Here's the solution that shows the particular components that might get damaged when the Nokia 1616 and nokia 1800 having a signal problem issues. This repair solution guide shows the layout of a components and particular test spots to check during servicing NO network signal problem.
Nokia 1800 and Nokia 1616 No network signal Solution
The RF circuit is located at the bottom of the pcb board. The RF clock oscillator and the RF power amplifier chip is a good spots where to begin checking up. Before trying to remove and replace this ic component, you may check the corresponding Vbat voltage first on the chip capacitors indicated on the picture. This Vbat voltage is a power supply voltage that came from the battery positive terminal. The TX chip resistor that have resistance value of ohms is where a part of TX signal flows across to it from the RF clock oscillator, you may check it also.