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Old 21st Aug 2019, 9:48 pm   #231
SiriusHardware
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Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 11,482
Default Re: MK14 schematic revisions

There's a fine line between taking a keen interest and outright hassling someone so I've resisted the temptation to ask Slothie how he is faring with his latest repro PCBs.

On my (original) cassette interface I see that I changed C1, the audio input capacitor, to a lowish value polystyrene type which would have been more at home in a radio project. The obvious intention was to attenuate the input and shave off the low frequency end of the incoming, so maybe I had problems with mains hum and low frequency rumble coming out of the particular tape recorder that I used. SOC recommended using battery powered recorders, as you have pointed out.

One other thing to watch for on original MK14 cassette interfaces, the PCB screen printing for the orientation of the diode D1 was originally the wrong way around, although I believe the circuit diagram always showed it correctly oriented - but if anyone happens to buy an original example it might be worth checking the orientation of that diode just in case the diode was inserted as per the screen printing. Later runs of the cassette interface PCB may have had that error corrected, as well.

Incidentally the (original) diode on my interface is ... a 1N4148, identified by rings in the resistor colour code rather than with printed numbers as per more modern versions.
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