I just scored a Sony PVM 20m2u monitor the other day and found that the picture was extremely sharp at the edges but slightly soft toward the center, which indicates that it was a bit out of focus. There is no focus setting in the service menu (accessible by pressing the degauss and enter buttons on the front, btw), as it is a physical characteristic that must be adjusted by turning a pot inside the monitor guts, just like on an arcade monitor.
With most(?) arcade monitors, the focus pot is located on the flyback transformer, along with the screen pot that controls the voltage to the electron guns. If you remove the outside case of your PVM and look in from the left (there's a big circuit board thing blocking view from the right), you should see the flyback, which is the big black piece of plastic with wires coming out of it that lead to the neckboard:
There are no easily accessible pots to turn on this flyback, but it is connected to a small white board above and behind it, right against the back panel with all of the inputs (which I did not remove), and that board has our focus pot:
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| The focus pot, viewed from the back of the monitor |
You'll want to turn this pot very slightly while the monitor is running until you have a more uniform sharpness all over. It's nice that they moved it off of the flyback, actually, even though it made it a little harder to track down because it can be scary messing with such a high-voltage component while the monitor is running.
UPDATE (03/20/2015): Someone in the comments asked for shots of it running, so here you go (click thumbnails to embiggen):
These are all extreme closeups, since I figured that's what people are mostly interested in. These were taken with my HTC One m7 with a Playstation 2 hooked up over component cables. The first 2 are Dodonpachi Daioujou in TATE (notice the vertical scanlines), followed by a menu shot, Mega Man X Collection and Street Fighter Anniversary Edition.
As you can see, the scanlines are very crisp and "sterile," though not as much as on a 31 kHz CRT monitor (see the pics
at the bottom of this post for comparison). For "240p" non-interlaced content, the PVM sits somewhere between that extreme and a regular SD/CGA TV or monitor, where the gaps between scanlines are almost nonexistent in bright areas.
