Amiga CD32 drive unit adjustment & circuit analysis

The purpose of this video is primarily to give other people an idea of how I adjusted this Amiga CD32 drive unit to have it read CD-R discs really well, which it wouldn’t do before the adjustment.
However, a good understanding of how the drive unit works is essential in order to be able to make the adjustment correctly. Therefore, this is a very in-depth video that covers not only the adjustment procedure itself, but also all the theory that goes behind it.
The following is included in the video:

– Disassembly of the Amiga CD32 drive unit
– Teardown & identification of parts
– Explanation of the signal paths
– Reverse engineering
– Schematics & block diagrams
– Servo system theory of operation
– In-depth circuit analysis & explanation
– Practical demonstrations showing different signals on a scope
– Adjustment setup & preparation
– The adjustment procedure, covering FEG, TEG, FEB, TEB and laser power adjustment
– Presenting lots of scanned-in documents and notes

A lot of the information presented in this video can be applied to any kind of CD player and CD-ROM unit, since the topology behind them is usually the same, only with some minor differences between brands and models. It’s also very likely that most of the information being presented here can be applied to different types of DVD-based systems as well.

Here is an index of the video content for your convenience:

00:00:00 – Introduction
00:05:15 – Disassembly of the CD32 drive unit
00:09:07 – First look at the main controller board
00:10:14 – Teardown starts
00:10:52 – Talking about the pickup unit
00:19:26 – Talking about the laser power potentiometer
00:22:00 – The basic topology of the focus control
00:28:15 – PS2 pickup actuator teardown and demonstration
00:49:49 – F…. E…. G…. ?
00:50:48 – Theory of operation; circuit signal paths
01:01:14 – Schematics, block diagram & general circuit analysis
01:24:29 – More in-depth circuit analysis
01:58:06 – Test your analytical skills
01:59:59 – Some more documentation
02:03:03 – Test your analytical skills: Presenting the answer
02:05:26 – Adjustment preparation
02:18:55 – Talking about the adjustment procedure
02:35:29 – Looking at the signals on a scope; practical demonstrations
02:44:14 – FEG adjustment demonstration
03:07:14 – Constant Linear Velocity
03:08:31 – Looking at the signals with a CD-R in the drive / doing adjustments
03:24:10 – Listening to the whining sound of the actuator coils
03:27:03 – Adjusting FEB using the multimeter technique
03:36:47 – FEG adjustment* (NOTE: Incorrect scope settings! Watch from 02:44:14 instead!)
03:42:55 – TEG adjustment
03:45:54 – Talking about the laser diode power adjustment
03:52:29 – Laser diode power adjustment & practical demonstration
04:00:17 – Comparison between an original and CD-R disc & final thoughts
04:06:33 – Pictures of scanned-in notes and other documentation

*NOTE:
I am doing an adjustment of FEG starting from 03:37:53 in the video.
However, at this time in the video, I forgot to set the scope back to the right timebase, and I’m also using a CD-R for this adjustment although using an original audio disc is better. So this part should really not be included in the video since it’s not a good adjustment technique. However, I realized this after already having uploaded the video to YouTube, and there is no way I’m going to edit, render and then upload the whole video again.
A correct way of adjusting FEG is still included in the video, which can be found starting from 02:44:14.
So as for the FEG adjustment, please disregard from what is shown in the video between 03:36:47 and 03:42:55.
After shooting this video, I double-checked the adjustment using other scope settings.

Datasheets:

Sony CXA1372Q
http://pdf.datasheetarchive.com/datasheetsmain/Datasheets-32/DSA-626775.pdf

Sony CXD2500BQ
http://pdf.datasheetarchive.com/datasheetsmain/Datasheets-25/DSA-483145.pdf

Sanyo LA6530
http://pdf.datasheetcatalog.com/datasheet/sanyo/ds_pdf_e/LA6530.pdf

Sanyo LA6520
http://pdf.datasheetcatalog.com/datasheet/sanyo/ds_pdf_e/LA6520.pdf

Fujitsu MB3771
http://pdf.datasheetcatalog.com/datasheet/FujitsuMicroelectronics/mXwutvt.pdf

Feel free to ask questions and leave any possible corrections in the comments section below.

Some “fun” facts:
After editing, it took over 44 hours for my computer to render this whole video in 1080p. Yes, I timed it.
Also, during the first two rendering attempts, my buggy video editor froze halfway through which forced me to initiate rendering several times over. So, I expect the total rendering time for this video to be close to 100 hours. Crazy, isn’t it?
Luckily enough, I at least had the chance to use my friend’s 100 Mbit internet connection to upload the video to YouTube. The whole 18.3 GB file was uploaded in an incredible 40 minutes! It would probably have been a nightmare to upload it at 3 Mbit/s (in reality 2.2 Mbit/s) using my own ISP.
I think I will try to keep my videos a bit shorter in the future… 🙂

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