Death by Poking

On the subject of early 'fragile' monitors, kill-able by the wrong refresh rate: I was always under the impression that, being by neccessity rather cheaply engineered and produced devices... the designers used many of the long-standing "tricks" from decades of consumer TV practice to "get by with less". Anyone who has worked at all with (especially 60s-era) TV sets will know what this means. The beam deflection circuits in most monitors have magnetic deflection coils around the neck of the CRT (called the deflection 'yoke) which carry the vertical and horizontal sweep frequencies and thereby move the internal electron beam around on the face of the CRT screen. Since the early monitors were designed to run at very limited sweep rates (or even at one single sweep or refresh rate) the engineers could use a factor called "resonance" to get by with less wire in the coils and simpler electronics to drive them Basically, the yoke coil is calculated to 'ring' at a certain frequency, and of course this is the horizontal refresh rate. The circuit is designed so that at that freq, the yoke is in resonance, and therefore uses less current to get the job done; hence less wire and lighter, cheaper parts. The circuit is made to be resonant over just a narrow range of frequencies (called the 'Q' of the circuit) and if the driving signal strays very far resonance, it begins to draw large amounts of power trying to do the same work, and, in a lot of the 'cheap' monitors, the whole thing actually overheats and burns up while you are looking at the jagged lines and trying to figure out what to do next. Any kind of setting (hardware or software) which could alter the horizontal rate without reagrd to the type of CRT device it's driving is liable to this kind of smoke-producing behavior. Newer multi-sync CRTS have spoiled us... ALSO: Long ago in the Big Iron days... the were some machines in the Philco line whose power supplies in some configs were marginally inadequate. It was possible to load the machine (with programs and data) and trip (or burn) the power units... but this was an isolated case. Program damage to most older computer systems was mostly caused by making peripherals do things they shouldn't... usually in cases of the device handler software being abused or tweaked by The Unwary and causing resultant mechanical damage. Cheerz John