22 Dec
2020
22 Dec
'20
5:38 a.m.
On 22 December 2020 at 10:33 GMT, Aaron Jackson via cctalk wrote:
On 22 December 2020 at 08:01 GMT, Christian Corti via
cctalk wrote:
Alright been playing around with that for an hour or so. I think I'm
beginning to understand what has happened.
The ready lamp flashes not when the servo burst is visible, but when the
heads are just before it. Why? Well, I probably set the gain too high on
the read/write module.
... Why did I set the gain too high? Probably both my cartridges are
weak and to compensate for this, I set the read/write module's amplitude
too high during the "Read Signal Amplitude Adjustment" in Chapter 3 of
the tech manual.
I think having this amplitude too high amplifies the noise too much,
which makes the drive believe it's found the first track, but is
struggling to read the servo bursts because they're not actually there
there, hence the slight head oscillation.
Does this sound like a reasonable theory?
If so, I suppose now might be a reasonable time to ask the list if
anyone in the UK has a known *good* cartridge which they'd mind selling
me for a sensible price? I know there aren't too many of them floating
about the UK these days.
Thanks everyone who has given me some pointers so far
Aaron
This message and any attachment are intended solely for the addressee
and may contain confidential information. If you have received this
message in error, please contact the sender and delete the email and
attachment.
Any views or opinions expressed by the author of this email do not
necessarily reflect the views of the University of Nottingham. Email
communications with the University of Nottingham may be monitored
where permitted by law.
On Mon, 21 Dec 2020, Aaron Jackson wrote:
That's very interesting to know. Thanks! I have already performed the
head alignment and they looked well aligned when switching between the
two heads, but I didn't have any luck getting it to lock onto the first
track with the head select jumper in. I'll mess about with this some
more, it is at least reassuring that someone elses drive has displayed
similar behaviour.
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 had almost the identical problem with a RL02 drive from a friend. It
would start and load the heads, but the ready light would flicker or not
even come on. After a measuring session I discovered that if I manually
select the other head, everything would be fine. And if I disabled the
servo motor I could manually lock onto the track on side 0, but then side
1 was out of alignment. So the alignment between the two heads was wrong
and I had then aligned one of the heads so that the two would lock onto
their corresponding track. The drive works fine since then.