konc wrote:It is, that and many more. It's not a terrible monitor though one that doesn't work way out of specs.
The same will happen to monitors appearing to be working or loosing sync, if you keep them running like this long enough.
I have my doubts, but I don't seem to have any such monitors, and I'm not about to spend a few hundred to get one if they're actually as bad as this - I'll just take your word for it.
maxtherabbit wrote:Yep. "Sync" on the 5150 is actually a misnomer, since the HV pulses actually drive the deflection directly
The 5150 does not generate anything near high enough voltage to drive deflection electronics directly - It doesn't position the beam either. I'm 100% certain that it does not - It's bitmap, not vector.
Scali wrote:TVs, by their nature, generally do not work that way.
They have their own oscillation circuit, which is synchronized to the inpu […]
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TVs, by their nature, generally do not work that way.
They have their own oscillation circuit, which is synchronized to the input signal, within reasonable parameters.
Otherwise any TV would blow up as soon as you turn it on without it being tuned to a proper channel (or just forgetting to plug the antenna in).
So if a TV doesn't get a proper sync signal, it will just be 'slightly' out of sync, and still within reasonable parameters, so nothing gets damaged.
Since many early colour monitors are based on TV technology, they also have this circuitry in place. Some MDA monitors also have it (I know my Philips one does, but then again, Philips was one of the largest CRT/TV manufacturers back in the day), but generally MDA monitors were just made to be as cheap as possible, like the 5151.
So rule of thumb is that colour monitors are safe, but MDA monitors are not.
Well first of all, I didn't say anything about television. This is about computer monitors.
A television with an improper input will just end up with a rolling picture or losing color, all number of other minor symptoms. It won't be damaged by it because there's nothing to damage.
Kinda sucks they would be that cheap - I can't imagine it would save much, if any money to exclude what in most televisions and monitors is driven by a subsection of a single chip at that point. They already have to have translation electronics to actually receive the TTL signals, it can't have cost but a fraction of a few pennies to just attach the connection.
If an MDA monitor truly is direct drive, then I still have difficulty seeing how one might be damaged by improper synchronization, since many CRT oscilloscopes have no problem receiving any signal in X-Y mode, which disables the oscillator inputs entirely. If the 5151 and other monochrome monitors truly have no oscillator, they should be able to sync to just about any signal you feed them. If they're being directly driven by the video electronics, there is no reason it can't just... Feed it different signals.
I.E. Unless the monitor is generating SOME signal of it's own, it can take any signal as timings for the scanning speed.
There have to be sweep electronics internally, since the MDA/Hercules boards do not generate that on their own. The monitor is almost certainly always sweeping at a fixed speed a fixed amount of time after the horizontal pulse, and there is likely at least a basic counter or sweep electronics to drive it vertically.
Many of the signals needed to produce a valid picture are not included on an MDA card, so there has to be some oscillator inside the monitor, otherwise it's a glorified oscilloscope stuck in X-Y mode.