Fgu Troubleshooting Aids - Motorola ASTRO Digital XTL 5000 Detailed Service Manual

4-24
Table 4-14. VCO Frequency Calculation and Switching Logic (700–800 MHz) (Continued)
MODE Frequency
Tx (TA) 851.0125 -
Tx (TA) = Talkaround Mode
Tx(RPTR) = Repeater or trunked
3. Continue troubleshooting by using the Fail 001 troubleshooting chart in Chapter 5.
4.9.2

FGU Troubleshooting Aids

The following illustrations are additional service aids for troubleshooting the frequency generation
unit.
• Figure 4-10 on page 4-25
unit.
• Figure 4-11 on page 4-26
• Table 4-15 on page 4-26
• Figure 4-12 on page 4-28
IC U6751.
May 25, 2005
Troubleshooting Procedures: 700–800 MHz Main Board Troubleshooting
Radio VCO
Frequency
(MHz) Formula
F(U6754 osc2) =
868.9875 Fc
is a block diagram of the DC distribution for the frequency generation
is a block diagram of the frequency generation unit.
describes the function of pins on the LV Frac-N IC U6751.
is a waveform representation during programming of the LV Frac-N
VCO
AUX AUX
Frequency
1
(MHz)
851.0125 - Low HIgh
868.9875
AUX AUX
2 3 4
Low Low
6881096C74-B