Motorola V300, V500, V600 Service Manual

Triplets Repair Map – Transmit

(1) If you suspect no Tx at M3

With PCB in suspend mode, set 62ch-902.4Mhz and power level 15 then enable Tx mode.(700ch - 1747.8Mhz -DCS) Check 902.4Mhz at M3.

NB.If units powers down after above command,it is possibly due to defective PA.To check for this,remove the PA and ensure there is 902.4Mhz signal at U80.(1747.8Mhz at U81)

(2) If output at M3 is missing :

Check for 902.4Mhz at L5 (1747.8Mhz -DCS)

If this signal is present then the problem is most likely around the Antenna switch connector(J1).

(3) If the signal at L5 is missing :

Check for 902.4Mhz at U80 Pin2 (1747.8Mhz DCS at U81 Pin2).

If this signal is present check :

•PA power supply PA_B+ at C50,C51

•U50(PA)

•L70, R70

(4) If the signal at U80 Pin2 is missing :

Check for 902.4Mhz at U150(Algae) Pin38 (1747.8Mhz at Pin39 -DCS).

If this signal is present check :

•U80, U81 for dry joints,damage

(5) If the signal at U150 Pin38 is missing :

Check for power supply and control signal of U150:

•RF_REG at C173 5a

•	SF_REG_OUT at Pin45 (C154) 5b	a,b,c
•	EXC_EN at Pin36 (C177) 5c

If above signals are correct then replace U150.

(6) If the signal at U150 Pin38 is still missing :

•Check the control path TX_TUNE from U800(Neptune) D4 to U150 Pin44: R160, R161, L161, C162, R162, …

•Check the feedback path from U50 Pin 15 to U800 B10

for discretes dry joint,damage,missing.

If not effective then the issue is most likely a U800 problem. Replace U800.

U80 Pin2

a RF_REG

TX_TUNE

(RX_TUNE for RX)

M3		L5	U150 Pin38 c EXC_EN		b SF_REG_OUT
		Signal Path Key
	Red signal path represents Tx		Blue signal path represents Rx
		Green signal path represents TX_TUNE