AT&T 6300 mono monitor

On 12/27/2012 03:25 PM, Chris Tofu wrote: Well, that's the problem with the 5151. Somewhere back in this discussion I mentioned that it didn't have the standard oscillator-with-synchronizer setup. And indeed the 5151 has no horizontal hold control. The horizontal sync signal directly feeds the base of the horizontal amplifier, TR22, which then drives the horizontal output TR23 through transformer T501, which then drives the flyback transformer T502. No oscillator whatever. There are width and linearity coils in series with the horizontal deflection coil, but that's it. And that's the huge weakness in the 5151--rather than drop horizontal sync and go into a roll, it'll stay synchronized to whatever horizontal sync pulse that's given to it, even if it means blowing out the FBT, which happened more often than IBM let onto on the 5151. ...which is what I've been trying to get at all along. The 5151 is too stupid to just lose sync if the horizontal frequency is out of range. It does have a vertical oscillator (in IC401) but nothing in the horizontal. I don't have a copy of the schematic for the Egale PC (or even the Eagle 1600 for that matter), but I suspect that, to keep costs down, it was just as brain-dead. --Chuck