VK VK4500, Service Manual

Page: 73 / 81

VK Quality Group GSM C/S
☞
☞
TX Power Trouble (E
TX Power Trouble (E
-
-
GSM)
GSM)
START
Check
DCXO
X601 pin 1, 3 26MHz X-Tal.
Frequency = 26.00MHz
Signal
≥
1.0
Vp-p
Check
Transceiver
U603 pin 4,5,6,7
I/Q signal
≥
DC 1.35 ~ 1.70Vp-p.
Check :
• X601 soldering.
Replace X601 if defective.
Check :
• U603 soldering.
• V250G
• S/W.
Check :
• U603 soldering
• U603 pin 11 DC 1.8V
±
5%
• U603 pin 25,26,29,28,12,13 DC 2.8V
±
5%
Replace U603 if defective.
NO
YES
YES
YES
NO
NO
Set
• Phone : Test mode
62CH, 7level setting (TCH)
62CH, -60dBm setting (BCCH)
• Spectrum analyzer as shown in Remarks.
• Oscilloscope as shown in Remarks.
Remarks
1. Spectrum analyzer : SPAN = 1MHz
RBW = 3MHz
VBW = 1MHz
Press the trace key of spectrum analyzer on checking test
point and press the max hold key of spectrum analyzer
2. Oscilloscope : 500mV/div, 2ms/div
3. RF Cable Loss : about 0.3dB (KAE Cable)
Check
Transceiver
U603 pin 15
Frequency & Power.
Frequency = 902.4 MHz
Power
≥
7 dBm
GO to A