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

18 years, 5 months

can you indentify this rack slide?

by aek＠bitsavers.org

> can you indentify this rack slide? Chassis-Trak

18 years, 5 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.

18 years, 5 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

18 years, 5 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

18 years, 5 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.

18 years, 5 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

18 years, 5 months

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

by compoobah＠valleyimplants.com

Does anyone else need it?

18 years, 5 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

18 years, 5 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?

18 years, 5 months

Jump to page:

2024

2023

2022

2021

2020

2019

2018

2017

2016

2015

2014

2013

2012

2011

2010

2009

2008

2007

2006

2005

2004

2003

2002

2001

2000

1999

1998

1997

test-drb July 2006