21 Dec
2020
21 Dec
'20
3:08 p.m.
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
backwards.
Aaron
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