I should ask, Zebidee, have you ever had a problem with a PVM-2730 where the colours smear or bleed to the right, particularly red? And it gets worse as you turn the brightness up? - https://www.aussiearcade.com/showthread.php/81404-The-PVM-2730QM-thread-(H-STAT-issue-colour-bleed-convergence-and-more!)?p=1202708#post1202708
Buttersoft, I've yet to finish reading through that 11-page thread on AA in detail, but I can tell you now that I've definitely had that problem (and only partly solved it). Apologies for a long-ish post, I try to include all relevant details without warbling on too much.
I noticed this problem with my Sony PVM sometime last year, and it seemed to happen quickly/suddenly. I'm not sure what caused it, maybe old age (the Sony, not me!) or maybe when my wife got 4 guys to move/manhandle the cab while I was in the shower one day (despite my warnings for her to never move it without me). When I found out, I asked her "
Four guys! Why? I can move it by myself. You know my cab has wheels on the back, because I've told you about 10 times, yes?". To which she responded "
Oh! It has wheels! How convenient, if only we knew...". Cab survived an oceanic voyage between hemispheres but is undone from being manhandled a few metres. Hurrrrrr......, anyway, the cab I'm talking about, which has the Sony PVM2730QM in it, is the second last on my sig line below.
Whatever the cause, I found the same problem you have: that the red was bleeding a lot at brightness levels that are "normal" for everything else. Turning brightness down reduces/eliminates the red bleed, but then the image is too dim.
Using some monitor test images, I discovered was that "vertical" convergence was way out ("vertical" convergence = vertical
B|G|R| lines coming together =>
||| =>
|). In particular, red lines were shifted to the right, especially towards the right side of the screen, although there were some other issues there as well (sorry no pic). You need to get a good test image/grid pattern on screen to see how much. I used the Nokia test (Ntest) software (but that is 32 bit, doesn't work on x64 CPUs, so find/use something else for 64 bit OS).
I tried adjusting the "dynamic" convergence (the panel of pots at the back/left) and this helped, but was insufficient. They are only for fine-tuning. The best I could get, with various pots at max/min values, was just barely OK. Note that the "geometric" pots on the left side do nothing to help with convergence, they just control things like screen shape/pincushioning.
Adjusting the "H-stat" pot (which is actually for vertical convergence, despite the name), just a little bit, solved the worst of my vertical convergence problems. H-stat is located on a black box halfway between the neckboard and the anode cap. Further re-tweaking of the "dynamic" convergence pots improved things even more.
With vertical convergence fixed/improved, picture was much clearer, red was bleeding less but still bleeding too easily. This might be because the blue gun wears out faster than the red! Apparently this always happens over time in these Sony's, according to some Sony repair guru I talked to last decade. Using the Nokia test software, it as obvious to see that the blue was coming out weakest and the red strongest (sorry no pic available).
After adjusting gain & brightness, all that is left to adjust is the blue/red cutoffs (there is no green cutoff, as that is the baseline). Unfortunately those pots are on the inside of the neckboard, which is almost impossible to access in my cab! I managed to twist my wrist somehow to adjust the blue cutoff and this improved things somewhat, but I can't get any more blue brightness that way. I can't seem to get to the red cutoff pot because of the way my cab is, there isn't much room in there.
STATUS: This is where I am now with the Sony. I can now adjust brightness so that there is no red bleeding, and most things look good, except for faint blues which just come out black (I don't mean "light blue" or "sky blue", as these actually have a lot of "white"). For example, the first stage of Time Pilot (with WWI biplanes) has a faint blue background and it now looks black on my Sony.
I can make Time Pilot etc look good/blue again by adjusting the gamma levels (ie using the slider controls in MAME), but obviously this is an imperfect work-around.
NOTE: I did these adjustments over about a week, as I don't like spending too much time fiddling at the back of my Sony. I've had some minor dizziness when spending too long there, which reminds me that I could be exposing myself to X-ray emissions! I've already had all the children I need, but don't want to push my luck.
If I can manage somehow to access the red cutoff then I should be able to choke the red levels back, closer to the blue levels, and thus eliminate the red bleed. Then I should be able to raise the gain/brightness a bit so that I can see faint blues better. To access the red cutoff I may need to temporarily remove a vent and fan from my cab. I've postponed that as I recently had hand surgery and, in any case, am in a different city than my cab atm - hopefully I'll get to it in a couple of weeks.
EPILOGUE: It seems that I had/have two issues going on, blue gun getting weaker and convergence. Because of the convergence issues I found, I half expect to find that one of the magnetic strips used to fine-tune CRT convergence has fallen off while the cab has been moved. I'm pretty sure of roughly where is must've fallen from too. I may try placing a mag strip there later to see if I can improve the convergence.