Motorola T720PA Service Manual

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nsumer Solutions & Support

US Competency Center
600 North US Highway 45
Libertyville, Illinois 60048

Website: gs.mot.com

FIELD SERVICE BULLETIN

FSB Number: LVCCFSB2004-101
Author: Hien Huynh
Date: April 30th, 2004
Total No. of Pages: 3
Subject: GSM T72x – PA Rework.
Model Affected: T720, T720i, T721, T722.
Level of Repair: 3

Problem

Field service in Asia & EMEA has highlighted a “No Power-up, No TX or Short
Battery Life” issue. In the analysis of PA it was found that the (Source to Vcc),
PA_B+ pin 6, 11, and / or 16 are shorted to ground. Symptoms show an
excessive current draw of 500mA to 1.5 Amps at power up. Also, MFAL and
supplier analysis show the GCAPIIIE93, PGND was burned. Supplier analysis
result show if input voltage is more than 13V, pulse with more than 1ms, it can
damage the IC.

Solution

Design change has proposed to replace C7001 from 10uF(2113928C12) with a 6.8V Zener
Diode ( 2113928Z11) and increase C7000 from 10uF(2113928C12) to 22uF capacitor
(4809788E17). Zener Diode is to prevent over voltage pulse surge from protection circuit.
22uF capacitor will act as original 2 x 10uF capacitors to st able the B+ voltage.

Field Service Action
Customer Returns:

When servicing GSM T72x customer returns, it is suggested that the part
changes be implemented as shown in picture below:

(1) Check the PA- U400 (5109908K66) and U3000 (5109879E83) GCAPIII to

make sure that they are in normal operation.
(2) Replace C7001 with 10uF(2113928C12) to a 6.8V Zener Diode (2113928Z11)
(3) Replace C7000 with 10uF(2113928C12) to a 22uFcapacitor(4809788E17).
(4) Reassemble the PA shield, then the unit
(5) Re -phase.

MOTOROLA INTERNAL USE ONLY Page 1

`

Co

nsumer Solutions & Support

US Competency Center
600 North US Highway 45
Libertyville, Illinois 60048

Website: gs.mot.com

(2)ChangeC7000 from 2113828C12(10uF)

to 4809788E17(22uF Capacitor)

(1)Remove the PA shield

(3)Change C7001 from 21138 28C12 (10uF)

to to 2113 928Z11(6.8VZener diode)

Service Inventory:
N/A

Service Entry Codes

Please ensure that repairs of this type are logged in the service database as
follows:

Asia Codes:
Fault Code: 03 Short Battery Life

04 Can’t Power up / Power Failure

MOTOROLA INTERNAL USE ONLY Page 2