test-drb July 2006

test-drb@ccmp.vtda.org

204 participants
377 discussions

Powering (or not) a parallel-port-attached DAC (was Re: Vector Imagery)

by ethan.dicks＠gmail.com

On 7/4/06, Tony Duell <ard at p850ug1.demon.co.uk> wrote: > Obviously you might well not be able to do this. In which case, you > either have to buffer the port lines (to reduce the output impedance > there) or add a buffer amplifier on the analogue output. Either solution > involves active components that need power. I know that the "right" way to do it involves active components... given my 95% success with passive components, I was hoping to squeak by. If I could get power and data from the same source (see below), I wouldn't be quite so picky. > Can't you grab power from the computer? Obvious places would be either > the keynoard connector or the joystick port. Keyboard connector is a possibility. This (server-class) computer doesn't have a joystick port. As I mentioned in another message, my breadboard is extracting power for projects from the USB port (cable came from a dead keyboard), but I really don't think the mechanical arrangement is viable in a user environment. We've lost three of these machines in 12 months by static discharge when plugging in USB devices - you can see the resultant hole in the epoxy of the gate array that does the USB... the machine is totally fried after a spark... I'd prefer to glue the cover shut to keep users out; I certainly don't want to leave a device behind that encourages them to fiddle with the front USB ports. No... we don't have any powered USB hubs here - the ports the vendor designs in are the ports we have to work with. I'd probably be best served by rigging up a back bracket with a custom power cable - that way, at least, it'd be out of sight, out of mind when installed. > I have never forgivven IBM for not putting a +5V line on the parallel > port. It would be so useful for homebrew add-ons. I have modified a few > parallel cards (cut and jumper in the obvious way) so that pin 25 is a > +5V output, the problem then is that any normal printer cable will short > the 5V line to ground. That's a nice hack, and one I might have done for myself back in the ISA days, but as I mentioned in another message, an official +5V output pin on the Amiga 1000 caused lots of people lots of grief and C= relented with the A500 and A2000 and went with a totally PC-printer-cable-compatible port after the A1000. I've seen some goofy designs for getting power to an external device - molded DB25s with integral coaxial power connector (for an early powered mouse), and more than one design for a male/female keyboard power connector (Xircom did one for their PE3 Pocket Ethernet Adapters)... it would have been so much easier if there had been an official way to tap power. > > two, because I'm at the South Pole and I have to work with what I have > > on hand - there won't be another plane for nearly 4 months. > > Ah, and you don't have any DACs in the junk box... We have many, many parts in drawers (I probably have access to 20-25 parts bins), but DACs are not among them. I might be able to scrounge something off of a dead board (we have some Vaisala weathersonde boards and some UPS boards in the scrap pile - I did manage to score 16 IRF510s from a dead UPS a couple of months ago, perfect for a thermo-controlled fan ;-) > But do you have suitable resistors? I've not done the calculations, but intuitively, you > need the R's and 2*R's all to agree to better than 0.5% for an 8 bit > converter. 0.5% resistors are not common. Ah... we have quantities of 1% resistors, but no 0.5% resistors that I know of. As for my simple 8-value DAC, I used 5% resistors and hand-sorted them for a (nearly) consistent 1:2 ratio up the line. We have a number of the ancient Ohmite red drawers with a dozen values per tray (there are lots of components here from the 1960s, including a bucket full of tubes/valves). -ethan

17 years, 10 months

can you indentify this rack slide?

by aek＠bitsavers.org

> can you indentify this rack slide? Chassis-Trak

17 years, 10 months

T300 exerciser

by aek＠bitsavers.org

> ps: any chance you have a box for a century data drive? I have a few of them, if you have a drive clean enough to attempt a head load.

17 years, 10 months

Rk05 suitcase exercisor?

by brad＠heeltoe.com

Hi all I've heard rumors that an RK05 suitcase exercisor exists. Has anyone ever seen one or used one? Does anyone have one? I assume it would connect via the "unibus" connector and exercise the drive (seek, read, write, etc...) -brad

17 years, 10 months

ne1 got a Proprinter II (parts machine)

by chrism3667＠yahoo.com

I need one plastic part to make this one complete. E-mail me offlist please. Thankee. __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com

17 years, 10 months

ESD disc drive papers

by aek＠bitsavers.org

I turned these up looking for something else this morning http://www.wallash.com/publications Related to Billy's postings a while back about ESD issues in disc drives and why it is more of an issue in modern drives.

17 years, 10 months

Microfilm scanning - film scanners?

by philpem＠dsl.pipex.com

Hi, I've been skimming the recent threads on microfiche scanning with some interest. Just out of curiosity, has anyone tried scanning microfilm/microfiche with a film scanner? Just interested, because VueScan (free trial from www.hamrick.com, $50 for the basic licence, $90 for the 'professional' licence) seems to have a setting for microfilm scanning. Unfortunately I don't have any microfilm to try it out, but my film scanner (a Minolta DiMAGE Scan Dual IV) only takes mounted 35mm slides and 35mm strip film, so anything I put in would have to meet those size constraints... I could (in theory at least) bodge up a cardboard carrier for my flatbed scanner (an Epson Perfection 2400 Photo) and use that, but I don't rate its optical quality for transparency film very highly. I was just curious if anyone had considered trying it... I'd love to but like I said, I haven't got any film to test with. -- Phil. | Kitsune: Acorn RiscPC SA202 64M+6G ViewFinder philpem at dsl.pipex.com | Cheetah: Athlon64 3200+ A8VDeluxeV2 512M+100G http://www.philpem.me.uk/ | Tiger: Toshiba SatPro4600 Celeron700 256M+40G

17 years, 10 months

On the subject of AXP-VMS V7.3-1

by compoobah＠valleyimplants.com

Does anyone else need it?

17 years, 10 months

Does a Kensington Expert Mouse need an external adapter?

by ethan.dicks＠gmail.com

I have this Kensington Expert Mouse here (c. 1995), and I'm wondering if I'm missing an external adapter box... it has a Mac-style DIN-8 for a connector, and inside, I see 3 chips - an LM358 near the DIN-8, an LP339N (quad comparator?) and a 24-pin Motorola SC417907P with an adjacent 4.00MHz crystal resonator, clearly some sort of microcontroller being used as a mouse protocol encoder. One mysterious part is the optical receiver, an SD6150... it's an acrylic-housed device with a visible silicon die, and 5 leads. It's positioned to catch the light off of the marked roller that catches light from an IR diode, so it's got to be something like a multiple-element photodiode (they are marked "DTC1" and "DTC2"), but googling isn't not revealing any hard details on the part. I _think_ I can see 4 "panels" on the die, so it might be a Common lead and 4 light sensitive patches that the board would use to turn a strobed light from the roller into both phases of the quadrature waveform. I don't think the folks that once used this had old Macs (perhaps they did 10 years ago), so my first thought is... what protocol might this speak and am I missing an external adapter to, say, a PS/2-style mouse cable? Another possibility I can think of is that it is designed to hook to a Microsoft Bus Mouse board (probably have one of those hanging around here somewhere). I did some googling on it and can't find any internals info or any "hack" articles. Honestly, I could use this even if I have to extract raw quadrature and do something with that. It's a single-sided board, so reverse-engineering it is not impossible, but I thought I'd ask first and see if anyone knows some technical details on it. Thanks, -ethan

17 years, 10 months

Does a Kensington Expert Mouse need an external adapter?

by compoobah＠valleyimplants.com

Very likely that it uses an adaptor box. Almost all Macs (exclusive of the Plus) with MiniDIN-8 serial also had MiniDIN-4 ADB interface, which would be what a mouse would use. Even on a Plus I don't see why anyone would go to the trouble of rewriting enough drivers to use the serial ports for a mouse when the mouse port is available and SSW expects its use. Could this be a NeXT trackball?

17 years, 10 months

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test-drb July 2006