it's a Commodore...stereo? actually it's an Amiga computer in disguise!

it's -- zero o'clock.

it boots! and it wants a CD.

oh it speaks "American"

let's take it apart. some familiar chips inside.

underneath the Amiga board is the CD-ROM drive and a PCMCIA slot!

it uses a CD caddy. i can't remember if i have one of those somewhere.

huh look a bad solder joint

hmm that is an odd keyboard connector

the daughterboard has some really odd flash memory chips in ceramic packages.

this flash daughterboard was apparently only included with the developer units. wow!

so it did not come with the remote. this should be ok because apparently they are common; commodore built way too many of them so they shouldn't be hard to find cheaply on ebay.

cheaply on ebay. 🤦

guess i'll have to wait for one to show up at a reasonable price.

in the meantime, i discovered that someone already has an arduino sketch to generate the raw codes. gist.github.com/bengtmartensso…

it uses IRremote (github.com/z3t0/Arduino-I…). funny, the name at the bottom of the readme looks familiar. oh, it's @kenshirriff! nice work man.

sadly my IR LEDs are not well sorted. time to figure out which ones are are LEDs and which ones are photodiodes 😂

hmm not bright enough

a bit better.

found a brighter IR LED but the CDTV ignores the signals. 🤔

time to dig in. is the IR decoding microcontroller receiving a signal?

yes it is. maybe the bit timings are wrong.

the bit timings WERE wrong (in the Arduino sketch). here are the correct values (taken from sourceforge.net/p/lirc-remotes…)

now i can set the time. 🤗

swapping out the LED with this old Fairchild FPE530. this one also works.

i had borrowed the LED from this remote. 😂

so the CD-ROM drive in this computer doesn't work. looks like a bunch of the capacitors are bad or marginal. i'm just going to replace them all.

this capacitor is clearly bad. capacitance reading is way off, and you can see some residual electrolyte on the PC board.

this one is also bad, but it is subtler. the capacitance is lower than what it should be, but the ESR is way high! this is why you have to use a meter that can measure ESR. or just shotgun it and swap all the electrolytic caps on the board.

checking the power supply too.

whoops, glad I checked!

cleaning the board with a solution of baking soda and distilled water. it foams, so there's definitely some neutralizing going on. capacitors are on order.

new capacitors arrived. time to solder them in!

done! i hope i remember how to put it back together

recapped the CD-ROM drive board. i hope i remember how to put THAT together!

the CD-ROM drive is wider than the usual 5 1/4" drive bay.

manufactured January 1991.

reassembled it most of the way... and it won't boot anymore. i half expected this to happen. 😂

put this in, and now it works. go figure.

the CD player controls are super fancy

so I found a data disc that works (I booted from a floppy drive). this machine is really picky.

so I did a bunch of experiments. different discs, different CD-R drives.

and by burning a disc in my laptop using the 10x speed setting, I can get to this screen. but no further, it reads for a while and then gives up.

if i put in a disc that is readable by the drive but has other, non CDTV content on it, the loading screen just turns red like this.

so i know it's able to read at least some files on the disc, but for whatever reason it's not able to complete loading the software. 🤔

here we go again, time to take out 627446 screws

the adjustment pots are all on the top of the board, but at least they have labels on the bottom side. but that's not what i'm looking for.

I'm trying to find a test point amidst a sea of test points

found it! this is the amplified signal from the optical sensor. the 118mV signal is from a stamped disc. now to try out some of the other discs I made...

this is from a high quality Memorex disc burned on my desktop PC. amplitude is worse and there appear to be some lower amplitude areas on the track. this disk is not readable by the drive.

similar issues with a Verbatim disc. also burned on my desktop PC.

this generic (couldn't find a brand, probably Fry's special) disc did better. also burned on my desktop PC.

same generic disc but burned in my laptop at 10x speed. 129mV. so the burner and burn speed makes a difference!

(119mv for the last one, oops)

high quality Verbatim media but burned in the laptop at 10x. it's only 80mV but the drive still reads it! the plot thickens--amplitude isn't everything.

I've moved over to the focus error signal. this little blip happens when the head crosses over the spiral track once per revolution. signal is from a pressed disc.

Verbatim disc from my desktop PC. looks like it's having a little trouble focusing.

now the tracking error signal. the non-working burned disc has slightly less tracking error magnitude than the pressed disc! that's odd.

since the focus and tracking seem to be ok, let's look at the data signal. after coming out of the preamp, it goes through this 339 comparator and becomes the /TEC signal.

it goes into this chip, which is a standard cell gate array. *sigh* it could be anything. maybe CDR? time to prove some more. really what I want is the recovered clock signal.

previous chip was for servo control. this chip, the M50422, does the actual decoding.

found a block diagram. here's the data slicer and PLL circuit. looks like the loop filter uses external parts, so i may be able to probe it and see if it is having trouble locking to the incoming signal.

pll filter looked steady. I moved on to the crc flag output. each little burst here is a set of 8 pulses at 3.57MHz. does this for every disc but the unreadable discs have more jitter on the 135us interval. not sure what that means yet

looking at the error flag ST1 output now. the pressed disc is clean, only a burst of errors when the spiral track crosses over. the burned disc has a bunch of errors in the middle.

this burned disc worked partially but you can still see some errors.

i'm burning a disc right now on my old mid 2000's desktop. at 1x speed, it takes over 10 minutes to write just 63MB! i guess retrocomputing takes patience.

protip: disc package and label branding doesn't often match the actual manufacturer. for that you need the ATIP data. under linux, use "wodim -atip" to find out detailed info about the manufacturer and medium.

sorta hit a dead end but i have a few things to try moving forward:
1. swap out the buffer RAM chip (M41464-10)
2. hook up keyboard & mouse, boot WB from floppy, and try to view files (instead of booting from CD)
3. swap out LC8951 (error corrector and host interface)

current status: out of desk space.

hacked up a PS/2 to IR converter. and yes, that's an original PS/2 mouse. only one I had handy 🤪

the keyboard adapter was a huge pain. this is not a standard mini-DIN connector and I had to shave down the plastic tab to get it to fit!

i can get a directory listing of the files on the CD!

and I can even run the program manually. however it seems to freeze at this screen.

i'm starting to think the CDROM drive is fine and the issue is the developer CDTV ROMs in this thing. those are the two flash chips on this board. perhaps they need to be the official "release" versions to work properly.

see, every CDTV disc includes the file "CDTV. TM" which had to be licensed from Commodore (TM stands for trademark). perhaps it needs to be matched up with the CDTV ROM itself. 🤔

upflashed to 2.7. still the same problem with the CD-ROM. 🤔

the version of the CDTV extended ROM in the flash developer board is 2.0b1. this looks like a previously unknown beta version!

probably ought to test the RAM just in case

that's interesting, the DTEN# line on the CD-ROM drive isn't going low all the way.

the buffer on the drive side has a 470 ohm resistor in series. on the buffer side, the voltage goes to ground.

the other side (the input) is this 6525. basically it is a gpio chip. must be pulling up with about 5mA!

so I removed that 470 ohm resistor, and nothing changes! I can still access all the files on the CD, I just can't boot from it. 🤔

if I remove jp15, I just get the normal kickstart screen

logic analyzer time.

that pin (pin 13, PB3) is only ever set to be an output. so as strange as it may seem, this is a 30-year old bug. but i'm back to square one; this doesn't explain why it won't work.

back to the logic analyzer. this time I'll just probe the CD-ROM interface

this is a seek command. sector 0x000010, length of 0x0011 (17 sectors of 2048 bytes each).

the CDTV reads these sectors before freezing. (values are in hex)

i wrote a crappy python program to scrape the binary data out of the Saleae Logic csv dump. next step is to compare it with the iso file and look for any differences.

it matches perfectly. this CD-ROM drive is working.

let's try downgrading the kickstart ROM to 1.3, just for kicks

oh now it works! the welcome CD was just incompatible with the newer kickstart ROM.

time to stuff this all back together.

and now i can watch a tutorial on how to insert the welcome disc into a CD caddy. 🤔

the disc also contains important information on how 1s and 0s are transferred from the disc to a location off the screen to the right.

oh this is some nice pixel art.

OK.

there's a slideshow of some of the games available.

"ninja" 😂

they've even got "Unreal" but I suspect it's not the FPS

then there's the usual collection of shovelware

uhhh is he winking?

oh it's Barney the clearly not purple bear

voiced by Mr T. I pity the fool... who doesn't go to Fun School!

more Barney except this is a mashup of Pooh and Dr. Who

say what now? 🤔

it's a coffee table book for your CDTV.

would you believe i know Commodore paid $16K for this welcome CD to be produced? do you want to know how i know?

we'll, i'll tell you. a copy of the invoice IS ON THE CD ITSELF!

there's even a credits file. oddly enough i know some of these folks.

(insert joke here).

maybe "joke" refers to the file, "JOKE.ILBM" that i also found on the disc and doesn't seem to be used anywhere.

the CDTV also works as a CD player, and the UI is *glorious* -- it just doesn't get any better than this!