kgallen

Well with an eBay-special voltage inverter (17V in to -24V out, -30V would be better as @NGY says) the display and main processor are alive! However it won’t read discs - me thinks this OP looks suspiciously like it’s missing at least one important bit... Next question is do I fork out another 45 quid for a KMS-190A OP or do I declare this project-for-fun null and void?...

Welcome back! Even with the mighty knowledge of @NGY we’re struggling with a few jobs, so get your sleeves rolled up!

Alex. If it makes you feel any better, a year or so ago I knew nothing about the insides of a minidisc machine. I’m certainly no expert now and have nothing of the experience of people like @NGY. But through the help and advice of good people on this forum including @sfbp it’s possible to learn lots of the basics and where to look. If nothing else to learn ones own limits and the parts not to fiddle with! But it does come down the the owner learning and the history on this forum is a great place to do some of that. At this point I would usually say we’ll get your machine sorted one way or another but I’m not sure we’ve have the successes recently we hoped for! Keep at it!

My bad, I'm reading the topic title that says 780 but we've moved over to a 770 mid-thread.

If it's some variant of MDM-7 then it should match and probably work. My post on my E10 evening of swinging with a 480 and 440 drive is documented below if you have the time to read my drivel. If I remember correctly, one worked fine and the other sort of worked, so there could be some subtleties that mean only some variants are fully compatible with others. Then again I can't recall if they both worked flawlessly in their home machines (both 440 and 480 bought tatty for spares). Agree with @M1JWR that a 480 should be relatively easy to come by on eBay and at a decent price... although we've been advocating such a move a few times around here recently, so the 480's are probably going up in price... Kevin

OP = optical pickup (ie the laser sled assembly). You replaced the whole drive. Knowing and using the correct terminology is very important otherwise we can be at cross purposes. At this end we’re working blind so it’s important we are talking about the same components.

Maybe I missed it. I would add that motors and switches can be checked with a DMM without desoldering from the BD. Motors are driven from H bridge drivers so the motor is not in parallel with any low impedance and they are single winding motors not steppers. Hence DMM across the motor contacts should measure a small number of ohms (don’t know exact value, from single digits over about 4 to a few 10s of). Switches on the BD just pull to 0V against a pull up resistor so again a DMM across them should go from open circuit to very low resistance. Talking here for MDM5 and MDM7 but other drives are likely to be similar.

I’ll give a hand: Follow NGYs advice very carefully. If you want other ideas then look back through this forum over the past few months. The forum has been very active with great MD people with machine issues that are not so dissimilar. Part of solving issues with machines is the owner needs to build up some knowledge about the machines themselves and the approach to take trying to diagnose the issues. Only one person is sitting in front of that machine and that is the owner. Those contributing on this forum are trying to diagnose issues remotely and are totally dependent on the knowledge and ability of the person sat in front of the hardware. If you can replace an OP in 5 minutes then your abilities are well beyond any of us here.

All fair points well made! (But I bet you can find a little corner somewhere... :-D )

You're asking the wrong folk here - the answer is, "You can never have too many minidisc machines". From another pristine MD-350 owner (amongst quite a few more machines now it would seem...)

[I did resist my pedantic tenancies to correct, but we all usually know when people say silicon (a shiny metallic semiconductor and the basis of my career!) when in the context they mean some sort of silicone (a compound of some other 'stuff', including silicon probably, often used to seal one's bath tub!). One missing letter in a post of thoroughly good stuff is perfectly acceptable! :-D ]

Spindle motor is direct drive and is under the centre on the MD. The spindle motor is the only one that is spinning when playing a disc but there isn’t really anything you can get at to lubricate there. Edit: Top right is sled as NGY says, not load/eject as I initially said.

I've only recently seen how this works and it was on a portable (my N510...). However it's so simple it's probably the same on the decks. It's just a folded point of metal that engages the slot in the case and then it's effectively the case that slides and the cover "stays where it is". It's a relative velocity thing - the slider stays still and the rest of the case moves away from it - rather than the case staying still and the slider moving away. Cheeky and cunning at the same time?

Just get EM-30L. The right stuff, not just any stuff. Also available on eBay as above. This is what I bought, £3.99: https://www.ebay.co.uk/itm/Dow-Corning-Molykote-EM-30L-Synthetic-Grease-for-Audio-Office-Plastic-Gears/373078746082?hash=item56dd39e3e2:g:JdIAAOSwBQ1eNyLH

Have you had a look in the Downloads section? (Tab at the top of this page) I have no clue - but is this something different to SonicStage? There is some stuff called M-Crew in Downloads too, it that it? Sorry... Stephen will be here is a minute to give you the proper answer. Poooof... as if by magic...

There is a load-in-detect switch. SM p55 grid B8. I'd want to know that was ok first. The motor is next to it on the layout and comes straight out to a connector, so a continuity check should be feasible - the motor winding should be a few ohms. But we're getting ahead of ourselves with this one. Look for simple explanations first.

Can you get a disc into it (without forcing it!)? With one in can you play it? Daft question possibly, but you're talking about the eject motor. (There is a spindle motor and a sled motor too.) Kevin

(Off topic - I was totally amazed to find a standard remote fits and works in the NF610, which has some weird shaped RM bit of the combined 3.5mm jack/RM contacts for the radio remote. Clever them Japanese folk.)

I don't know. But I would agree that 9 times out of 10 it will be a silly/simple fault. Need a bit more info about the ghost that's given up. Usual stuff: what works, what doesn't, what display/LEDs, what noises.

Ha! We'll be 'round your house with pitch forks if you talk like that around here! :-D

Indeed, what I meant was "the information the main CPU needs to use the BD board is contained within the EEPROM", which is what allows us to plug-and-play drives. i.e. we don't need to go in and change and settings or reconfigure the main board when we transplant in a drive from another machine. I don't have a memory map of what is in the EEPROM, I just know we can "plug-and-play" - or if nothing else we seem to be able to do this without damage! Certainly the main CPU reads this EEPROM over I2C early on in boot (I've seen this on my protocol 'scope on my forever-faulty E10). @NGY your information and experience is invaluable, reliable and well-founded. Please "split hairs" (indeed I want you to) whenever needed (at least on my posts!!!) - this is a learning experience for me! :-)

Done. Thank you!!! :-)

Mmmm, probably unlikely. The MD unit doesn't use a "standard" interface like IDE or similar. You'd probably need to design a circuit (even a small FPGA) to interface something like an SPDIF serial stream into the SD card interface. Not beyond the wit of man at all, but not trivial. The other option would be to use something like a Raspberry Pi. If you are into electronics you could take some tips from circuits for "SCMS copy killer" for interpreting the SPDIF stream. Although of course you'd need to be able to do the reverse too - read your audio data from the SD card and create an SPDIF stream. This would of course be a fully proprietary solution though - you could only read and write your SD cards on this machine! We're not taking wav files here, although using a Pi might give you more processing options to consider that! Kevin

I've got a 520 and a 530 (amonst a lot of others!). The 520 was my first MD "baby" (receipt attached, oops, sorry it's so big!). The 530 was purchased a couple of years back from eBay with the aim of using MD again at my AmDram society (which, due to the 530 issue, got me into Tascam MD-350, then Tascam MD-CD1, then Sony MDS-E12 and E10... which then got me into 440 and 480... which then got me into... the rest of the list on my profile!!!). Excellent! As @NGY says, the BD board (EEPROM) holds this data - along with (I believe, possibly disputed) - the Iop settings for the laser. This is why you can swap drives between machines and the main PCB CPU knows how to configure the BD.

Hi chaps, Thank you both for your quick responses. Thanks @blixabloxa for the manual link. I do have the SM from Elektrotanya, but I will compare the one you provided as often there are several versions in circulation with different information or quality of pictures etc. So thanks! Schematics would be the key! @NGY thanks for your insightful investigation into the VFD, much appreciated! My MD-801R was bought "spares-probably-not-repairs" (I added that last bit!) just to have a play about with. It has been used as a donor deck to repair another (presumably), so is missing some parts, like this DC-DC converter (in general it's not in too bad shape). As we've seen, there are no schematics although at least a parts list which states U503 as a DC-DC. However there are no other specs or pinouts. Through tracing the PCB, I've worked out the pinout (for anyone that cares, assume you're looking down at a DIP8, then pin1=out, pin4=in, pin8=0V). The input is from the raw rectified/smoothed DC supply and I measured at 16.7V. The output of the DC-DC has a smoothing cap but it's in reverse polarity (cap+ to 0V rail, cap- to DC-DC output), hence concluding the output was probably negative. I found a Facebook repair post on this component. Not many details but one photo was annotated with "29V". Hence my two proposals of 17V and 30V and the likelyhood these supplies were negative with respect to the 0V rail. I've ordered a range of small DC-DC modules - both Boost types (thinking +17V -> +30V) and also some Buck-Boost inverter modules, so I can do both +17V to -24V and +17V to -17V (at least). So the info on brightness for -15V through -30V, and the datasheet picture you found is much appreciated. I did not want to blow up the VFD on the first attempt! I suspect this machine will still be a little poorly, but getting the VFD working will be a step forward in diagnosing the next fault. At the moment it will accept a disc, but does not spin it up and hence not read the TOC. So once the VFD is working I can take a look at the drive behaviour. Onwards, fellow MD-ers! Cheers, Kevin