Akai S612 MD280 repair and restoration

[themilford]

I have two S612 units and two MD280 drives. One S612 seems to work mostly properly, but I'm sure it could use a once over and some new caps. One drive almost worked... got one sample to boot once. I found belts online and ordered them. The second s612 has some issues. No signal, even after replacing two blown fuses. Midi seems to trigger from panel LED. Second Drive had melted belt.

I was going to try to refurb these myself but I think I would prefer a clean bill of health from a pro that understands them. Any advice. My local repair place, (analog lab) has moved to the west coast and this my not be there specialty anyway. I'm in NYC area, happy to box them up and ship or drive up to an hour to get them 100%.

[madtheory]

You already replaced the fuse? Oops. These things have a PSU issue. If fuse blew and you replaced it, damage has been done to the main board. See hideawaystudios thread on the S612 MIDI animator, on this forum.

[themilford]

You already replaced the fuse? Oops. These things have a PSU issue. If fuse blew and you replaced it, damage has been done to the main board. See hideawaystudios thread on the S612 MIDI animator, on this forum.

Yeah, I read all that. I replaced the fuse with the same value. So, interestingly, the working one had a blown fuse and was still working... weird. Also the "working" fuse was wrapped in foil (gotta love folk that think they can "fix" stuff) but this was the functional unit. I replaced those with correct values as well and this unit seems to be working.

Isn't Hideaway in the UK? I would love to find a real expert on these units stateside. I would be happy to drive or box these up.

[themilford]

BTW: the thread you mention is over at Gearslutz.

[madtheory]

Ask the guys in Control, Brooklyn? Surely they know someone!

[themilford]

Ask the guys in Control, Brooklyn? Surely they know someone!

Thanks, gave them a call. $100 bench minimum, $120 per hour. No thanks. New York sucks for repairs. In the 'burbs and other cities these kinds of repairs are often much cheaper... and honestly I've found better quality work outside of NYC.

So, I think I'm gonna gamble with doing the work myself.

Already ordering Transistors, Regulators and capacitors for the power supply boards from Digikey. Ordered Belts from this place:

https://console5.com/store/akai-roland- ... -belt.html

Somebody replaced one of the slide Pots with a bunky one... anybody know if there is a modern equivalent?

[madtheory]

Ya should be fairly straightforward, the issues with these machines are well documented. Is there a service manual available? It's a pity no-one has yet figured out how to replace the MD-280 with an SD card reader. It's the Achilles heal of this otherwise attractive sampler. From what I've read, QD format is basically the same as cassette data storage, except the tape is a disc. It's pretty archaic! Have you tried contacting Hideaway Studios? He's a top class repair dude, clearly knows a lot about this specific machine, and is very enthusiastic about keeping these great old instruments alive.

[themilford]

Ya should be fairly straightforward, the issues with these machines are well documented. Is there a service manual available? It's a pity no-one has yet figured out how to replace the MD-280 with an SD card reader. It's the Achilles heal of this otherwise attractive sampler. From what I've read, QD format is basically the same as cassette data storage, except the tape is a disc. It's pretty archaic! Have you tried contacting Hideaway Studios? He's a top class repair dude, clearly knows a lot about this specific machine, and is very enthusiastic about keeping these great old instruments alive.

Yeah, I've got some minor electronic repair skills. This is a bit more complicated than my typical pedal or amplifier circuit. But refurbing the PSU should be easy. As long as that's all that's wrong. Interestingly, the AX-60 build around the same time has non of these PSU issues.

Mr. Hideaway has responded to me over on the other forum.

The MD280 most certainly needs to be emulated. It should be fairly straight forward, no? I would be willing to donate my extra MD280 and S612 if somebody want to tackle this.

[themilford]

It's a pity no-one has yet figured out how to replace the MD-280 with an SD card reader.

there's a bit of a discussion over there:
http://torlus.com/floppy/forum/viewtopi ... 0&start=30

[themilford]

So, I got both QD drives working. Belts from above place worked like a charm. Replaced belts and a quick swab of the heads and they load the only Akai Sound Library disk I have. No other adjustments were needed. The other discs (hand-labeled Roland disks) will intermittently load, but the samples sound glitchy and are only triggering monophonically. New transistors, regulators and caps for the power supplies in the samplers are on the way... One sampler seems to be working fine as is... but it may have quirks that I have yet to identify. I plan to overhaul all units either way.

I'm ordering some 13-pin DIN connectors and audio-quality (Mogami, 6 conductor plus shield) to make some Voice cables to use with my AX60. These will be way nicer, shorter and cheaper than the Roland or Kenwood CD remote cables.

[part12studios]

First of all as a fellow owner of one of these I wish you the best on bringing this back! It's a special little sampler that's for sure. It's worth saving even if it's a DIY situation!

Also just in case you didn't know, keep in mind that you can (with rom 1.1 or better) sysex dump samples to it making the QD drives less important, but I have one that works so I'm avoiding using sysex, but a buddy of mine who also has one uses sysex without trouble.

I wrote Arturia a fan email saying their next product needs to be a "SampleBrute" and that they need to seriously look at the S612's start / stop sliders as a must have feature that's missing from any other sampler I've ever seen, aside from software like ableton.

[HideawayStudio]

I have indeed worked on well over 30 S612s in the past year and only one of them has yet failed to return to life.

I have posted the weak points including equivalent parts for overhauling the 612s rather notorious power supply on the Gearslutz FPA module thread.

As well as my FPA Module for the 612, which is proving very popular, I spent a lot of time reverse engineering the QD drive system on the 612 last year.

I have kept relatively quiet about this till now because I didn't really want a deluge of enquiries about what I totally agree is the weakest aspect of the 612.

The QD is unusual and has its roots in Japanese game consoles very much of yesteryear. This disk system is not so well understood and is often mistaken for some sort of cut down/low cost variant on a more conventional Shugart compatible floppy disk system (ie. not like Amstrad's 3" floppy system which is exactly this).

Almost all floppy drives, even when they don't appear to be (eg. the floppy drive in the SY-77 with its non-standard ribbon connector) are Shugart compatible - this even includes the original 8" SA-800 series floppy drives on things like the Series II Fairlight. In fact this is where the name comes from. The superb Lotharek Rev.F HxC drive is a Shugart emulator - it is perfectly possible to connect almost any floppy drive to HxC and indeed I've hooked up a number of extremely rare 8" disk systems to HxC so I endorse that product with great enthusiasm.

The QD system on the other hand is so different to Shugart that a totally new firmware build would be required to make it work with HxC and the wiring to the drives is completely different (and, as its creator says, even the connectors are not so "standard" from one drive to another either). The reason for this is that the low level design is actually more akin to a radial tape drive than a floppy disk. There is no stepper motor - drive works by mechanically enscribing a single spiral of data rather like a record in one hit quite unlike a floppy drive which writes data in a series of concentric tracks and has a stepper motor to randomly seek for those tracks. So the drive has to load the entire memory contents in one shot - there is no concept of random access or a filesystem.

More bizarrely is that, after much careful cross comparison, it turns out that the entire drive system for the S612 has been lifted from a games console of the era even including rear panel edge connector pinout! The drive itself has been rather crudely rehoused in a 19" case but its the very same drive minus the support ROM which would normally be housed in the large edge connector housing (you can even see the space for the ROM on the pcb!!).

To prove this I have even put the two pcb sets side by side and you can see the parts and tracking are the same.

Yet more bizarrely again is that the drive is not hooked up to a Shugart style parallel interface but is in fact hanging off a high speed synchronous serial interface courtesy of a Z80 SIO chip housed on the drive interface inside the drive unit. If the drive was asynchronous serial it might have been quite easy to emulate but sadly not but, even then, would never be able to work any faster than the original data rate (mind you HxC is the same in this respect).

I spent a great deal of time with a deep memory logic analyser sifting through the data and reverse engineering it to the point I successfully determined the data structure for the front panel settings and the sample data itself. I even managed to extract audible sample data from the raw data via the logic analyser.

I passed this by David Cockerell last year who very kindly responded and he seemed to think it looked ok. In fact I suggested the data did not contain any error correction and at first he thought I might have made a mistake but later came back after reminding himself that this was the case on the 612..

So there you have the reason for clicks and pops on 612 floppy loads.. its because the system simply doesn't know if the data it has loaded is free of errors.

This is made much worse because the system is not very tolerant of head misalignment or variations in rotational speed so it is therefore possible to load and record on one machine, take your QD to another drive and it wont load at all or not very well...

I do indeed have a solution to all this but its tricky and will take some time to perfect. It involves some surprisingly hairy coding because the memory bus on the 612 is actually surprisingly busy (it may only be Z80 based but it has two DMA chips!!) and the timing is pretty critical with lots of stuff hanging off the bus.

[paul.boos]

Revisiting this thread, I want to thank everyone for sharing their experiences and information. I have a MD-280 that has died on me. Thanks fully I have 2 of them (and 2 S612s), but it cramps my style not having the second one running - imagine plugging in one MD-280 back and forth between 2 S612s. Yeah, you know what I mean - it thoroughly sucks and is unworkable.

So I'll see what I can pull out of this to revive it.