Purity issues on a HP MX70 Monitor
 

I got pretty lucky getting this unit from Ebay; they seem to be pretty rare in the U.K.

Works perfectly fine apart from the fact that I have all colours at 90/100 and there seems to be some orange/red tint in most of the screen. However, what irks me the most is that it seems to be more exaggerated on the right hand side of the screen. I've used the built-in degausser a billion times to no avail and I've turned down the red using the monitor's OSD to 70, leaving the other colours at 90 which actually seems to help but obviously is kind of a brute force 'fix'.

The issue seems to present itself most noticeably when displaying whites and greys.

I struggle to get photographs because my phone craps itself when it sees a pure white screen, but if needed I can try if anybody needs it for diagnosis. I honestly just want to know what the issue is and if there's a non-invasive fix that won't end up with me frying my nervous system. If not, I'd just be happy to get closure on what I'm dealing with and live with it.

Cheers!

First you need to diagnose what the problem actually is.
Can you put up a pure red screen (and then blue and then green) to see if there is actually a purity problem (or if it's something else)?

First confirm the built in DGS is working. Measure AC amps at COLD
start. Should swing up to 2 amps +- then drop to apx .75 amps. Analogue meter
is best for this. If it dont look for cold joints on PS module.
Next be sure no yoke shims or little correction magnets have fallen off.
Also look at the CRT neck magnets. Usually after set-up they paint white
stuff on them to hold them. Look for evidence they moved.

Thats the general idea. BTW Purity is done with only one color operating.
Usually green on in-line jugs.

best 73 from the colonies !
Zeno:smoke:
LFOD !

My bad, this is the kind of stuff that is way beyond my skill level. I've always been told to leave the insides of CRTs to experts, unless I want to kill myself :P

The only real option for somebody like me is to describe the issues I'm facing and essentially eyeball it.

Hmmm, red, green, blue, all looks fine to me. It seems to be a case of if there's greys or whites on one side of the screen they're kind of overlayed by this orange hue. It's really difficult to pick up on my phone, perhaps I'll need to ask my friend to use his.

I've messed with the horizontal and vertical size & positions and it seems to simply move where this hue is. I don't know much, but I had put it near a window for a while as I needed to make adjustments to my desk to accomodate it :P I thought maybe the sunlight had messed up the phosphors but I think this confirms it is something else.

Sunlight would not mess up the phosphors. A picture would definitely help.

My friend has a much better phone, and I think it did a good job of illustrating the problem. If you look on the right side of the screen closely, you can see a sort of orange crescent which is most exaggerated in the bottom right.

It's a lot more annoying in real life, especially when you're surfing web pages and one part of a text box is orange and the other part is white or grey...

Extremely hard to see in the posted image. I had to open it in Irfanview and increase the contrast to max to see anything.
White field impurity problems were essentially eliminated in the mid 1960s with the introduction of negative guardband tubes. I wonder if there's a phosphor saturation problem due to sharp focus varying over the image. Is there a focus adjustment you can try to see if it affects the problem?

Is it reduced by turning down the contrast/brightness?

If you have a dark image for a while and then put up the white image, does it gradually get worse?

Seems to be there all the time, but yes it seems to 'warm up' to my eyes i.e., gets gradually worse until stabilising

This could be shadow mask "doming" (expanding) with temperature. See if it reverses if you turn the brightness/contrast down for a while.

It didn't seem to do much, but I'm being a bit impatient so I'll do some proper testing tomorrow.

You probably know what you're talking about, so I'll assume it is indeed 'doming'. Every example of impurity caused by magnets I've seen online seems to have a much more apparent and catastrophic result than the subtle but noticeable enough to be frustrating issue I'm having. I'm beginning to get used to it though, I think(???) :P

On another note, it is connected to an HDMI to VGA connector, but common sense would tell even me that this has nothing to do with it, could be wrong though?

Thanks for bearing with a newbie like myself, I'm quite new to the world of CRTs!

This could not cause it. A problem with the connector would not be subtle.

Is too large the colored areas, or is only near the contours/lines? (to be sure)
Some not so focused CRT can exacerbate convergence issues. Especially on high resolutions, one can not expect a "LCD" pixel resolution, although some hi-end monitors are very good with this.