Amiga CD32 CD-ROM Lens alignment
By Ian Stedman, 18th March 2003, updated 16th April 2010 with a note.
Introduction
This document details how to clean and re-align the CD-ROM fitted to the
Amiga CD32 games console. It should not take more than 30 minutes for a competent person to perform.
Note:
The method specified here involves fiddling with the undocumented laser settings of the CD32 drive. I have been criticised for publishing this information.
The procedure specified here worked for me, use at your own risk.
Before trying to adjust the laser, clean the lens with isopropyl alcohol (IPA) and see if that fixes your problem.
Background
A few years ago my CD32's CDROM drive was not reading discs properly. I cleaned the lens but to no avail. Thinking that it needed adjusting, I opened the drive up and played around. Ok I was inspired by some information on fixing the lens of the Playstation, a procedure I carried out myself.
Once I dis-assembled the CD32 CD-ROM I found some presets and with careful adjustments, I re-aligned the drive and resolved the seeking problems I had. The notes I made (and subsequently lost) later became this guide.
Equipment needed
2 Philips screw drivers, small and medium size to disassemble the CD32 & CDROM.
1 small flat blade screwdriver.
1 cotton wool bud and Isopropyl alcohol (commonly sold as tape head cleaner).
This guide!
Note: The photographs shown in this guide were from my spare CD32 ROM drive, as such there is no audio-mixer panel shown. When I did the actual alignment, I used a full CD-ROM drive.
Disassembling the CD32
- Undo the 5 screws on the underside of the CD32 and the one screw holding the cover of the expansion connector.
- Open up the CD32, placing the CD drive assembly on the work surface with the cables connected.
- Dis-connect the CD32 drive and the headphone/mixer board from the CD32.
- Unscrew the CD-ROM from the CD32, as shown here.
(Click image for a larger view)
- Now that the drive has been removed the metal cover at the top of the drive can be removed. If you look at the drive from the top (the side with the lens), you will see that by carfully prising the case on the right hand side, it will be removed.
- Now re-fit the CD-ROM into the case so that we can align the drive, leave the metal case off.
- Re-connect the CD-ROM and mixer cables to the CD32.
- We can now look at how to re-align the drive. Looking at the drive sideways on you will see the following presets:
(Click image for a larger view)
With the drive re-fitted, they look something like this:
(Click image for a larger view)
I will point out at this stage that I do not know what these names (FEG, TEG, FEB & TEB) mean! My guess is that and 'F' is for focus and 'T' for tracking
but I can not confirm this and there is nothing in the CD32 service manual!
Adjusting the drive (read carefully)
By careful, measure adjustment of the 4 potentiometers mentioned previously you can adjust the drive but you need patience!
Where indicated, only adjust a potentiometer by the smallest amount at a time, it can easily go wrong, you have been warned.
Guide to potentiometer adjustments
Tuning | Affects |
FEG | Seeking of the drive. Mis-adjustment causes a high pitched whine of the drive mechanism. |
|
TEG | Mis-adjustment of this causes complete loss of signal. |
FEB | As for TEG above. |
TEB | This primarily affects audio CDs. Adjust very carefully, especially if it causes CDs to skip. |
I recommend using FEB/TEB for most adjustments of the drive, including slipping of audio tracks.
Adjust TEG/FEG if the drive if the drive appears to spend too much time locating a track.
Load the CD32's built in Audio player and insert an Audio CD.
We will use this to tune the drive. I had my CD32's CDROM drive at 90 degress to the case (to form an L shape) so that I could easily access the adjusting screws. Once the CD has been inserted it will not fall out and I had no problems with the CD playback.
Try playing a CD, does it play correctly?
If no, try adjusting FEB/TEB carefully.
Try skipping to a new track, does it take a few seconds to do this?
If yes, try adjusting TEG/FEG.
When playing a track, does the lens assembly appear to move back and forth slightly?
If yes, try adjusting TEG/FEG.
If you over adjust, FEB/TEB, the CD will skip to random tracks or stop working completely. The other thing it can do is make the CD soound as if it is playing at double speed!
When you are happy with your adjustments, re-assemble your CD32, making sure your re-connect all the cables.
Cleaning the lens
Hopefully by now you have adjusted the lens, before re-assembling the CD32, how about cleaning the lens?
I recommend using Isopropyl alcohol, which is commonly sold as tape head cleaner fluid in your local discount shop. The other item you need is a cotton wool bud to soak in alcohol and then swab the lens.
(Click image for a larger view)
In conclusion
The adjustment method I have outlined here is not perfect but I hope that it allows you to get your CD drive working.
I welcome any feedback by email, click here to send an email
CD32 Drive alignment Version 1.1, 16th April 2010.
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Updated 30 August 2010