
CCS Technical Documentation
Troubleshooting — RF
NPD-4
Issue 1 02/2003
Nokia Corporation Confidential
Page 35
Table 7: RF probing for Cell CDMA and AMPS front end receiver
Probing point
Probing
location on
board
Probed absolute
power (dBm) or gain/
loss (dB)
What to check if RF power not
correct (soldering, shorts, DC
power applied if active, correct
voltage of DC signals, otherwise
replace)
Diplexer (Z805)
out= cell duplexer
(Z803) in.
8, Figure 7
Loss=0.5 dB through
diplexer
X800, L812, C801, Z805, Z803
Cell duplexer
(Z803) out= Alfred
(N750) in
32, Figure 5
Loss=2-4 dB through
duplexer
Z803, L750, N750 (VRX)
Alfred (N750) LNA
out= cell RX saw
(Z751) in
33, Figure 7
Gain=12-14 dB for
high gain mode
(GAIN_
CTL=high. Use RF AGC
status window to
monitor state.),
Loss=-3 to –5 dB for
low gain
N750 (Also ensure BAND_SEL low
as in Table 9. Also IF_SEL low for
CDMA and high for AMPS, as in
Table 9. Ensure GAIN_CTL is high if
RX power is below the LNA switch
point.), Z751, C755, L752, C757,
R764, C753, R768, C756
Cell RX saw (Z751)
out=Alfred (N750)
mixer in
34, Figure 7
Loss=1-3 dB through
SAW filter
Z751, N750, R765, C750, R768,
C756, L757, C758
UHF LO at 1009.62
MHz in Cell
CDMA/AMPS for
channel 384
10D, Figure 7.
Can probe on
top of plastic
to check for
presence of LO,
but won’t read
accurate
power
Approx –3 dBm
Check to see if LO is present. If no
LO is present, check R515, C511,
C501, C532. Make sure there is
2.7V at TP 10B. If voltage is less
than 2.6V, then refer to baseband
regulator troubleshooting. If volt-
age is 2.7V, check G502 at TP 10A
with a FET probe to see if UHF LO is
present. Check that the 19.2MHz
clock is present at TP 10C. If LO is
present but unlocked, check C518,
C508, R508, R503, C509, R550,
and C550. Pay particular attention
to C508, as it is easily damaged. If
LO is present and locked, but
doesn’t appear at TP 10D, then
check R505, R507, L771.