W076/M452 replacement cards

Actually, DEC derives a +0.7V supply with a 150 ohm resistor and some diodes, then uses a transistor to close the switch between *that* and -15V through the teletype mod. This is the 150 ohm resistor only rated for 57ma. Moreover, *another* diode clamps the reader enable line to ground, so the actual voltage on the positive side of the reader run option is at most one diode drop above ground. I have no idea why the reader run circuit is run supposed to leave 15V for the reader run circuit. That, in turn, would imply that the reader run circuit won't run on, say, 14.3V, which is only 5% under. A circuit with less than a 5% margin seems like it would be flaky over long cables, etc. All of which just convinces me I don't understand the issues well enough to bet on the results. I have a redesigned version of the circuit, but with no way to test either one, the situation is still not satisfactory. If I have to build it without testing, it would be reassuring to at least know what the schematic of the reader-run option is. I have the LT33 drawings, but they don't have a schematic (with parts values) there. More like a picture of the thing, with some cryptic notes about it. Vince