User Guide

Technical Documentation

NHB–3

PAMS

Troubleshooting

Original 26/97

Page 32

Reference oscillator VCTCXO

Test point Position Frequency *Level Note:

6 V800 DC ~2.5V

7 N820 pin 8 26MHz 1V

ref

Bias V801 C DC 3.2V Bias

Bias V801 B DC 1.8V Bias

Bias V801 E DC 1.1V Bias

– check the crystal and other components in oscillator circuit.

VHF Synthesizer Malfunction

Voltage from Do IF

Test point Position Frequency *Level Note:

8 C823 DC 2.5V (all channels)

Voltages of N820

Test point Position Frequency *Level Note:

9 N820 pins 1,20 DC 4.0V Pow. supply

10 N820 pins 2,19 DC 4.6V Charge pump

Biasing voltages on VHF

Test point Position Frequency *Level Note:

Bias V841 C DC 4.3V Bias

Bias V841 B DC 3.2V Bias

Bias V841 E DC 2.5V Bias

Bias V840 C DC 2.4V Bias

Bias V840 B DC 1.5V Bias

Bias V840 E DC 0.8V Bias

– Check the components surrounding V840 and V841, and make sure that

V842 has been soldered as the component location picture shows it.

– Check the following components: R827, R828, R840, C823, C824, C830,

C840