Welch Allyn AudioScope, Service Manual

Page: 21 / 60

- 21 -
__________________________________________________________________________
1.7b Operating Program
:
23300 (Microcontroller type serial
no.9670000 and higher)
Multi-Level AudioScope3
(Microcontroller/non ASIC)
Sequence : Cause: Effect:
1. Manual Switch "ON" Lamp "ON",Ready LED "ON"
2. Manual
Press "START" MICRO activated
3. Logic
U4 pin 9 goes to 3 V activates PT (PreTone) LED (D3)
4. Logic U4 pulses pin 4 U4 ramps U5 (digital pot) to calibrated
level. This establishes feedback
resistance for U3C.
U4 sequentially toggles pin Generates digital base amplitude
19, 20, 21, 22 sinewave at pin TP10
General cycle is repeated for TEST tones : 1000, 2000, 4000, and 500 Hz.
5. Logic U4 pin 8 goes to 3 V activates 1000 Hz LED (D4)
U4 pulses pin 4 U4 ramps U5 (digital pot) to calibrated
level. This establishes feedback
resistance for U3C.
U4 sequentially toggles pin Generates digital base amplitude
19, 20, 21, 22 sinewave at pin TP10
6. Logic
U4 pin 7 goes to 3 V activates 2000 Hz LED (D5)
U4 pulses pin 4 U4 ramps U5 (digital pot) to calibrated
level. This establishes feedback
resistance for U3C.
U4 sequentially toggles pin Generates digital base amplitude
19, 20, 21, 22 sinewave at pin TP10