Improving tape loading on Minstrels

Dave Curran on the Tynemouth Blog discusses improving the tape data loading circuitry for the Minstrel 4, a Jupiter Ace compatible Z80 computer kit running Forth with an expansion slot for RC2014 modules.

I had a brilliant idea, or at least I thought so. It seemed really neat, and it worked very well in certain cases, but not all, some needed various values tweaked to make it work, others just wouldn’t work due to the signal level.

I tried various logic gates last time with different input thresholds, but most of those require too high an input. I think the best option is going to be a comparator as that can have a variable threshold which can be set to suit the input source.

To that end, I am going to fit a variable resistor labelled “Threshold”. This will allow the user to set the threshold level of the input to suit their particular input source.

When set horizontally to the left (about 9 o’clock), should be about right for many cases, and 8 to 10 o’clock is probably the range for most things.

See a detailed engineering analysis in the post here.