Dot Test Pattern on my Trinitron CRTs

[sonypete]

Hello,
Guys I had a quick question since picking up my recent PVM-1954Q monitor. It's something I've noticed on a couple previous Trinitrons I had. When viewing the DOT test pattern to ensure circular dots are generated, the farther out to the sides you get the less round they are. The dots in center portion are great but farther out you go the wider they get. look similar to the sun on the horizon.

Thing is, this is how my previous CRTs looked as well. So I'm beginning to think its just a thing all CRTS have to an extent due to the technology. Or am I off base and there is a method to calibrate this. If so what can fix this potential anamoly?

- Pete

[niall]

I'm not familiar with the PVMs, but you need to adjust convergence. Traditionally on consumer tubes this means opening the chassis and adjusting the convergence rings (4/6 pole magnets sitting around the neck behind the yoke), but hopefully you have a digital Service Menu and can avoid all this?

It's not for the uneducated and uninformed - you're talking about exposing yourself to very high voltages here - the tube is essentially a capacitor holding thousands of volts, and it can kill. If you don't have a menu option, read up about this topic - research and research until you truly understand what is involved, and the risks, or perhaps contact a local CRT calibrator to do it for you?

It's infuriating though isn't it - my KV-2900 has great convergence but towards all edges it's quite noticeably off - then there's the purity quirks that I still need to address, either re-seating the yoke (it's slightly off horizontal anyway) or try to get some magnets onto the back of the tube underneath these damn Sony shields!

[sonypete]

Niall,
I associate convergence issues with seeing the Red,Green,Blue beams getting separated. This isn't the case with the dot test pattern.The dots are still white there just not uniformly round the closer you get to the edges. They get wider and lose height.

- Pete

[Taiyaki]

I believe what you need to adjust is the pin cushion or trap but I'm not really pro enough to explain the differences.

With my old crt I had problems where geometry looked very good on inanimate scenes, but when moving in a 2d platformer I could see the backgrounds expand before leaving the screen on the sides.

I believe a PVM must be able to fix such issues, a good guide for calibrating geometry would be very useful unfortunately I don't know of any.

[sonypete]

Taiyaki,
The grid patterns are actually spot on, excluding a bit of pin adjustment needed at the very bottom left and right corners. I know what your describing part of the reason I trashed a Samsung flat screen CRT as there was not adjusting the compressed sides out. Sonic was the worst to watch when playing as the sides undulated.

Niall,
I spoke to soon, I looke da bit closer and I do see a bit of color red and blue color bleeding on the left and right edges of the dots which are assiting to make them appear wider. It's really not noticeable at all in the grid patterns so I may just overlook it. I checked the Service Menu and doesn't look like their are any convergence adjustments.

If I do choose to torture myself I might be forced to pull the cover off. If recall correctly the manual controls on the PVMS are pretty straightforward. I really need to get my hands on a service manual. Unable to find one on the intranetz.

- Pete

[sonypete]

Looks like the TLH correction might do the trick from what I've read on other service manuals. I don't have the service manual for the 1954q specifically so hopefully the circuit boards have printouts on them so TLH is easy to spot. *fingers crossed*

- Pete

[22point8]

PVM 1454QM service manual http://1drv.ms/1l8F33a

My video review of it, has geometry instructions http://www.youtube.com/playlist?list=PL ... zfpehUepCv

[sonypete]

22point8,
I'm good on geometry like I stated earlier. I think the issue is the horizontal convergence on the left and ride sides. Which apparently is tweaked by either a TLH adjustment knob or a TLH plate on the tube.

The service manual you linked is 1454QM monitor. Does my 1954Q and your 1454QM share the same platform (i.e. pcb boards and adjustment locations)?

- Pete

[22point8]

The only difference should be the size, there are hardly any boards inside so they should be almost identical. The manual suggests that they are all the same and all that determines whether its a 1454/1954/2054 is a number in the service manual, obviously something like a 1450 has less buttons and is therefore physically and functionally different.

[sonypete]

22point8,
Thats good news then. I might just pull the cover off tonight and poke around ......zzzZAPPPPPPppppp!!! (I kid I kid)

- Pete

[sonypete]

Okay did a bit more reading before adjusting anything under the hood. I just wanted to run this past you guys first.

From what I understand I need to tilt the yoke up or down to fix the convergence on the left and right hand side of the screen. The areas where the dots become distorted and wider then at the center of the screen.

On my pvm there is only one wedge controlling the up and down movement and it located at the top of the yoke. I'm thinking I can just remove that and adjust and then re-insert and possibly use a hot glue gun to fix it in place.

What are your thoughts guys?

- Pete

[niall]

Can you post a few up-close shots?

Is it on all edges, or more towards corners, or only some edges?

Could be a combination of horizontal amplitude, pincushion, convergence and possibly linear convergence?

Re-seating the yoke is more for addressing rotation (horizontal lines disappearing more at one corner/edge than another) and purity (seeing strange colours at corners or edges when viewing 100% Red, blue or Green. Plus it's a pain in the arse to do, and get right - if this is your first chassis you're opening I wouldn't attempt anything as risky as this for your first pass at calibrating.

Post pics and try to describe horizontal or vertical lengthening or compression and where abouts over the whole screen, it may be a combination of 2 or 3 simple adjustments.

[cools]

Get us a photo.

[sonypete]

I'll see if I can get a picture asap.

But as I described before, the farther from the center you get the wider the dots gets. So its not on the edge but rather the progressive from dead center to edge. Dead center being perfect and the dots on the edge being widest. It's due to the red and blue guns shooting wider and wider the farther from the center you get.

I'm definitely new to the physical calibration side of things via the yoke calibration. But I definitely know what a some minor geometry adjustments can and won't fix

- Pete

[sonypete]

Okay guys here is an image. I apologize for the quality but it should be pretty clear how the dots are no longer uniform the farther from the center you get. What the picture does not show vbery well is how the dots get wider then the dots in the center. In this picture they seem to be of the same width when in in person they are not.

- Pete

[cools]

What you're describing is the reverse of side compression which is a common trait of CRTs. As long as the yoke is firmly in place you should assume it was fitted there from factory where it would've been installed to its best capability, so moving it is unlikely to improve anything unless it's been shifting since then - and what you're describing doesn't sound like anything that would happen with a mispositioned yoke (I've performed yoke swaps and you get "projection" errors and colour problems, but not linearity issues)

EDIT: Looks like focus to me.

[sonypete]

Cools,
So based on the image I just uploaded you think it the focus adju stment that might reduce this dot uniformity issue?

- Pete

[cools]

Yes, although I'd be surprised if you can fix it if the tube is single (rather than dual) focus type.

Focus is/are a(n) easy pot(s) to play with to try and improve things. Tough to do wrong.

[sonypete]

Cools,
I'll mess around with the focus pot. I was under the asumption focus was mainly used to adjust the center of the screen and not much use towards the outside of the screen.

- Pete

[cools]

You're supposed to adjust it to get the best possible picture in the centre, correct. However you may find that adjusting it slightly has no detrimental effect on the centre but a dramatic affect on the outsides - it affects both areas.

[sonypete]

Cools,
Ahh so sacrifice a bit on center (almost unnoticable) for corrections at the end.

I do have a second adjustment pot underneath the focus pot (On the FBT body) but it's unnamed and has no effect on the screen when rotating it. Nopt sure what it is or how to utilize it. Your thoughts?

- Pete

[niall]

Yep focus might help somewhat, I'd also consider tweaking convergence in the same way - optimise for the centre of the screen but if you can take it a bit further, improving the edges and corners without going too far and putting the centre off further than you'd like .. repeat as necessary.

In the end a consumer CRT isn't going to give you perfect geometry and convergence, but do as much as you can with whatever pots you have available, before attempting anything more complex like alloy strips and magnets glued to the back of the tube around the yoke.

What pots do you have - any chance of photos of those with any writing around them (could be on front or back of board near component) or have you managed to find a service manual for your set?

My Trinitron has a fair bit of convergence and geometry issues at all edges, and purity issues in 1 corner - the only thing that's going to help with that now (after I've tweaked all pots as best I can, from behind the set with a mirror is really quite difficult to get right) is for me to start gluing alloy strips or magnets into place on the back of the tube around the yoke - a bit further out for the edges and corners. To be honest I'd rather re-locate all of the pots from inside to the front of the set first, so I can dial in those while sitting in front of the screen. Then a final purity/convergence pass, then I'll look at cleaning any final bits up with rare earths glues to the back of the glass tube. And it will still be far from perfect, but for a consumer grade TV that's about as good as you'll get, and I'm happy with that. Calibrating itself is fun, and I find it rewarding, but YMMV

Safety: don't touch the flyback or red cable, don't even get near it, and always keep 1 hand behind your back to avoid a current through your heart if you do get zapped - but you still may die, just be damn careful and read until you're full-bottle and understand what you are doing and the risk of doing that. You're literally taking your life into your own hands here, I would only do it with someone else in the room who can push you away if you do get shocked (with rubber soled shoes or a non-conducting broomstick or something) and who can call for an Ambulance etc. Never work alone, and always know what you are doing (and the risks involved) before you do it - plan and walk it through mentally before you do it.

[cools]

Second pot will be screen volts and doesn't need adjusting normally

[sonypete]

Niall
The below Model and Service Manual basically matches my insides spot on. If you can spot anything I might be overlooking I'm open for suggestions. Tweaking focus did not help the side unless I went really blurry and then all dots were simliar in shape but really just an unwatchable picture overall.

PVM 1454QM service manual http://1drv.ms/1l8F33a

- Pete

[Taiyaki]

What exactly do you guys mean by focus? I've never seen that setting, is it related to the sharpness?