kgallen

It's not a dumb question at all, I need to get my head around that too, it's complex. Separately: Teasing apart more info from the circuit description: On the "block" of memory, our FSM "state" is the top address bits. The SR (SPDIF data) is the bottom 8 bits, so SPDIF data values move us around the least-significant locations within a 256-byte block. Our state machine states are the upper 7 bits of address, so a movement in the state machine hops us around between 256-byte blocks. So the "detail" within a 256-byte block will be a "response" to a moving low-level SPDIF bit pattern, and the FSM will "jump" us to another state in the machine by moving us to another 256-bytes block. This probably makes little sense, but as we start to get the hang of how this machine "interprets" the SPDIF stream, it might help! (Maybe...!)

Ignore the wiring twist between the ROM (IC8) and the register (IC9) - I can just make out the address lines are brought back into numeric sequence to the left of IC9. Also note from the information supplied by @zedstarr above (and evident from the schematic had I looked) is the data presented to the shift register (IC7) will be in the bi-phase format as per the SPDIF on the coaxial or TOSLINK line. I need to check what format is used, but it may be Manchester Encoding which is a mechanism to convey a clock (timing) signal along with a data sequence (and to avoid a DC voltage offset accumulating on a long capacitive line).

OK all, I'll take a look, but it won't be a quick job! For starters I'm not currently familiar with the SPDIF frame structure which we'll need to understand to work out where this machine is trying to take us. Seems I left some links in an earlier post, so my chickens have come home to roost and it seems I'm gonna have to read them! I'm not sure where we're going with this - for me the endgame would be to draw out the FSM states/transitions. If anyone is building this then the bin file provided can be used to programme an EPROM (given the required equipment!). If you want to have a try at reverse engineering this machine, this is the bit of the schematic that is needed along with the binary file provided above. Use a utility like this to convert the bin file into a more readable HEX dump. (Above from here) SPDIF comes into the shift register IC7 top right. This shifts in the serial SPDIF and presents the most recent 8 bits to the ROM (IC8) as address lines A0-A7 (A0 being the newest SPDIF bit). The 8-bit register bank, IC9, is the FSM "current state" and the ROM contents are the "next state logic" that decodes the "next state" based on the inputs of the last 8 bits of SPDIF presented on A0-A7 and the "current state" presented on A8-A14. For some reason, maybe PCB layout or maybe decode convenience, bits 3,4,6,7 are transposed which means we need to keep this in mind when working out the decode. There may turn out to be a good reason for this, but I'm coming cold to this so I don't know the reason, if any, yet. There are 7 bits of "state". This means we have at most 2**7=128 states in our FSM - a lot to decode but I guess most of them won't do anything except move to the next state. In IC9 the 8th register is just registering the SPDIF output (top left) and you can see this comes from the ROM D0. This means for all but 2 bits of the SPDIF stream, bit D0 in the ROM will be the same binary value as the SPDIF input on A0, so D0 of pairs of addresses will be 0 (even addresses, A0=0) or 1 (odd addresses, A0=1). This machine has to find and flip two bits: the COPY bit and a PARITY bit (so I understand). This means in one specific ROM location you will see D0 be the opposite to what we expect from above. There will be one other location that has the same "flip" for the parity bit. So let's look first for addresses where D0 is flipped to the background pattern. These should correspond to the two FSM states that fix our COPY and PARITY bits... Some of the text is hard to read above, but all 3 devices are off-the shelf from many manufacturers, so if you need to, consult the datasheets, for example: IC7 74xx164 IC8 27C512 EPROM IC9 74xx574 By the way, don't worry about addresses 0x8000-0xFFFF in the bin file - address A15 is tied off to 0 in the design (above), so we can only ever address the bottom 32KB of the ROM, 0x0000-0x7FFF. In the bin file you can see that the top 32KB, 0x8000-0xFFFF are all 0x00 - ignore it all. This design could have used a 27C256 32KB EPROM rather than the 64KB 27C512 shown above - actually the pinouts are compatible, so if you're building you could use a 27C256 or a 27C512...

EE Block Engineering. Now we’re talking! Did you ever go ‘over the top’?! Who am I kidding, of course you did! :-D

There should be one "juicy" section that finds then inverts the COPY bit (and another bit that inverts the parity to keep it consistent). The bulk of the rest of the values will be background "fill" that does "output bit=input bit, clock next bit". If you have a hex dump, maybe you could share small parts of any interesting sections here? Might be of interest to the earlier poster where I was trying to describe how such ROM-based FSMs work. Echo the thanks to @zedstarr (and forward posthumous greetings from GPT Beeston to GPT Liverpool :-D )

Other option, not a Tascam one but a "programmed" substitute... https://www.remote-control-world.eu/rc-for-audio-hifi-tascam-c-12_715/tascam-rm-mc1-replacement-remote-control-p-7084?currency=GBP&gclid=Cj0KCQiAvbiBBhD-ARIsAGM48bwu4INh5l_JYKIlImKRhpv8wNGfPPoGqw1bHr3oqPNHpHp0jcnrkk0aAmmuEALw_wcB

I'm looking for a Tascam RC-MC1 at the moment... (for Tascam MD-CD1). Anyone know if the RC-5 would work with this machine? (I guess there is a good chance it will work with the MD section as the IR manufacturer code will be right...) https://www.ebay.co.uk/itm/Tascam-RC-5-Mini-Disc-Remote-Control-Tascam-Original/363226779505?hash=item549200cf71:g:RVQAAOSwbwFeySdn

I doubt anyone is looking, but there is a Tascam RC-8 listed on eBay UK at the moment (at a moderately healthy price): https://www.ebay.co.uk/itm/Tascam-RC-8-Wired-Remote-Control-RC-Unit-for-MiniDisc/133446843259?hash=item1f120d3b7b:g:xzwAAOSwO5BeXtLn

For other readers who are wondering what we’re waffling in about, here is a Wikipedia article talking about one phenomena due to a manufacturing issue: CD bronzing A few months back I purchased a second hand Compact Disc that seems to exhibit the above. It wouldn’t read. It was an 80’s CD from the period and ‘Made in UK by PDO’ so quite likely from the cited Philips/DuPont manufacturing plant. I’ve not seen this particular phenomenon on an MD (I’ve a sample size of 2 for MD-CD though!).

At last. I was getting bored of cheapo-"VU"-meters videos. Back to good 'ole MD :-)

We're largely not interested in the top side of the disc, so long as it's not in a condition that would damage the overwrite head. All of the "magic" is the inner layers of the disc, sandwiched between polycarbonate layers for protection. The optical transparency of the underside so the laser can "see" the MO and reflective layers is key to reading the disc. During recording, the OWH creates a (relatively wide) magnetic field that permeates to the MO layer whilst the laser spot-heats to the Curie point (185degC for the alloy used in MD) from the underside to record the single binary digit at that disc location. Rinse and repeat. Here is a diagram of the "disc sandwich" from the Minidisc Technical Primer from minidisc.org : Here's the statement on the OWH contact for all you "lube fan-boys":

Recording spot-heats the disc, so this probably drives off any moisture that could cause oxidation of the disc surface. The discs you experienced this with, were they still in their intact wrappers prior to the use you describe? I've only seen this (or similar) on one disc - a TDK MXR that I'd had for many years (well since ~1999). On one part of the disc it had what looked like small rust spots on it. It would not read.

Sounds like the internal power supply to me if the whole system freezes, rather than just an audio issue. Possibly the power supply going into shutdown through a heating issue or a component that drifts out of tolerance with heat. Could be just one of the rails, possibly a controller logic rail (say +5V) if there are signs that "something" is still on but the system is otherwise non-functional. The popping might be due to the rail rising again briefly before shutting down again. Probably not a user repair, but it would be disappointing if a general electronics service technician wasn't prepared to at least have a look. Diagnosis might be tricky but I suspect the fault once found would be relatively easy to fix. Being able to offer this Service Manual, that does at least have the schematics, might help (and possibly around the circuit of Q101): Service Manual: https://elektrotanya.com/technics_se-hd501.pdf/download.html Needs more diagnostic work to narrow down the problem area. It looks like a modular system, so if you unplug various sections and test, what can you ascertain about when the fault shows and when it doesn't? (Accepting with the CD disconnected you can't play a CD...)

Writing the titles is the same process as writing the audio data. On the basis of that argument, the best way to "save your machine" is to never record an MD. The audio data on an MD is around 200 megabytes (say 200,000,000 bytes). Any titles will be at most a few hundred bytes (say 200 bytes). Go figure! Maybe this tale comes from the AMS knob "wearing out" selecting each of the letters. From experience, using that method is more wearing on the human performing the labelling process than the machine! Glad your deck is back to life, heartening to hear!

Don't know about the internals of this machine, but sounds like a weak eject belt if it has such a thing. I would try and give it some assistance from outside when trying to eject, maybe some tweezers or fine-nosed pliers. Not to pull out the disc, but to just try and help the mechanism when it tries to eject. If it's stuck halfway then you might have to help it back in fully then try the eject again. Otherwise it's a similar process with the lid off - usual warning about mains electricity. Then it's locating and fitting a new belt it it is such in this machine. To be continued... SM is here: https://www.manualslib.com/download/754470/Onkyo-Md-105.html Parts lists page -7- have "loading gear", but I don't see a mention of a belt yet...

So the PCBs for my little TOSLINK splitter project arrived this morning and I've built a couple up and they are working a treat. One of these is for me and the other for @sfbp to replace his broken one. Hopefully this design is a little more "Stephen proof" :-P . I have a few spare PCBs (unpopulated), so if anyone in the UK wants one, then PM me some details and I can pop you one in the post with the schematic. You'll have to source your own components and do your own soldering, so please don't ask if you're not up to this - giving stuff away for free does imply the recipient won't waste such gifts at the expense of other who have genuine need. If there is a lot of interest I will allocate in preference to regular/active contributors on this Forum.

:-( Hope this doesn’t mean an end with minidisc for you...

Great insight guys! A converter it is! :-)

@NGY no problem! I’m 0 for 2 today :-( but in good company of the truly knowledgable! ;-)

Interesting question. Portables of course have to work at any angle. Whilst the mechanicals of a deck are different and by default would expect to be horizontal I would expect the tight tolerances and low mass of the MD drive parts would be fine. I don’t think I’d have any worries about playback. Record would be a minor concern but the OWH is such a tiny lightweight part I doubt gravity would be an issue!

Ok I did some research. US is 120V +/-6% -> 112.8V to 127.2V Japan is 100V +/-10% -> 90V to 110V So US equipment needs to work down to 112.8V and Japanese up to 110V. Internally, one logic supply rail is 5V. The unregulated supply for this would be 8V (minimum). In the US this would require a 112/8=14:1 transformer. For Japan a 90/8=11:1 So if we stick US 127V into a Japanese 11:1 transformer we would get 11.5V out. This 3.5V difference at the regulator input will result in slightly more power dissipation from the linear regulator. At the currents used by this equipment I would expect this to be easily accommodated in the thermal design. My MDS-E12 has a power select switch 100V or 220V. I think the intention here is it can be used on ~100V supplies (US/Japan) and ~220V (Europe/Asia/Australasia) supplies quite happily. Comments?

I bow to NGY if he thinks the below is wrong or others in the local area that know the specs. I would compare the power network operators voltage specification for the US versus that of Japan. You may find that the US 110V +/- % spec versus the Japanese 100V +/- % spec overlap such that you can use the product as-is on the US supply without issue. For example here in the UK our supply was nominally 240V ac, but in order to harmonise with the European supply of 230V ac, the spec of the UK supply was changed. No one changed any equipment either in the power distribution network or in their homes. This was a paper exercise only. The point being that equipment built for the European market is perfectly at home in the UK, or even Australia with its 240V supply. This equipment generally uses a transformer. The result of the step-down means that the input being 110 or 100 will result in a much smaller change than 10V on the secondary. Find the specs, do the maths. Any other reason the two power supply scenarios differ that affects the conclusion? Supply frequency is not an issue. US is 60Hz but the spec label on the unit shown above allows 50Hz and 60Hz.

That's true from my failed searches! Yellow-ringed RCA sockets you can get. I've not found an orange one anywhere - except on that stacked TOSLINK/Coax part I listed above from CPC.

I'm on the case. Might have a little gift for you in a few weeks... (months...!)

MDS-JE480 I'd expect, it's a sub-equiped 980! Never done it but my assessment would be this is not a trivial job - mostly down to the desoldering required to remove the old one first. No doubt some have done it but to do it you'd need a donor drive and I'd just fit that one instead.