I had bought a couple of non-working A520 modulators for a new project, however with the advent of COVID-19 and general lack of time due to life I decided I'd just fix them and make use of them.
Of the two modulators I had no picture at all and the other looked like this. However both have the same problem, the MC1377P - Colour Television RGB to Pal/NTSC Encoder.
Opening the case
The A520 is a friction fit case, there are no screws to remove or catches to unclasp. The easiest way to pull the two halves apart is to use a plastic spudger to slowly lever the two halves evenly apart. It is important not to twist the case or lift it unevenly!
You can see here the four legs that hold the two halves together. The small rods insert into the larger hollow rods and hold very tightly.
The next thing to do is the remove the only two screws in the unit that hold the PCB to the bottom half.
Replacing the MC1377P
Replacing the chip is a fairly easy affair as the PCB is single sided. Using a desoldering tool is a breeze and the part just falls out.
As with all DIP replacements it is good practice where you have vertical clearance to solder in a socket.
Lastly lets give it a test. That is so much better.
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