Announcement

Collapse
No announcement yet.

GEAR: Yamaha C1 Ultimate PC Sequencer

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • GEAR: Yamaha C1 Ultimate PC Sequencer

    The Yamaha C1 music computer is the daddy of MIDI sequencing from the early 90s..

    Released in 1989, it was a stupid amount of money, but had 8 MIDI OUT ports, SMPTE on-board, and ran Voyetra Sequencer+ software with a full 128 MIDI channels
    available.

    The machine is CGA, 10Mhz 80286, and came with twin floppies or a 20mb Hard drive.

    I have had 4 of them in my time. The first was a USA twin floppy, with a broken screen, my first purchase on eBay back in the 90s.
    It exploded one morning when it had 230v shoved into it. I had it booting from floppy and mounting a Zip100 disk. It worked. So what.

    The second one i found online in a GOODWILL in the USA. It went missing in shipping, and i got refunded.

    The most recent 2 came from the UK eBay. Both 20mb HDD versions.

    I have started working on one.

    the service manual is here - https://archive.org/details/MusicComputerC1 and here - https://www.lo-tech.co.uk/wiki/Lo-te...er_IDE_Adapter

    It's nice, just a little bit useless for some things. Parts list, yes, and layout, yes, and how to take it apart, yes!

    C1mobo.jpg

    So, right away You need to remove and replace the 9 metallic green 47uf/25v capacitors on the motherboard. They will all have leaked, and will smell of fish.
    It will not be easy getting them to come out, prepare for anger. I'll leave that to You to work out. Best of luck.

    Around each of these will be damage. You will likely be able to patch the broken traces on the top or underside of the motherboard, except for the ones near
    the expansion slot, which are pointless to repair as there are no compatible devices for this slot. So. Don't fret. Making all these tracks good again will be
    helped by the layout diagram in the service manual.

    C1leakycap.jpg

    I went ahead an removed some of the other caps - the 220uf etc., and they were still fine, so, your call on them.

    Now, to the issue that will kill your secret plans to revive one: The fuc*ing power supply.

    It's a Nichicon, 87P-50(E) ZSNK730HA. Nichicon used to make power supplies in the 1970s and 80s. They appear to have no record of these anywhere. Mine is
    fuc*ed. The fan does not come on, and there appears to be only about 150VAC floating about the primary section. I detest early switch mode power supplies, and
    i have no luck rebuilding them, apart form the one on my O.G. Arp 2083, which was a doozy.

    The service manual has a parts manifest for the PSU, but no diagram, no real details. No, this is best replaced with a known working alternative. Much less
    brain damage.

    We need to know what voltages to offer the machine.

    So, looking from the front of the machine, the white lead with 9 pins connects the PSU with the motherboard. All the devices in the system get their power via
    the motherboard.
    From left to right, pin 9 to pin 1:
    COM +12V COM -24V -12V COM COM +5V +5V









    Yes, you read that right. -24v on pin 6! We know this because that pin is fed by the output pin of a Panasonic AN79M24F Series Regulator. This is a -24V
    regulator, capable of pushing about 500ma. This leads to the riser that the screen/top case connects to, and is likely used to power the invertor that drives
    the LCD screen backlight. elsewhere in the PSU we find the -12v version of this panasonic part, and this traces to the -12 pin on the bus, and on to a
    regulator on the far left of the board that makes -9v. We can also confirm +12v as it's used to power the fan in the PSU. +5v can be traced to the 80287 slot,
    and the +5v pin there. So. All voltages are identified

    You can go ahead and try to find an off-the-shelf PSU that will do 5,12,-12 and -24v from house voltage, and if you can find one at all/cheap, and it will fit in the
    space vacated by the original one, then go for it.

    Meanwhile in the real world, there is nothing of the sort available that i can find in a single unit. You need to treat the -24v as it's own problem.

    We know from the spec sheets of the -12v and -24 Regulators in the stock PSU that both lines are rated for 500ma, so, a +/-5 and +/-12 PSU like a Mean Well
    RPT-60B, is about 35eu new, and it will provide the required 500ma on the -12v line, with 4.4a on the +5v and 2.2a on the +12v line. It's also small enough to
    fit in the bay, with about half the space left free, while avoiding the mains input and power switch stuff.

    Making -24v can be done 2 ways. Add in a second PSU just doing the 24v, and reverse the polarity on the output - THIS ONE looks nice - or, You can just 'buck convert' from the 12/5v PSU, with a "TRACOPOWER TEN 40E DC-DC Converter, ±24V dc/ 833mA Output, 9 → 18 V dc Input, 40W" DC-DC convertor, Mfr. Part No.:
    TEN 40-1225E. It's not cheap - about 60euro, but i have used these in RF-sensitive equipment, and they are invisible when correctly deployed. This will accept 12v from Your basic PSU and bump it up to +/-24v at up to 866ma. You need to pay attention to the application notes for this unit,
    as it needs a little work to make it interference-proof: http://www.tracopower.com/overview/ten40e - basically a couple of caps and a dual inductor need to be used to avoid it being a
    source of random buzzing noises in your studio. No big deal. The Dual Inductor TCK-177 they spec is a touch pricey, and always in short supply, but you can try an alternative
    with almost the same ratings: The KEMET 500 μH 15 A Common Mode Choke 8mΩ Mfr. Part No.:
    SC-15-05J - this is basically a dual coil inductor, and is very close to the one mentioned by TRACO in their notes, and available in small numbers.

    You can of coarse just use The TEN 40E straight, with no noise suppression if that suits You. I would not though. If You have come this far, do it right. These things (especially the many you will find on Amazon) are 'square wave PWM choppers' and generate nasty electrical noise while doing their jobs. The less You pay, the more noise/buzz/crackle You will endure, and the more risk of burning your shack down.

    So, total price for a NEW power supply made this way is about 90euro, less, if like me, you had a +/-5v,+/-12v PSU lying about. I have a few actually, as
    my Emulator IV was eating them for a while, until i worked out it was the Molex connectors that sucked, and the Flash RAM stick needed cleaning and
    re-seating.. DOH!

    Also, You can try just ignoring the -24v if You intend using the C1 with an external display. The output is CGA, 640. You can find a convertor to make this VGA
    here: https://www.aliexpress.com/item/33059176013.html about 40euro landed. Just set the dipswitches at the rear to enable the external display and work away.

    So, this is a W.I.P. for me.

    Caps are done, tracks all repaired - next is power supply build - i have the Basic 5/12/-12 unit, waiting for the Traco +/-24v device, then We can see if I am wasting my time on this unit.








    Last edited by playthatbeat; Wed 17-07-2024, 9:02 PM.
    jUst plAythAtbEAt

  • #2
    While waiting for bits to try my Traco/Mean Well PSU, I decided to look into the inverter - the backlight driver for the screen - as it shows being capacitor heavy in the service manual.

    invert.jpg

    You will be delighted to hear all the caps in this tested out as reasonable. One, a 100uF i think, was testing in the Pf ranges on the board, so i pulled it to check, and it was fine. All the others were testing as OK.

    Getting at the inverter is not easy. It's a minefield of very thin wire runs, jagged shielding and screws into plastic. REALLY leave it alone unless your screen backlight is flickering or dead.

    You need to expect this area of the machine to make some noise, a little buzzing here is OK.
    jUst plAythAtbEAt

    Comment


    • #3
      Power supply is good, works fine.

      When testing all the voltages before connecting to the motherboard, i did notice the FAN would pull the +12v line down to 9v, but this is the nature of Switchmode PSUs.

      So, We are running a MEAN WELL RPT-60B for the 5v, -12v and +12v, and the TRACO TEN40E fro the -24v, driven by the 12v of the Meanwell. The COM of the -24v output pair can/is added into the Negative of the power loom to the motherboard, and works well.

      C1-PSU.jpg
      jUst plAythAtbEAt

      Comment


      • #4
        On powering up, all is passing the bios tests, except the Hard disk, which is (as expected) fuc*ed. It spins up, nice & noisy (RLL), but will not mount, giving errors to the Bios. The setting for the drive is TYPE 2 in the bios, and could possibly be unformatted if I am reading the user manual correctly? There was a bit of a fishy stank for the first few minutes of powering up, akin to the stank off those green electrolytics i replaced. I suspect the hard drive itself has capacitor issues, which i may be able to address.

        The Floppy drive is a 720k unit, and works fine. Swapping it out with a 1.44MB unit is not looking possible, even though the Bios claims to support such a drive. Altering the floppy setting in the bios gives a CONFIG ERROR on boot. The other issue is the stock drive has it's connectors on opposite sides from every 1.44MB drive i own, meaning a different drive would have to be mounted upside-down, or a new floppy lead deployed to reach. The current lead is a twin-port one, i guess so the 2-floppy machine can be a thing.

        So, is it GOTEK time? or time for one of these: https://texelec.com/product/lo-tech-...r-ide-adapter/

        I will shortly have both on the bench, so let's see.

        Meanwhile, everything works like 1991 baby!! Look at how bright and crisp this LCD Panel isn't:
        c1-qb.jpg
        jUst plAythAtbEAt

        Comment


        • #5
          Hard drive is a simple unit with a single board attached by 4 hex bolts, and connected by a ribbon cable and 2 multipin connectors.

          c1hdd.jpg

          It does indeed have caps that have the fish-stank, and replacing them is no big deal. You should expect to do some serious cleaning, and some clever positioning of the caps if you opt to avoid replacing them with the same exact type.. You need to get them in the available space when the drive is rebuilt:

          c1chddcapped.jpg

          After capping, the drive spins up on first powering the C1, then does the usual fail nonsense. BUT, the LED for the drive does run GREEN then RED before failing, whereas before, it did not.

          The drive is not recognised still. Fdisk fails, blah blah etc.

          SO, maybe it's the small one by C55 that i did not change? I don't really care at this stage, it's not that important. I had a hankering to see what was on it, but the user manual goes into depth on how to use FDISK and so on to prepare it, so i think it shipped as empty.
          jUst plAythAtbEAt

          Comment


          • #6
            The https://www.lo-tech.co.uk/wiki/Lo-te...er_IDE_Adapter arrived, and as You can see, it will not sit properly with a lead attached:

            oopsboard.jpg

            The trick here is to remove the top plastic clasp that folds the lead back on itself, then the board will sit flush.

            I use an IDE extender lead to reach into the drive bay vacated by the old hard disk https://www.ebay.ie/itm/255118593431 and into it i mounted an industrial IDE SSD device, found on Aliexpress: https://www.aliexpress.com/w/wholesa...l-IDE-ssd.html - this needs 5v to run, which is available from the spare floppy power riser on the mobo, or from my PSU directly.

            ssd.jpg

            This is guaranteed to be seen correctly by the new IDE board, and FDISK in DOS 3.3, and of coarse will format to 2gb partitions in >= Dos 4.x

            Once this is all in place, the usual DOS install routine from floppy, FDISK etc. is needed, or, just use your usual DOS .img and prepare the disk in another machine then transplant it.
            jUst plAythAtbEAt

            Comment


            • #7
              When setting up the C1 to run Voyetra software, there is a GOTCHA.. You will find the software will not start if you load Dos HIGH. This would be a default in the config.sys for Dos 4 onwards. I have no idea why this is an issue, but it is. If DOS is loaded High, the software locks up when auto-setting the resolution. RESOLUTION is not about screen size, it's the milliseconds per cycle setting to ensure best sync, and for most fast processors, is 1. For this 286/10 it's 3. For an 8088 it's 6, with a slowest setting of 10. You can force each and every permutation as a switch in the SEQ batch file, and the best you can hope for is a DIVIDE BY ZERO error. Loading Dos HIGH fuc*s with the timing and Seq+ will not run.

              MIDITEST would also lock up.

              I learned more on this by trying the demo software that came with the C1. The Demo "C1" version of Voyetra would lock up also. BUT, the "64trackPC" demo sequencer would not only run, but i could stream MIDI from each of the 8 ports. Sequencer Plus _will_ run with no SAPI/VAPI loaded, so, it is entirely an issue with how the C1 driver interacts with dos and memory. This driver was written by Yamaha, and was shipped for Dos 3.3 - a version of Dos that did not include the ability to load dos into a high memory block, so was never tested.​

              I have yet to test with Dos 6.22 - so far i have been using software that can be installed from 720k Floppy.

              SO, it all works. Loads fine, and is quite groovy on my IBM 5153 Monitor.

              286-seqplus.jpg


              jUst plAythAtbEAt

              Comment


              • #8
                On to the second unit now..

                As You can see, it's in slightly better condition, but a bit more dusty:

                c1-2.jpg

                There appears to be much less damage from leaking caps, but the places where leaks happened, it spread:

                leaks-2.jpg

                After replacing all the fishy-green 47uf caps, and making sure all the others were within reasonable value ballparks, only 1 spot needed a bodge wire: next to the riser for the monitor/top part of the case a via was not working thru' the board. It traced back to a pin on the riser socket, so i jumped a wire from there to the underside of the board.

                Maybe there is more damage i cannot see, but any places with dark traces i removed the mask with a fibreglass pen, and tested for continuity successfully. We will see.

                So, next i'll do the caps on the hard disk circuit board, and the inverter for the screen.

                Not sure i care about either, but if they work, it would be nice.

                I tested the PSU, and it's fuc*ed. So, the smart money here is to just get the 12, -12 and 5v running, and use my external display. Then go with a dual-floppy build, using a Gotek alongside the native drive. Maybe put it in a PC case, including a RGB to HDMI convertor! I like that idea... It's cheaper too.
                jUst plAythAtbEAt

                Comment

                Working...
                X