Intermittent black squares printing from Pioneers to 82240B

[Geoff Quickfall]

It is beginning to sound like a noise problem. Either to much data (black square) or to little data (missing print or space command)

So the noise is being interpreted two ways, ignored (missing) or printed (black square). Internally the oil filled caps filter noise and would be my first suspect in the hardware. Especially since the self test functions. Of course the self test prints code directly from the rom therefore no IR test is involved so my second thought would be the IR diode or a cap in that circuit.

Diodes have a shelf life, but up in the 'I won't see it in my lifetime' age.

So now that you have ruled out positional error (too close, too far, receiver and transmitter angles) it would seem that its receive range has narrowed considerably. Again capacitors come to mind as an aging component.

Geoff