Motorola SSETM 5000 service manual VCO TX/RX Unlock, Vco Tx/Rx

Troubleshooting Charts: VCO TX/RX Unlock 9-15

9.10 VCO TX/RX Unlock

VCO TX/RX

unlock

"Sniff"

frequency near

VCO shield

Sniff: Using an inductive field probe as an antenna to measure frequency. Place the probe approximately 1/2 inch away from components to be sniffed.

Frequency		No			No	Check parts
			5V at TP3?			around U1. If
detected?
						OK, replace U1
	Yes			Yes
			Check parts
Check control					No
voltage at			around U2. If			3V at TP5?
TP243			OK, replace U2
							Yes

<0.6Vdc		No			Check if VCO
>11.0Vdc or					is locked using
drifting?				spectrum analyzer
	Yes
Check parts			No		VCO locked?
around U202. If
OK, replace U202
						Yes
					Check
					VOCON board

Remove

VCO shield

Aux. line		Yes	Is pin		No	Remove
4 high for TX			19 of VCOBIC			VCO buffer
or low for RX?			low for RX and			shield (SH302)
			4.5 for TX?
No				Yes
						Check parts
Field Effect Transistor (FET)						around Q302. If
Q210	Q214					OK, replace Q302
			FET		No	Check parts
			drain voltage			around FET. If
			0V?			OK, replace FET

Yes

Bi-polar Transistor (BJT)

Q211 Q215

BJT		No	Check parts
emitter voltage			around U250. If
>1.2V?			OK, replace U250
	Yes
Check parts
around BJT. If
OK, replace BJT

MAEPF-27398-A

6881094C12-A November 11, 2004