NEC DB2000, Service Manual

Page: 104 / 199

Part 4.2: Transmitter RF Levels and Checks
Using a suitable high frequency probe measure the RF levels at the relevant
points shown in fig 4.1 and compare your measurements with those shown in the
diagram. If there are any major differences between the readings taken and those
indicated then further investigation of that particular point will be required. It will
also be necessary to ensure that all the following power supplies and signals are
present which control this part of the transmitter circuit:-
1. GSM_TX ( Control signal from Superchip which switches 2.85V through to
3V_G_TX.). See figure 4.3.
2.
PCN_TX ( Control signal from Superchip which switches 2.85V through to
3V_P_TX.). See figure 4.4.
3.
3V_G_TX ( A 2.85V supply which feeds parts of the GSM TRX path).
See figure 4.5.
4. 3V_P_TX ( A 2.85V supply which feeds parts of the PCN TRX path).
See figure 4.6.
5. GSM_ON ( Control signal from Superchip which switches 2.85V through to
GSM_PRE_ON). See figure 4.7.
6. PCN_ON (Control signal from Superchip which switches 2.85V through to
PCN_PRE_ON). See figure 4.8.
7. PRE_ON (Control signal from Superchip which enables 2V8_RF2 through to
GSM / PCN_PRE_ON). See figure 4.9.
8. GSM_PRE_ON (A 2.85V supply which feeds parts of the GSM TRX path).
See figure 4.10.
9. . PCN_PRE_ON (A 2.85V supply which feeds parts of the PCN TRX path).
See figure 4.11.
10. TIPI,TINI,TQPI,TQNI (TX I and Q signals which are modulated onto an IF of
180/270 Mhz by the W2013 - IC100). See figure 4.12.
11. TXP/TXP_MOD (Burst control profile from Superchip to control power ramp
characteristics). See figure 4.13
12. V_ERROR ( Feed back loop control for P.A. regulation). See figure 4.14 / 4.15