RL02 Tracking

Aaron Jackson Aaron.Jackson at nottingham.ac.uk
Mon Dec 21 17:08:04 CST 2020

On 21 December 2020 at 19:08 GMT, Aaron Jackson via cctalk wrote:

> Supposedly if the main drive motor is bad it will emit noise and cause
> the tachometer (just a coil of wire on the head carriage) to produce
> spikes. Mine does look quite noisy but I'm not sure what's causing it. I
> would expect that if it was picking up noise, I'd be able to detect this
> with my oscilloscope probe by putting it close to the motor, but I
> can't. Any ideas?
> Also, thanks to pjustice on irc who suggested checking the spindle
> grounding button. Mine is very worn out but I've been able to apply some
> pressure to it from the under side which reduces the resistance of the
> spindle to ground, from 400 ohm to 0 ohm. This didn't make the situation
> any better though.

This signal appears to be normal and traces back to the seek control
ROM. The question is what causes this output to become high.  Presumably
the 'tachometer AC noise check' does not account for whatever the issue
is with my drive.

Will probe the rest of the ROM outputs tomorrow and continue to trace


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