RL02 Tracking (Aaron Jackson)

Chris Quayle syseng at gfsys.co.uk
Tue Dec 22 14:24:19 CST 2020

On 12/22/20 18:00, cctech-request at classiccmp.org wrote:
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> Today's Topics:
>     1. RL02 Tracking (Aaron Jackson)
>     2. Re: RL02 Tracking (Aaron Jackson)
>     3. Re: RL02 Tracking (Jon Elson)
>     4. Re: RL02 Tracking (Josh Dersch)
>     5. Re: RL02 Tracking (Aaron Jackson)
>     6. Re: tty and video displays (Jules Richardson)
>     7. Re: Keyboard storage (Guy Sotomayor)
>     8. Wordperfect 6.0 for DOS (Van Snyder)
>     9. Re: RL02 Tracking (Noel Chiappa)
>    10. Keyboard storage (Alan Perry)
>    11. Re: Keyboard storage (Warner Losh)
>    12. RE: Keyboard storage (Ali)
>    13. Re: Keyboard storage (Alan Perry)
>    14. RE: Keyboard storage (Ali)
>    15. Re: Keyboard storage (Alan Perry)
>    16. Re: Keyboard storage (Guy Sotomayor)
>    17. RE: Keyboard storage (ED SHARPE)
>    18. Re: RL02 Tracking (Christian Corti)
>    19. Re: Keyboard storage (Patrik Schindler)
>    20. Re: RL02 Tracking (Aaron Jackson)
>    21. Re: RL02 Tracking (Aaron Jackson)
>    22. Re: Keyboard storage (Alan Perry)
>    23. Re: Keyboard storage (Bill Degnan)
>    24. Re: Ouch, but 2 Perqs out. (Why 42? The lists account.)
>    25. Re: Ouch, but 2 Perqs out. (Why 42? The lists account.)
>    26. Re: Ouch, but 2 Perqs out. (Tony Duell)
>    27. Re: Ouch, but 2 Perqs out. (Tony Duell)
>    28. Re: Ouch, but 2 Perqs out. (Chris Zach)
>    29. RE: Keyboard storage (Fred Cisin)
>    30. RE: Keyboard storage (ED SHARPE)
> ----------------------------------------------------------------------
> Message: 1
> Date: Mon, 21 Dec 2020 19:08:14 +0000
> From: Aaron Jackson<Aaron.Jackson at nottingham.ac.uk>
> To: "cctalk at classiccmp.org"<cctalk at classiccmp.org>
> Subject: RL02 Tracking
> Message-ID:<91bim8vyo2q.fsf at mimas.cs.nott.ac.uk>
> Content-Type: text/plain; charset="iso-8859-1"
> 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!
> Aaron


One thing I would check is the motor bearings. What happens on electro
mechanical assemblies left in store for years is that ball bearing
grease lube dries out and hardens, resulting in lumpy rotation and
increased friction that can be detected by rotating the spindle by
hand. RLxx series drives were very reliable typically, but the head
movement assy is pretty cheap and cheerful. Converting spindle to
linear movement, minimum parts count, dc brush brush motor, means that
all the bits need to be smooth in operation, with no stiction anywhere
in it's travel.

I would take the motor out and if it can't be stripped to clean the
bearings, use a dab of light clock oil to relube. Also, check the
brushes and clean / polish the commutator. Any other ball bearings
in the path, same process. DC brush motors can be a nightmare for
that sort of precision positioning application...


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