanlines.


You refer to the distortion that looks like the picture scrolls over a pencil (stretching in and back out)? If so I have yet to see a single CRT that doesn't do that on some part of the picture. It's usually not something that any setting (yoke or otherwise) can alter. I have no idea what the exact term is, but I had it on both BVM monitors too, and every PVM I've seen too). My best consumer crt's have it in much less pronounced ways but in more sections of the screen but in smaller degrees, so things feel more evened out if that makes sense (vs having one terribly noticeable warping spot).

Yes bigger screens tend to have both worse geometry and convergence. The middle sized tv's at 20 and 24 inches seem to be the cutoff point where these two get worse very fast for each size up, at least that's my experience, but I lost interest in 27 inch and up tv's a long time ago now.

Convergence on the corners/edges is never expected to be good, usually it's red or blue that stands out. Some people manage to get good corners but generally at the expense of the geometry, it's usually an either or, or a compromise, whichever you find most agreeable. I tend to favor geometry myself as geometrical lines being thrown off at corners or edges draw my eyes more to it than some convergence color issues would.


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 Post subject: Re: Fixing black crush on Sony KV-21FX30E
PostPosted: Tue Sep 15, 2020 2:26 pm 



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Taiyaki wrote:
If so I have yet to see a single CRT that doesn't do that on some part of the picture. It's usually not something that any setting (yoke or otherwise) can alter.


You actually can alleviate bad horizontal linearity by altering one specific capacitor in the horizontal deflection circuit.

Here's a link to some literature:
https://patents.google.com/patent/EP0844786A1/en

In German it's called the Tangenskondensator, Google says it's called the "S-shaping capacitor" in English.


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 Post subject: Re: Fixing black crush on Sony KV-21FX30E
PostPosted: Tue Sep 15, 2020 3:10 pm 



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SuperSpongo wrote:
Taiyaki wrote:
If so I have yet to see a single CRT that doesn't do that on some part of the picture. It's usually not something that any setting (yoke or otherwise) can alter.


You actually can alleviate bad horizontal linearity by altering one specific capacitor in the horizontal deflection circuit.

Here's a link to some literature:
https://patents.google.com/patent/EP0844786A1/en

In German it's called the Tangenskondensator, Google says it's called the "S-shaping capacitor" in English.


That looks fascinating, thanks for sharing. Are you sure we're describing the exact same issue though? Because I remember the BVM had an S shape correction setting ifI remember correctly and that didn't fix it. The issue I describe can usually be seen even when the sets are off. If you use a strong light and move a object infront of the crt and you will see it distort in the reflection in the same spots where it distorts while in use (not visible on all, but on some tubes this works). I used to have two BVM's of the same model (20G1U), and they both had the exact same same flaw in the exact same spot, despite both having undergone radically different hours of use, and both being from different years. On some sets this distortions happen on the horizontal field on others vertical, sometimes both (if the effect is less pronounced that way this can sometimes be preferable).


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 Post subject: Re: Fixing black crush on Sony KV-21FX30E
PostPosted: Tue Sep 15, 2020 4:02 pm 


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Taiyaki wrote:
You refer to the distortion that looks like the picture scrolls over a pencil (stretching in and back out)? If so I have yet to see a single CRT that doesn't do that on some part of the picture. It's usually not something that any setting (yoke or otherwise) can alter. I have no idea what the exact term is, but I had it on both BVM monitors too, and every PVM I've seen too). My best consumer crt's have it in much less pronounced ways but in more sections of the screen but in smaller degrees, so things feel more evened out if that makes sense (vs having one terribly noticeable warping spot).


Yes, exactly that. Horizontally scrolling game look near perfect, but in vertical shmups etc. it's quite noticeable at the top. All TVs seem to have these two adjustments

Image

so I figure I can make it at least a bit better. Haven't gotten around to trying yet, mostly been busy playing SMS/Famicom/OGXB on my new screen :-)

Taiyaki wrote:
Yes bigger screens tend to have both worse geometry and convergence. The middle sized tv's at 20 and 24 inches seem to be the cutoff point where these two get worse very fast for each size up, at least that's my experience, but I lost interest in 27 inch and up tv's a long time ago now.


Yep, 21" is very comfortable and easy to carry around, 25" is borderline. I'd love to find a great condition late 90s 25" Sony with this type of case:

Image

The 25" with this design are about as large as most 21" screens because of the slim bezels, no giant speaker grills etc.

Taiyaki wrote:
Convergence on the corners/edges is never expected to be good, usually it's red or blue that stands out. Some people manage to get good corners but generally at the expense of the geometry, it's usually an either or, or a compromise, whichever you find most agreeable. I tend to favor geometry myself as geometrical lines being thrown off at corners or edges draw my eyes more to it than some convergence color issues would.


Agree, geometry > convergence. I mostly notice on 240p content that the scanlines look uneven when convergence is bad.

SuperSpongo wrote:
You actually can alleviate bad horizontal linearity by altering one specific capacitor in the horizontal deflection circuit.

Here's a link to some literature:
https://patents.google.com/patent/EP0844786A1/en

In German it's called the Tangenskondensator, Google says it's called the "S-shaping capacitor" in English.


The Germans have a word for everything! Interesting. I always think CRTs could've gotten so much better with modern digital control over everything, like how digital control made the flat screens possible.


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 Post subject: Re: Fixing black crush on Sony KV-21FX30E
PostPosted: Wed Sep 16, 2020 12:57 am 


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25'' screen is about the ideal size as far as I'm concerned, for a non-desktop convenient setup.

Lo-res graphics look great on 'em, they're big enough to place 6-to-8 feet away and game from a good chair/couch, and they don't weight nearly as much as the 32'' sets (about half the weight actually) and a good 30 lbs less than the 27-to-29 sets usually.
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 Post subject: Re: Fixing black crush on Sony KV-21FX30E
PostPosted: Wed Sep 16, 2020 5:10 am 


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FinalBaton wrote:
25'' screen is about the ideal size as far as I'm concerned, for a non-desktop convenient setup.

Lo-res graphics look great on 'em, they're big enough to place 6-to-8 feet away and game from a good chair/couch, and they don't weight nearly as much as the 32'' sets (about half the weight actually) and a good 30 lbs less than the 27-to-29 sets usually.


Also the hardest to find, here in the USA (in my area at least.) :(


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 Post subject: Re: Fixing black crush on Sony KV-21FX30E
PostPosted: Wed Sep 16, 2020 8:05 am 



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Taiyaki wrote:
Are you sure we're describing the exact same issue though?


Yeah, my bad! I seem to have misunderstood you as ASDR also said he's referring to vertical scrolling (we are on the shmups boards after all :oops: :lol: ).


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 Post subject: Re: Fixing black crush on Sony KV-21FX30E
PostPosted: Wed Sep 16, 2020 12:10 pm 


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SuperSpongo wrote:
Taiyaki wrote:
Are you sure we're describing the exact same issue though?


Yeah, my bad! I seem to have misunderstood you as ASDR also said he's referring to vertical scrolling (we are on the shmups boards after all :oops: :lol: ).


This is probably further complicated by vertically scrolling TATE games where you'd need good geometry for horizontal since the monitor is rotated :D


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 Post subject: Re: Fixing black crush on Sony KV-21FX30E
PostPosted: Wed Sep 16, 2020 1:07 pm 



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GrimShins wrote:
Sub-contrast and sub-brightness are used to set the value of the Contrast/Picture/White Level and the Brightness/Black Level when the user adjustable picture controls are set to the middle of their range. This ensures that there's an adequate amount of adjustment room in either direction to correct sub-optimal signals. Unless you've already got the user controls set to min/max, adjusting the sub- controls in the service menu won't yield better performance.

Additionally, CRTs in production environments weren't adjusted for the deepest blacks possible; the black level was set with a PLUGE to ensure that no shadow detail was visibly crushed. When the PLUGE is set correctly, there's a good chance that the black level will be elevated from the absolute minimum luminance the display is capable of.

According to the seller, my PVM-20M4E came straight from a TV production house (in what looks like great condition to me) and sub-brightness was set right where 1 IRE is just about visible on a PLUGE pattern, albeit on a bed of dark grey when playing in a dark room.

FWIW, all CRTs I've used are like this. The formulations specified in BT.1886 to accurately match a CRT will also crush shadow detail at a low black level.


Last edited by ross on Wed Sep 16, 2020 1:10 pm, edited 1 time in total.

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