Sony PVM bowing issue.

[Drojman]

Hi folks,

I picked up a new CRT recently, its a PVM 20M2MDE. I am really enjoying the thing, but cannot for the life of me quite get the geometry right. There's bowing in the upper cornersr of the monitor, I've heard it can be due to convergence strips, or magnets need adjusting etc, but I'm hesistant to touch anything. I've tried the pin controls, but they don't seem to help, I can straighten the image, but no matter what the corners bow outward.

Here's a picture which kinda illustrates what I mean:

********************a/N8u7smS

Was wondering if you might have any idea as to what might be up?

Thanks

[red16v]

Yes, quite a few of the Sony professional range of monitors use magnets stuck to side of the crt to correct for various geometry deficiencies. Strip magnets thrust down the throat of the scanning coil held in permanent place by double sided tape integral to the strip magnet itself and, round button shaped magnets also stuck with double sided tape in the vicinity of the corners of the crt to correct for smaller imperfections in corner geometry and corner convergence. To be honest you can only do this with any degree of certainty with the monitor powered up and displaying a cross hatch raster as shown in your photo.

I’ve performed this routine on many Sony monitors. When I was at work I used to keep a stock of these magnets in my tool box - mostly stripped from scrap crts. In taking them off from scrap crts the double sided tape almost always tore apart or remained on the donor crt. So, I used to have to adjust the magnets to get the correct geometry result, try and keep the magnet in place with ordinary sellotape, then seal it in place with a blob of silicon and leave it to go off overnight. Quite an intricate proceedure, and do remember the monitor has to be powered up to the actually see the results of the adjustments - insulating gloves were definitely the order of the day.

Looking at your image, to be honest I don’t think you’ll get it much better. I would leave well alone given the potential for heartbreak or worse. There are high voltages inside these sets - beware.

[Vintage Engr]

I'd go along with that, it's probably as good as you'll get it.
I must have done hundreds set-up on all grades of Sony monitors, & unless it's a Grade 1 broadcast monitor, the edge geometry can vary quite a lot.

Dave.

[Drojman]

Thanks for your advice folks. I am tempted to leave it as is, and I'm not convinced I'd ever notice it in game/during any film etc.

I may take a quick peek at the convergence strips, but not even sure I'll do that.

Thanks.

[Refugee]

I think they are preview monitors for satellite links hence the PVM model numbers.
An upgrade to wide screen got me s couple of them for free saving the previous owner the disposal cost. They are more than good enough for DVDs.

[Drojman]

Depending on what one you have they're fantastic for older games too!

I had a fiddle with the convergence strips. It's possible a slight improvement, but not perfect. I wonder if a recap would help. For now I'm just going to slightly overscan the image and not worry about it.

[simpsons]

Whilst I haven't come across strip magnets, I recognise the corner convergence correction strips Sony Part X-4387-214-1 which are described as permalloy.

When using them, the geometry of the picture can also be affected and this is where very small bar magnets can be used to compensate their effect. Placed at the rim of the scanning coil, close to the neck of the tube, they will alter the corner geometry but first check that you are unable to correct the shape through the service menu.

The magnets I use are not SONY parts but from scrapped TV scanning coils which have them fitted within the scanning coil to correct pin cusion distortion and approximately 10mm X 3mm. The larger the magnet the greater it alters the geometry.

Looking at other threads on Trinitron displays, the problem of getting it perfect is often down to the CRT and compromise but with care and patience you can be as near as dammit.

[Heatercathodeshort]

Originally Posted by Drojman

I wonder if a recap would help.

Don't even think about it. John.

[Lloyd 1985]

Probably best to leave well alone! If you start messing with the convergence it can quickly end up ten times worse! Guess how I know that....

I have one of the little 9” PVM monitors (the plastic cased version) lovely little thing, picture is fantastic! Playing the output of my HD camcorder through it (in SD of course...) it was nice and clear with excellent colours. Shame it wasn’t the fine pitch phosphor version!

Regards
Lloyd

[Drojman]

Thanks all, going to leave it as is for now. I might buy some proper double sided tape to make sure the strips stay where they should be but other than that I'm going to leave well enough alone!

Oddly enough I've found that in the monitors underscan setting, I can get the lines straight, so there must be something in the OSD to adjust it, but it's certainly not the pinamp settings,

To be honest I'm not going to worry. The 240p test suite I've been using is pretty much designed to highlight imperfections. In actual usage I don't think I'd spot a thing.

[Maarten]

Since the bow is displayed in red in your picture, it's impossible to know for sure whether it's a convergence or a geometry issue. Only a convergence issue would be adjustable using permalloy strips or magnets in some cases. Since the fault looks symmetric, I rather suspect it should be adjustable electronically (E/W correction, though Sony has other names for that) or it's a defect that could be repaired.

Edit: I didn't read your last message yet. It is definitely something electronical then, probably an adjustment.