Motorola ASTRO XTL 1500 Detailed Service Manual page 156

Troubleshooting Procedures: Standard Bias Tables
Table 4-18. Standard Operating Bias: Audio Lines (Continued)
Nominal Value
9.2 V
2.84 V
1.4 Vdc to 25 Vdc
(needs ext. cap)
0 V
Note: The Mic_Hi audio overrides Aux_TX/Aux_Mic audio, and the speaker is always muted.
0 V
26v peak-to-peak
@volume= 15+
Note: Never ground speaker lines. They are differential, not single-sided.
Use an oscilloscope probe on "Spk+" and oscilloscope-probe GND on "Spk-".
2.85 V
2.84 V
1.3 V
0 V or 5 V
Note: Do not KEY UP unless the board is inside a chassis.
6815854H01-A
Signal Name
Aux_Mic = [ A(tx) ]
(transmit audio)
Aux_PTT = [ PTT ]
Aux_TX (audio input)
Aux_RX (audio input)
Speaker +
Speaker -
Speaker +
Speaker -
Monitor
Audio_PA_Enable
RX_Filt_Audio = [A(rx) ]
(receive audio/audio
output)
Chan_Act = [A(p) ]
(qualified audio
presence)
HUB
Range/State
Expects 300 mV input
(APCO default)
Expects 80 mV input
(motorcycle use)
Idle = High
Active = Low
Hard-wired PTT, which
will mute or unmute
Aux_Mic line
300 mV line-level
(no mic bias)
300 mV line-level
(Audio PA In)
Muted (output)
Muted (output)
Unmuted (output)
Unmuted (output)
Idle = High
Activate = Low
300 mV line-level output
Idle = Low (0v)
Active = High (5 V)
This pin causes the
control head to send
SB9600 message to the
radio, indicating when
HUB is attached
Probe Locations
J0401-6, J2-23
J0402-24, J2-16
J0401-7
J0401-8
J2-21, U204-4
J2-20, U204-6
J2-21, U204-4
J2-20, U204-6
J2-22
Q0200-1
J2-21, TP0204
J2-13
P502-3
June 15, 2005
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