chip and this is shown by scope input readings to the chip (normally clock @ 4volts & reset ramp of around 3 volts) being clamped at below 1 volt.Indicating that the chip inputs have gone low impedance and the chip needs replacing.Often customers use flux on the boards when soldering which unfortunately has an acid content and therefore adds many unwanted resistors to the circuit.This condition can be detected visually with residue on the boards.Jobs began his electronic journey building Note that the coder circuit will run without the IC plugged in.it runs at around 1 KHz which can be seen at the yellow output wire on a scope, or even heard using a crystal earpiece.With the on the bench, with about 25 cm of aerial, pin 3 or the base of the transistor will show around 0.1 volt of mixer output.
The very first Micron transmitter circuitry that I assembled (around 1970) was actually fitted into a redundant commercial transmitter case and sticks.
I often made sure that the receiver board was getting 4volts supply from the decoder board (or slightly more,) but beyond that always used the scope to prod around during faultfinding.
The setting of the IF coil however is critical to a quarter of a turn to get any response at all from the servos.
The transistor gives around 10/12d B gain when fitted correctly.
If you have an oscilloscope, the following can be checked.