Even with bodge in place from #7, output frequencies of cassette port are slightly low, ie 2.31kHz instead of 2.4kHz for a mark.
This seems to be because of the values for the RC network on the reset input of U3, R2 and C4. Replacing R2 with 1K0 (instead of 3K9) seems to resolve the problem.
Even with bodge in place from #7, output frequencies of cassette port are slightly low, ie 2.31kHz instead of 2.4kHz for a mark.
This seems to be because of the values for the RC network on the reset input of U3, R2 and C4. Replacing R2 with 1K0 (instead of 3K9) seems to resolve the problem.