If you want to monitor the servos, you could probably also connect your
scope to the servo lines that feed the actuators and establish that the
drive patterns are not clipping or excessive in size. Tapping the drive whilst
doing this will check.

Hello Jim - I've made a not of this. Thanks. andy

=== Andy Evans ===
Visit our Website:- http://www.artsandmedia.com
Audio, music and health pages and interesting links.

In article , Andy Evans
wrote:
If you want to monitor the servos, you could probably also connect your
scope to the servo lines that feed the actuators and establish that the
drive patterns are not clipping or excessive in size. Tapping the drive
whilst doing this will check.

Hello Jim - I've made a not of this. Thanks. andy

FWIW there are some books on servicing and 'troubeshooting' CD players.
Although the one I have is quite old, and only deals with CD-A players, not
CDROM drives. Might be worth your while looking for books on this, though.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

My interest, though, is not in the theory of creativity. It is to try and help
you develop better kit, and gain understanding in the process.

That's very kind of you. I really must get my scope out and find out how to use
it. I think a good service would be a start. It's a Philips PM3214. Where would
I get that serviced and recalibrated?

=== Andy Evans ===
Visit our Website:- http://www.artsandmedia.com
Audio, music and health pages and interesting links.

On 12 Nov 2004 09:56:31 GMT, ohawker (Andy
Evans) wrote:

My interest, though, is not in the theory of creativity. It is to try and help
you develop better kit, and gain understanding in the process.

That's very kind of you. I really must get my scope out and find out how to use
it. I think a good service would be a start. It's a Philips PM3214. Where would
I get that serviced and recalibrated?


Andy - switch it on, provided it works, you can calibrate it yourself.
It should have a calibration signal that will let you set the gain of
the vertical amplifiers, and adjust the trimmer capacitors in any x10
probes (tweak for nicest square wave).

As for frequency calibration, it is unlikely to be off, and it really
doesn't matter if it is a bit out - you aren't likely to be using it
to measure frequencies.

As for using it - just poke around and see what you see, get used to
setting the timebase to see clear waveforms, and the trigger controls
to keep them steady. And be careful only to clip the ground lead on
the probe to ground points in the circuit.

d
Pearce Consulting
http://www.pearce.uk.com

I'm starting a file called 'scope' for all comments and instructions. I'll
obviously need some tuition. the previous owner suggested a service - he used
it all the time, and used to tap it if something stuck. Sounds like that could
be improved. I think he said they were serviced in ilton Keynes or Watford -
somehwere up there. I'll have to find out. I've also got a signal generator and
another box of some description. this is all ex-Beard Audio when I bought out
the remaining stock when Bill went off on his boat. Andy

=== Andy Evans ===
Visit our Website:- http://www.artsandmedia.com
Audio, music and health pages and interesting links.

On 12 Nov 2004 10:28:22 GMT, ohawker (Andy
Evans) wrote:

I'm starting a file called 'scope' for all comments and instructions. I'll
obviously need some tuition. the previous owner suggested a service - he used
it all the time, and used to tap it if something stuck. Sounds like that could
be improved. I think he said they were serviced in ilton Keynes or Watford -
somehwere up there. I'll have to find out. I've also got a signal generator and
another box of some description. this is all ex-Beard Audio when I bought out
the remaining stock when Bill went off on his boat. Andy

Go round to your mate who tests your amps for some driving lessons -
that'll be hundreds of times more effective than anything you can get
here.

d
Pearce Consulting
http://www.pearce.uk.com

Go round to your mate who tests your amps for some driving lessons -
that'll be hundreds of times more effective than anything you can get
here.

It's his old scope!

=== Andy Evans ===
Visit our Website:- http://www.artsandmedia.com
Audio, music and health pages and interesting links.

On 12 Nov 2004 10:59:42 GMT, ohawker (Andy
Evans) wrote:

Go round to your mate who tests your amps for some driving lessons -
that'll be hundreds of times more effective than anything you can get
here.

It's his old scope!

Then he is the ideal person for the task.

d
Pearce Consulting
http://www.pearce.uk.com

In article , Don Pearce
wrote:
On 12 Nov 2004 10:59:42 GMT, ohawker (Andy
Evans) wrote:

Go round to your mate who tests your amps for some driving lessons -
that'll be hundreds of times more effective than anything you can get
here.

It's his old scope!

Then he is the ideal person for the task.

:-)

BTW I agree with what Don has said about checking the scope.

You could also check that on DC its readings are consistent with your
voltmeter when they are both connected to, say, a battery at the same time.
This ensures that you aren't caught out by a drop in voltage in the scope
affecting the size of its test signal.

If you know the frequency of the test signal you can also look at it with
the scope triggered from the mains ('line'). This gives a rough check on
the frequency that should be good enough for general purposes, and can give
an approximate check of your time scale.

In a 'pro' lab I'd recommend getting a more serious calibration done. But
for normal day-to-day work what Don has outlined should be quite
satisfactory.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

Hi,

In message , Jim Lesurf
writes

I have some CDs with pinholes. However so far as can tell, these have had
them since purchase, and they have not altered. They seem playable with not
audible problems I have noticed. The Philips Red Book spec caters for quite
large holes in the info layer without this necessarily preventing recovery
of the correct sample values.

I recently read an article by M.S. Rohan entitled "When Caruso went
foggy and started sweating" which describes problems with compact discs,
and their suitability (or not) as a long term storage medium. I get the
impression that there are some in the music industry that do not feel
CDs will last as well as the public has been led to expect. "Perfect
sound forever" is a bold claim, after all. We are probably fortunate
that it is so easy to archive the data; we are unfortunate that it is
currently illegal to do so in the UK.

I've also had a number of the PDO Blackburn 'brown rot' discs, and they
have replaced them all FOC when returned to them. However these don't show
holes. Just a brown discolouration of the metal.

I've never seen this first hand, but I have a number of older CDs that
seem to be deteriorating with age (visually at least - they still play
without problems).

I have bought a CD that had mould though. I'm guessing this was just due
to bad storage, and nothing to do with manufacturing. The surface of the
disc was mottled green. Very odd, as the case showed no signs of it.

--
Regards,
Glenn Booth