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FrostyBrows's picture
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Joined: 2020 Feb 14
USB Display Service Utility (USB DSU)

I recently picked up a CRT 21" Apple Studio Display monitor in great condition but I desperately need this software to help me adjust the settings (Specifically High Voltage settings), USB Display Service Utility for MacOS.
Here is some information I found on this software:

https://www.macrepaircentral.us/studio-display-21-crt/usb-display-servic...

If anyone can dig this up for me from their older setups that would be amazing, I'll even send you a donation via paypal for your efforts...

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OpenSourceMac's picture
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Joined: 2019 Jan 21

What's the monitor doing? I've worked on a number of these and it doesn't usually require anything special. I presume the monitor is dark - is that right? If so, on many monitors, there are two plastic adjustment screws on the side of the flyback transformer (where the thick cable that goes to the side of the CRT comes from). High Voltage and Focus. As CRTs age and go dark you can often give them a brightness boost by turning up the High Voltage, but often just a LITTLE change will work miracles. You can often buy back 2-3 years on the first adjustment. BUT there will be a noticeable lack of color range. Often a dampening of the reds, and a few other pure colors.
So you might want to start with a Gratag/MacBeth or other color-chart and slowly turn up HV and try to find the sweet-spot where you get a balance of acceptable brightness is and the color range remains as broad as possible. Then you finish off by just checking focus with something onscreen with detail like text. You can't make the tube new again, but you can make it totally usable - especially for non-color-critical work.

How well it works often goes back to the cause. If the screen is 'gassy' and has leaked in a bit of air, you are much more limited in how far you can push it, but if it's just old, and has not yet began color-shifting, you might get lucky.

**NOTE - of course be careful around high-voltage. I've been shocked a number of times, but it is usually pretty low amperage, but for people with a weak heart you still want to take procautions.

FrostyBrows's picture
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Joined: 2020 Feb 14

Oh joy, you've already given me some hope. Yes, the issue is simply that the screen is a tad dark for my uses - I imagine it really just needs a nudge. Now this thing is pretty massive and as I have very little space I'd rather not try to dismantle the thing.. I found a service manual for this display and it keeps saying to use the USB DSU (Display Service Utility) program to make adjustments (see link). I managed to find an older DSU program but it lacks the High Voltage setting that is only in the USB DSU..

https://www.applerepairmanuals.com/the_manuals_are_in_here/Studio_Displa...

I have noticed the there is slight color shift near the corners of the screen too, what does this mean? When I go to adjust the convergence I can't seem to get it right across the whole screen so I get the center aligned and that's about it. It's not a huge issue, just more noticeable using lower resolutions..

Anyway I can live with the slight color shift but I really need that elusive USB DSU...

OpenSourceMac's picture
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Joined: 2019 Jan 21

Good luck finding it. The color-purity issue you mention is likely do to some magnetic absorption from the shadow mask on the edges from being too near a speaker. Degaussing is usually what fixes this. You can get one pretty cheap on eBay like this one: https://www.ebay.com/itm/WalscoElectronics-Model-2592-Degaussing-Coil-Us...

If for what ever reason you don't find that program, I can assure you this is one of the easiest repairs there is. You might just need to remove the rear shell to access the flyback. Then since you have to adjust while it's running, just make sure to use non-conductive screwdrivers.