MiSTer FPGA Forum

I haven't found an answer to this question. Can (false) custom video mode settings harm a CRT in short or long-term?

Like so many other things (relative necessity of fan, inline switches, etc.), people will argue this point. I can feel it coming.

The unfortunate answer is : if the device wasn't designed for those settings, there isn't enough information to make a statement.

But if it works, then it's fine... until it isn't fine anymore.

In other words, you take your chances - and whether those are favorable (not much chance of harm), or unfavorable (chance of harm), you will be the underwriter of that risk, so it pays to learn as much on the subject as can - specific to your own circumstances (ie. manufacturer, model, original specs, custom specs, etc.)

Ah, but there's a lot less arguing involved on this point!

Yes, you can, for sure damage a CRT if you attempt to drive it beyond it's known operating ranges. I know first-hand this to be the case as I've seen many CRTs go pop in my time

The main thing here is that there's an electron beam whizzing around inside a vacuum tube and it can only go so far, so fast. Try to drive it outside of those ranges and the protection circuitry in the device will only do so much before something gives up and doesn't protect any more or something gets too hot and dies.

The nice thing about it though (if you can call it that) is that you usually know when you're pushing things too far because you usually hear the thing squeal before it goes pop / bang / shuts down.

[EDIT] Of course the more "modern" the CRT, the more likely it is to have detection circuitry that will know you're trying to be daft and just tell you it's not going to do what you're asking it to do. It's far from a given on any old CRT of that being the case though.

I burned some spots into a CRT by shortening sync lengths, simply with the settings in Windows, trying to get the clearest possible picture (the irony).

The display collapsed horizontally, then vertically, turned off, wouldn't turn on again until I pulled the mains plug and plugged it back in.

Then there was a vertical row of large burned-in spots.

A real shame, as the display was only a few months old. Luckily I got it for free as a nearby office had tossed it because the power switch didn't work well, which was an easy fix.

EDIT: That was a modern multi-sync CRT BTW, somewhere in the early 2000s.

I once blew up a very expensive 19" CRT monitor in a spectacular, blinding flash. I'd compiled my own Linux kernel in a bid to get an old 28" CRT TV working as a dial screen output from a crappy composite out. I'm guessing I messed up the screen output settings. Thankfully the crappy old TV output actually worked fine though - haha.

But yeah, you can kill or damage a CRT with the wrong settings.

Yep, as stated above.. CRT's can and will fry when pushed with the wrong signals. Many newer ones have detection in place and will simply show a message like 'input out of range' or similar. Others will go wonky for a bit, and still others die with a pop.

In my case the protection system that was there sadly wasn't fast enough.