test-drb August 2014

test-drb@ccmp.vtda.org

213 participants
244 discussions

by drlegendre＠gmail.com

I haven't had a chance to catch up on the new posts, way busy. But I +did+ fix the permissions issues with my info archive at http://nerp.net/~legendre/altair. Need to pay more attention to permissions when using scp.. Steve's new 4K DRAM schematics will be there in a moment, thank you, Steve. On Wed, Aug 27, 2014 at 11:03 AM, Bill Sudbrink <wh.sudbrink at verizon.net> wrote: > > -----Original Message----- > > From: cctalk-bounces at classiccmp.org [mailto:cctalk- > > bounces at classiccmp.org] On Behalf Of William Donzelli > > Sent: Wednesday, August 27, 2014 11:20 AM > > To: General Discussion: On-Topic and Off-Topic Posts > > Subject: Re: Some Altair questions, if I may.. > > > > > At a previous employer where we were doing *bringup* of new > > processors on > > > new hardware (Intel Core2 stuff...before the memory controller was > > integrated > > > in with the CPU) we had a "front side bus analyzer". It was "double > > pumped" > > > and running at 800MHz (so logically it's running at 1.6GHz). As I > > recall that > > > analyzer was in the high $100,000s (ie pushing $1,000,000). > > > > And in 20 years, that same item will be a $100 hamfest special. > > With the pods and data cables missing. Where the h*** do they go? > > >

10 years, 3 months

TTL source/sink currents and LEDs (was Re: Some Altair questions, if I may..)

by spacewar＠gmail.com

On Sun, Aug 24, 2014 at 2:06 PM, Tony Duell <ard at p850ug1.demon.co.uk> wrote: > This is quite a nroaml way to do it. A TTL output can sink a larger > current tahn it can source, By which Tony means "can sink a **MUCH** larger current than it can source". If you look at the spec for the TI SN7404, the difference is a factor of 40: max -0.4 mA source (high), vs. max 16 mA sink (low). Generally speaking, 0.4mA is nowhere near enough to be usable for an LED, so driving the low side of the LED was the only practical approach with normal TTL. Even the max sink spec of 16mA wasn't enough to drive a typical mid-1970s red LED very brightly. For example, a Monsanto (later GI) MV5020 red LED at 20 mA would only give you 2.0 mcd typical (and 0.6 mcd minimum!). That very low source current spec (-0.4 mA) is about the same for all true TTL families, excepting some buffer parts that are spec'd able to source more current. Modern CMOS parts tend to have closer or even identical source and sink limits, so it has become somewhat more common to see high-side drive for LEDs, though many designers have stuck with low-side drive out of tradition. Many modern LEDs are also much more efficient than those from the 1970s, which is partially because different chemistries producing lower wavelengths are commonly used for red, e.g., 620-340 nm vs. 660 nm, and the human eye is significantly more sensitive to the lower wavelength. However, the modern chemistries are also more efficient in terms of absolute light output per current. A representative modern T1 3/4 LED with comparable spatial distribution to the MV5020 is the Cree C503B-RCS-CW0Z0AA1, which has a typical wavelength of 624 nm, and typical luminous intensity of 5100 mcd (minimum 3000 mcd) at 20 mA. When comparing LED specs, it is important to look at the spatial distribution. A narrow viewing angle LED will give higher luminous intensity but only on-axis. Eric

10 years, 3 months

Test Loads for Power Supplies

by robert.jarratt＠ntlworld.com

I have some machines which I have had a while and which I have yet to power on. I am a little wary of just switching them on and hoping they will work, being concerned that if they are not right they may damage something in the machine. Since a switched mode PSU needs a load to work properly, what do people use as a dummy test load for power supplies? I was thinking of building a small board with a bunch of resistors on it and suitable connectors (particularly the molex one common in most PCs). Maybe switchable in some way to vary the amount of power consumed. Good idea? Would it make sense to test the outputs of the PSU (for voltage and ripple) just at the minimum power, or would it make sense to test the maximum rated power consumption, or perhaps both? I believe there are test instruments for this kind of thing, but that they are very, very expensive. Regards Rob

10 years, 3 months

OT: Inexpensive & available plug-n-play WiFi for Linux

by drlegendre＠gmail.com

Working on the assumption that there is a fair amount of Linux / OSS users on the list.. Support for WiFi hardware has long been a thorn in the side of Linux users - what product to buy, which chipset will it have, will it actually arrive with the correct rev of the correct chipset, will the latest kernel support it, etc etc. But I've come across a line of product which works so well I have to put it out there.. It's the stuff based on the RALINK RT-5370 chipset. So far all I have are USB-based adapters, but they are 100% plug-n-play under recent Ubuntu OSes and seem utterly bulletproof. Fast, too! I have tried both the tiny white 'chicklet' adapter as well as the more conventional type with an external antenna, and both types perform beautifully. They can be had for as little as $3.65 +shipped+ from China, or around $8.95 from US sellers. I now own three. Literally stunned at how well they work - plug it in, type in your network pw and go. As I understand it, the chipset mfr. opened the specs for the Arduino developers, and the adapters are targeted at Arduino users - at least that's how they're advertised on eBay. But they sure work fine in my commodity PC hardware.. What a pleasure!

10 years, 3 months

Test Loads for Power Supplies

by marc.verdiell＠gmail.com

I use 10 Ohm 10 or 25W resistors, 2 or more of them in parallel, depending how much current you want to draw. They look like white rectangular bars. They have them on the shelf at my Fry's electronics store. For what it's worth, on the latest power supply I tried, just one resistor was not enough to start the supply, I needed 2 to draw at least 1A from the 5V and then it was OK.

10 years, 3 months

Portable Facepalm II

by nf6x＠nf6x.net

I'm working on a Kaypro II that I recently bought. The poor thing has suffered at the hands of a previous owner. Among other indignities, the brightness control and reset button were relocated from the back panel to the front for easy access. It appears that the brightness control was just a potentiometer in series with the unshielded video cable between the main board and monitor (assuming that the previous owner just moved it, and didn't change the overall design). The original wires weren't long enough, so he soldered a few feet of small-gauge speaker cord onto the potentiometer, and then spliced it to the video cable with wire nuts. Wire nuts. In the video signal path. WIRE. NUTS. Big orange ones. In the video signal path. I'll make a blog post soon with pictures, but I just couldn't wait to share this. There are several poorly-soldered patches on the mainboard that I'll need to look into to determine if they should stay. One of the lifted pins has broken off, so I'll be doing some repairs for sure. The front panel also grew a toggle switch which is connected to a small board plugged into the CPU socket, with a Z80B and a few other chips on it. The board is marked "(C) 1983 ADVENT PRODUCTS, INC.", and I'll want to figure out what it does so I can determine whether it's something that I want to keep in there. Another mod (?) is a ROM chip marked "Kaypro 8 PRO MONITOR (c)1984 Micro Cornucopia". It has a lifted pin and a badly-soldered wire attached. The machine arrived with some of the internal cables disconnected, and I'm not ready to try applying power to it yet. -- Mark J. Blair, NF6X <nf6x at nf6x.net> http://www.nf6x.net/

10 years, 3 months

Commodore, Atari, TI/99, etc. are gone

by sales＠elecplus.com

All of these are gone, except for some AC adapters. Some Tandy 1000 series left. No Apple II or IIe, just lots of Apple/Mac laptops. Lots of classic IBM compatible laptops, from 8088 to P3, various stages of completeness, mostly untested. Cindy Croxton Electronics Plus 1613 Water Street Kerrville, TX 78028 830-792-3400 phone 830-792-3404 fax sales at elecplus.com AOL IM elcpls

10 years, 3 months

DE9 pigtail pinouts

by dgriffi＠cs.csubak.edu

While I'm prepping parts for P112 kits, I started thinking about DE-9 pigtails. These things come in two different pinouts. One of them is pin-1 of the header connects to pin-1 on the DE-9. When wiring up a pigtail like this manually, you cut the ribbon cable into two sections. One sections goes on the top row of the DE-9. The other section goes on the bottom. The other one has the pins interleaved. See http://661.org/p112/files/pigtail.pdf for what I mean. The P112 was designed with the second pinout in mind. When I bought pigtails for my first run of P112s, I managed to get that kind. For subsequent runs, I always got the first kind. Which pinout is more common with actual devices? I ask this because I'm tinkering with an amateur radio project that will eventually use DE-9 pigtails. -- David Griffith dgriffi at cs.csubak.edu A: Because it fouls the order in which people normally read text. Q: Why is top-posting such a bad thing? A: Top-posting. Q: What is the most annoying thing in e-mail?

10 years, 3 months

Radio Shack computer desk for Model II?

by nf6x＠nf6x.net

Here's another long shot: Does anybody near southern California have one of the Radio Shack computer desks that were configured to hold a Model II that they might consider parting with, like the one in this catalog page? http://www.radioshackcatalogs.com/html/catalogs_extra/1979_rsc-03/h002.html Or any of the other computer desks sold by Radio Shack for the TRS-80 machines, for that matter? -- Mark J. Blair, NF6X <nf6x at nf6x.net> http://www.nf6x.net/

10 years, 3 months

Help? Any Data General DG10 documentation/software available

by colineby＠isallthat.com

Hi ? Thought I?d see if there were any list members who could provide background information on the Data General DG10. We?ve received a working system as a donation, but there?s no software or documentation with it. I understand the hardware was very specific to the model since it used a MICROeclipse coupled to an i8086. What I don?t know is whether we need to locate model specific disk images to run AOS or RDOS on it. Also not sure how specific application code has to be. It would be useful to find service manuals, programming manuals and media. I understand Wild Hare Computers was working on an archive, but there doesn?t seem to be much in the public domain as yet. Can anyone offer any guidance? Thanks Colin

10 years, 3 months

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test-drb August 2014