Chatting with some Drives by DBMoore «» 44 «» 44 «» 44 «» 44 «» 44 «» 44 «» 44 «» 44 «»  I used to figure myself as one of the inadequates in the computer crowd, with only a pair of disk-drives and a lonely 1Meg of ram. The situation has now changed, with the addition of a Scram & Seagate... And none too soon, as poor old DF0: collapsed in a quivvering mess of lost identity shortly after fitting the upgrades....along with my real time clock, and my 14Mhz accel. hack......a small price to pay for such luxuries. [Just a small side-note, I actually got DF0: up and running again some weeks ago, it's problem was confined to the front pair of microswitches going insane, and I also got the accelerator to play the game too, by installing the logic described a la MD_18....... ....must have been the 30cm of wire to the switch, I reckon...., but the real time clock STILL eludes me, rotten thing! Anyone else had a problem like this, after fitting a Scram??] I suppose it stands as real testiment to how 'crippling' it is running without a h/drive and xtra-ram, that I really didn't miss my 3.5" drive, and rarely used it's 5.25" companion with my new setup......this happens. Eventually though, you know you're going to need a 3.5" diskydrive, and the ever-present pile of neglected games boxes reminds you of this. So what to do? Secondhand xternl Amiga 3.5 drives are still fetching around $70 in the Trading-Post and so-on, new ones being somewhat more expensive again.....[though I might add, you can get some fairly trick ones nowdays, that'll put a couple of Meg on a floppy....still expensive though.] So, back to MD_19, 22 & 24 we go,[or was it 26??] and the circuit mod to hook-up an old 720k ibEm d/drive to the Amiga, with a few dollars worth of TTL. [I should've looked at my old drive closer, but I'd already pronounced it dead.....retrospect!!] The "Chatfield Interface" will talk to anything.. electric can-openers, fridges, hair-dryers etc....which is just as well, because as near as I can figure it, this is where you'll probably find the remaining mass of the disk-drive units mentioned in those earlier Megadiscs. Those drives have obviously long since found a friendly smelter, and had their constituents recycled into something else .....like perhaps your pop.up toaster. Unfortunately, toasters have a different format to Amiga 3.5" disks...so do can-openers...fridges.... I simply couldn't find any of the listed drives, even after working out just where to look for them. Where? Well, at a place that specializes in the recycling of electronics/computer h'ware for the precious metal content. He had 720k drives....boy did he have some drives, shelves of them....but none of the models mentioned in the Megadiscs. [it was almost like some modern techo museum for old, extinct computer gear....tonnes of it....literally!!!] I reckoned with so many to choose from, it'd be reasonable to expect at least ?ONE? of them to be suitable....maybe. I told the fellow what I was up to, and we struck a deal; 5 x 720k, 3.5" drives for $30....and I was welcome to exchange one's that wouldn't Amiga, for others that perhaps might. Bargain! So I was off home with my boxful of digital dinosaurs, with grandiose plans of nutting out how to get them to work...if one could....with Meegee. I figured I could let everyone know about my successes, and build a more extensive list of possible candidates for DFx: work. This is absurdly cheap for an xtra d/drive....$6 for the drive, maybe $3 for the interface, a couple of bucks for the DB-23 & cable. Another drive for under $20......this has gotta be the way to go. Of course, I've lost some sanity along the way. If you think the drives themselves are hard to find, try and get any technical docs. on them! It's like the Loch Ness monster....you'd like to believe it exists, but get any hard proof that it ever did? You must be kidding!! I got very strange looks from almost everyone.... So, you get left with mindless hours, poking around unfamiliar boards with your logic-scope, trying to fathom the workings [or not!], of controller-boards with obscure little board settings...sometimes jumpers, othertimes, just little unmarked solder-pads amid a maze of SMD, mate....it's been fun! I tell you though, some of these drives [and obviously my Meegee!], are tough as. I've had a few 'moments' along the way....tripped my PSU umpteen times [where'd that spark come from?], hooked the power up to the drive wrong..[what's that smell??? Uh-Oh!], and had the drive spasming all over the bench [no, that can't be it!], but so far, the drives have eventually come good showing no ill-effects for all my abuse. Quite surprizing, I thought. Anyhow, I refer you to MD_24 for all the particulars of the interface, cable hook-up and pin assignments. That article specifies a 7437 or 7438 as one of it's chips....and both these also seem to have been relegated to the ranks of the 'digitally extinct', so I use instead , a 74HC00 and a 74HC74. This might be why I'm having difficulty with the diskchange function.....but I haven't really tried to nut it out in full yet. My goal was to get a 3.5" drive on-line cheaply and quickly, and that much has been realized. Next time I feel particularly masochistic, I'll sit down and see if I can get the diskchange signal going properly [ie. at all!], but in the meanwhile, if you change disks or put one in after having booted without a disk...[talking anything BUT DF0: here, because without a disk in DF0:, you're not going to get far; unless you've got a h/drive of course..], then you'll have to install the manual pushbutton switch, or issue the; 1> diskchange DF1: command, to get Meegee to understand this real world happening. I just set the alias 'dc' for "diskchange DF1:" in my shell-startup, I've got enough switches already!! So here's my first 2 successes; Matsushita JU-362-02W; Easy one this. Hook-up the drive/interface as per MD_article. There's 1 row of jumper-pins on the drive's board. Put a jumper on the 'D0' & 'RY' flags. The drive should now behave itself, with motor-control.....and I'll get around to the diskchange signal one day. Matsushita JU-364-03W; [You'd hardly credit such a small offset in model numbers could make so much of a difference....but..] Hook-up the drive/interface as per MD article. I could not get a true logic _low at this drive's end of things.....it's was either -high, or =sumwhereinbetween when it was supposed to be _low. I figured this was due to a pull-up resnet [resistor SIP] on the drive's board, just between the rear connector and the jumper-pins. Rather ingraciously, I grasped this resnet with my pointy-nosed pliers, and wiggled it back and forth, until it broke off it's legs at board level. Crude, but it effectively gave me the logic-levels that I was seeking. Having done that, put a jumper on the 'D0' flag....remove any others. The spin-motor then wouldn't startup. Hold the drive, upside-down, with the disk-opening towards you. Look just your side of the jumper pins, and you'll see [upside-down, of course!] the letters 'IUS', with a tiny arrow pointing away from you. Just to the right of the arrow's tip, there's a small solder-pad next to a similarly sized white dot. [the solder-pad looks all the world like a solder-filled lead-thru hole on the board] Solder a piece of insulated wire from this pad, to the jumper-pin closest the rear connector, of the 'MO' flag. This should latch the spin-motor permanently 'ON', once started. I haven't spent the sort of time on this that I perhaps should. At power-on, the motor is actually off, only when Meegee goes looking for drives, does the motor start-up....which then latches ON, even though the Amiga has finished accessing it, and returned the motor-signal to a logic -high. That theorectically should turn it back off again, but no, obviously I've missed something...or the drive's electronics are too ignorant to listen. Maybe they're not as indestructable as I thought?! Dunno, but the drive works a treat...albeit with no diskchange or real motor-control, though it does have the extra advantage of 'spin cleaning' any disk stuffed in it. In fact, this one is now my DF1:, and it has far and away less problems with read/write errors than any other diskdrive I've ever owned....actually, it hasn't had !ANY! such errors, which is really good going around here. As it is the drive I use, there's a reasonable chance I'll get around to sorting out it's two shortcomings, but no promises. When I get some more time, bits, pieces, and inclination, I'll try tackling the other 3 drives......a pair of TEACs [different models], and a NEC unit. At the price, I really should snaffle-up some more of these old d/drives, before they do become extinct. But, like, I've already got 5, so it's not as though I need any more. However, if anyone wants one [or more], perhaps all sorted with cable/plug/interface and ready to go, contact me somehow [talk to someone at Megadisc...they know where I am], and something could be worked out. I'll let you all know if I have any further wins.... DBM «» 44 «» 44 «» 44 «» 44 «» 44 «» 44 «» 44 «» 44 «»