Sharp MZ-3500 User Manual download pdf (Page 82)

M2 3500

c. Power switching circuit

As the signal from the oscillator is amplified through Q7

to Q6 to change current to the transformer T2, it causes

voltage to appear on the base of Q5 (one of components

is cut by Dl), so that the transistor Q5 begins to per

form switching operation in synchronization with the

oscillation frequency. As Q2 is switched, current is

supplied to the emitter side of the transistor Q5, which

produces smoothed voltage through the capacitor Cl

and the coil L2. The circuit composed of D4 and VR1 is

the reference voltage for the -h5 or -H12V supply, which

is used to control the emitter current flowing to the

transistor Q9. The current supplied from Q9 is used to

create Tr3 inactive by the delayed Cl and C2 voltages

which supplied from Tr1-R2-VR1-D3. It goes high with

deactivation of Tr3.

3. Alarm circuit

(Alarm generation circuit)

When power turns off, the voltage accumulated in Cl

and C2 are supplied to the base of Tr2 via Tri ... and

D3, so that Tr2 is kept active and Tr3 inactive for some

times after power off.

Timing chart

- 89 -

1 2 ... 77 78 79 80 81 82 83 84 85 86 87 ... 115 116

No comments

Sharp MZ-3500 User Manual Page 82