5.2 No back-light at all
If there is no LCD back-light at all, check that you have installed R48, and also check that
you have properly installed the LCD connector between the main PCB and the LCD
module.
5.3 A row of blocks appears on the top row
If you see a row of blocks along the top of the LCD module, and the bottom row is empty,
this means that the microcontroller has not communicated with the LCD module.
Check that your IC2 microcontroller is correctly installed in its 28-pin socket, with the correct
orientation (dimple on the chip matches the dimple on the socket and the PCB silkscreen).
Check that all of the pins of IC2 are correctly inserted in the socket, not bent.
5.4 DC voltage readings
The following table lists the DC voltage read at various points around
the circuit. This may aid troubleshooting. The voltage measurements
were made using the in-built DVM, in menu item 9.1. These
measurements were made using a 12V power supply.
Where an IC pin number is mentioned, remember that pin numbers
start from the top left (just to the left of the dimple at the end of the
chip) and are counted anticlockwise from there (see diagram of 8-pin
IC for example, right).
Where “left”, “right”, “top” and “bottom” are mentioned, they assume the PCB is orientated
in the normal way.
All measurements were made probing the PCB from the top side. In some cases, poke the
wire to touch the pad of a particular capacitor or resistor.
References to the pinout of transformer T1 use the nomenclature indicated in the diagram
(right).
In many cases these measurements may not
exactly match your own. In particular if you use a
power supply other than 12V, then voltages
which are derived from the 12V supply line will
be different. For example, bias voltages on op-
amps which are biased to half the supply rail.
Bear in mind that in some of these
measurements, the act of measurement will
itself change the measurement. The “input
resistance” of this DVM is only 13.3K (R56 and
R57 in series, assuming high input resistance of
the microcontroller pin). If you were to make
these DC measurements with a high input
resistance “real” DVM rather than the inbuilt
DVM of this radio transceiver, these measurements would change. Again: if your
measurement is in the right ballpark, do not worry if it differs from these.
102
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