"David C. Partridge" bravely wrote to "All" (14 Nov 05 20:38:19)
--- on the heady topic of " Monostable divide by 5 not working."

DCP Reply-To: "David C. Partridge"
DCP Xref: core-easynews sci.electronics.repair:348583

DCP If I were starting from a "blank sheet", I probably would use a
DCP digital divider chip or several. BUT, this is an attempt to repair to
DCP a venerable piece of test equipment (Tektronix 184 time mark
DCP generator), which I'd like to keep pretty close to original ...

DCP TIA
DCP Dave


Geez, you guys, this student just wants us to do his homework for him!
Actually, the circuit is simply a monostable which is not retriggerable.
Basically, it's a pulse stretcher. It starts by discharging the 0.1uF
cap through the base resistor of Q2. Because the base is driven hard
negative, a series diode has been added to protect Q2 from reverse
bias breakdown.

The trouble with the circuit is that the input pulses might not be
properly biasing Q1 when high or low and then the trigger point is
constantly changing. Also if the input is driven through a capacitor
then its time constant may be further randomizing the trigger point.

A*s*i*m*o*v

.... When I was your age, we carved transistors out of wood.