RL02 Tracking

Aaron Jackson Aaron.Jackson at nottingham.ac.uk
Mon Dec 21 13:08:14 CST 2020

Hi everyone

I've posted a few times over the years about RL02 drives and my
difficulty getting them working (no luck so far!). I've spent the past
few days working on one of them and have made some progress.

The status currently is that the heads will load, and the ready lamp
flashes as the heads wobble back and forth very slightly, trying to lock
onto the outer servo guard band. Probing TP2 of the read/write module, I
can see the S1 servo burst flash (roughly in time with the ready
lamp). If I disconnect power to the servo motor, I can manually move the
head onto the outer guard band (less than a mm away) and monitoring the
position signal (TP15 on the drive logic module) shows this to be close
to 0. So, I'm very confused.

I've worked through chapter 3 multiple times...

- voltage checks - all good
- sector transducer output check - all good
- sector pulse timing check - all good
- read signal amplitude check and adjustment - all good
- positioner radial alignment - required some tweeking but is good now
- head alignment - looks good to me
- spindle runout check - a little noisy but within spec
- position signal gain check - looked ok
- tachometer ac noise pickup check - this one didnt look so good

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.

Still, the situation over all is much better now than it was last time I
looked at the drive (over two years ago now I think). Previously the
heads would attempt to load and then the fault lamp would come on
immediately. At least now it's trying to lock onto a track. I have the
same results with two cartridges (which is all I have!).

If anyone has any ideas I'd love to hear them!


(Sorry, as usual, about the footer appended by my university.)

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