test-drb May 2005

test-drb@ccmp.vtda.org

248 participants
723 discussions

by jim＠g1jbg.co.uk

Hi, has anyone tried to write a paper tape emulator in BASIC? I've had a go in GW-BASIC, but I suspect that the implementation of the language is too slow to reliably drive the serial port - it doesn't always pick up the paper advance signal (I've tried using both CTS and DCD as inputs). Will I have to go to a machine code routine to get the fast port access? I look forward to replies. Jim. Please see our website the " Vintage Communication Pages" at WWW.G1JBG.CO.UK

19 years, 2 months

Prime PDT-100 terminal

by tponsford＠theriver.com

Hi All, I picked up a Prime computer PDT-100 terminal, sans keyboard, today at the auction. I have not (yet) started to collect Prime computer stuff, so I anybody who want this, It's Free, just pay the shipping. I'm not sure if it works OK, but it does power on! Give me a shout off-list! Cheers Tom

19 years, 2 months

CV Transformer - Capacitor on separate winding ?

by dave04a＠dunfield.com

Hi Guys (well OK - Tony mostly :-), Started looking at the Compupro 8086 S-100 system this evening. As usual during initial power tests - pulled all cards, and began to power-up through variac and series light bulb - Bulb glows brightly as power comes up, suggesting system is drawing far more power than it should, and chassis voltages (+8, +16, -16) fail to come up hardly at all. After investigating, I discovered that there is a large capacitor attached to a separate winding off the transformer. This is a oval metal can capaciter (looks like a cylinder, except that end- on view would be oval). It reads: 4 MF 660 AC 60 HZ RONKEN P81A23405H01 Protected 900 AFC NO PCB'S CONTAINS FLAMMABLE FLUID 2483 Disconnecting this capacitor "cures" the excess current draw and the chassis voltages come up fine (still running through variac at reduced AC voltage with series light bulb as I expect this cap is part of a "line voltage regulator". The transformer is labled "C.V." (Constant Voltage?) I am reluctant to conduct a "full power" test as the light bulb glows and full intensity if I bring the Variac up to 120v with the cap connected - ie: the system is appearing as a very low impedance load - when it should be drawing virtually nothing. Ohm-meter tests of the CAP show that it is NOT shorted, and is functioning as a capacitor (brief current flow when leads reversed). It looks to me as if this Cap is acting as a low impedance load at 60hz and effectively "shorting" the winding that it is connected to, which causes the transformer to draw excessive power. Can anyone explain to me what is going on, and why the unloaded power supply is drawing so much on it's input? A brief tutorial on how this type of supply is supposed to work would be very helpful... Regards, Dave -- dave04a (at) Dave Dunfield dunfield (dot) Firmware development services & tools: www.dunfield.com com Collector of vintage computing equipment: http://www.parse.com/~ddunfield/museum/index.html

19 years, 2 months

Stuff I want - all I want is a "0"

by pete＠dunnington.u-net.com

On Apr 28 2005, 16:58, Brad Parker wrote: > > "Rick Bensene" wrote: > ... > >- A full set of drive select (0-3) plugs for RL01/RL02 drives > > Heh. I could use a "0" myself. > > What does one do when one only has a "1"? > > it works, but i'd like a 0. can I make one out of something else? Look at the fingers on the "1" plug. The protruding finger on each side has two edges which can be long or short, but one of those is just used to tell the drive there's a valid plug inserted. A matchstick makes an effective substitute :-) A zero has short edges on upper and lower left, short on upper right, intermediate on lower right (that last one is the "valid plug" finger). A one has short edges on upper and lower left, long on upper right, intermediate on lower right. A two has short on upper left, long on lower left, short on upper right, intermediate on lower right. A three has short on upper left, long on lower left, long on upper right, intermediate on lower right. ISTR that when I made my own perspex plugs, before I had real ones (other than a "zero"), I found there was no real difference between "short" and "intermediate" -- "short" doesn't move a contact, "long" or "intermediate" does. -- Pete Peter Turnbull Network Manager University of York

19 years, 2 months

Picked up VGB10 manual

by jrkeys＠concentric.net

I picked a new copy of the Digital VGB10 Video Terminal Installation and Operating Information manual at the local Goodwill. It has all the pin outs and is written in several languages.

19 years, 2 months

S-100 (Altair) SRAM board needed badly

by william.layer＠comcast.net

Hi all, I read the recent threads about S-100 hauls, so I'm putting out the request for a SRAM board for the Altair 8800 that I'm putting back together. Just about anything is fine; 1K, 4K, 8K etc. As long as it's static ram, and will work with the original i8080 CPU. Can pay cash. Thanks, Bill -- --------------------------------------------- -. William W. Layer .- -. St. Paul, MN USA .- --------------------------------------------------- -. Cheif bottlewasher, Atma-Sphere Music Systems .- -. http://www.atma-sphere.com .- --------------------------------

19 years, 2 months

Free: broken but possibly fixable sync-on-green monitor

by msokolov＠ivan.Harhan.ORG

Hello fellow ClassicCmp'ers, I have a Viewsonic PT813 21" CRT monitor, a very high-end professional model that I was told used to cost $1800 new (1997), has both DE15 and BNC inputs and supports both PeeCee video and sync on green. Unfortunately it is malfunctioning - the picture is smudged to the point of being totally unreadable. It seems like some component in its circuitry went bad - I don't think it's the CRT - so it's probably fixable. The person who sold it to me has agreed to refund me what I paid for it and let me keep the broken monitor, and OKed me offering it for free to the list. Since I believe it to be fixable, but lack the time, tools and skills necessary to do so, I offer it for free to anyone who thinks he can fix it. If fixed it would make a great monitor for classic computers, and has the added bonus that the VS3100 GPX board firmware is perfectly happy with this monitor connected (as I wrote in my other posts, it often throws up a tantrum with other perfectly good SoG monitors). So if you fix it, it should work beautifully with VS3100 GPX, VS3100 SPX, other DEC and other classic workstations. The monitor is near San Diego, California. If you want it, you must come and pick it up. I lack the materials and skills to properly pack it for shipping (if I shipped it, you would get a pile of broken plastic and glass instead of a bad-but-fixable monitor), and I don't even have a car to take it to a shipping store that could pack it for me. MS

19 years, 2 months

AIM 65 lives

by ajp166＠bellatlantic.net

> >Subject: AIM 65 lives > From: Andy Dannelley <andyda at earthlink.net> > Date: Sun, 01 May 2005 10:15:59 -0700 > To: cctech at classiccmp.org > >Just a note of thanks for help and encouragement. I finally got my AIM >back running again with the help of a local who had some test >equipment. > >First, before getting the help I found several stuck address lines and >cleared them by blowing an brushing and vacuuming. > >We then found that 5 out of 8 2114 RAMs were bad, and the CPU just >didn't have enough oomph. > >After cleaning the board and replacing parts, it works like a charm. >Seems weird that the CPU and RAM went bad just sitting, and the board >got something stuck in the address lines just sitting in the box for 20 >years, It was the original shipping box for the AIM, but I guess more >crud got in the box than I realized. People forget that plastic cased parts are not hermetic and therefore subject to internal corrosion and failure. The other is even assembled boards are susceptable to ESD damage. The last is I have brough many boards with odd problem back to life by running them through the dishwasher. I've seen odd failures due to conductive grunge on the board that could not bee seen with the naked eye. Last some brands and styles of scokets really didn't stand the test of time. I have a few NS* boards I've desocketed and soldered the chips directly in becuase of that. Allison

19 years, 2 months

Free: broken but possibly fixable sync-on-green monitor

by ajp166＠bellatlantic.net

> >Subject: Re: Free: broken but possibly fixable sync-on-green monitor > From: Jim Leonard <trixter at oldskool.org> > Date: Mon, 02 May 2005 15:25:48 -0500 > To: General Discussion: On-Topic and Off-Topic Posts <cctalk at classiccmp.org> > >Tony Duell wrote: >> A word of warning to anyone who gets this... I had an Apple Mac+ that had >> a smeared display -- shaddows to the right of objects on the screen. Now, >> the Mac+ video circuit is pretty simple, but none-the-less I spent quite >> a time going through it, unable to find the fault. >> >> The reason I couldn't find a fault in the video amplifier was that there >> wasn't one. It was the CRT. Low emission, I think. >> >> Most of the time, a smeared picture _is_ a fault in the video amplifier, >> though. But it may not be. > >I had a trintron tube connected to the same computer for 8 years slowly go >"smeary" on me and I never found out why (monitor was on for only 3-4 hours >each day, not 24/7). The "smears" were always after a high-to-low or >low-to-high contrast (ie biggest voltage change) on the screen and were always >in the direction of the scan (ie left to right, eventually fading out at the >far right). Video card never failed once, and produced a perfect picture on a >new monitor. > >So what caused that? What went "bad" over time to cause such a thing, and is >it fixable? Actually the most common thing I've seen short of a complete horizonal output failure is the CRT focus pot and associated resistor string fails. It's a gradual failure and for most color monitors that's part of the HV transformer assembly. A few I'e stretched the life by adjusting the focus but sooner or later it fails and the images are just plain fuzzy. I think currently I have 4 in the garage that have either focus or horizonal output problems. Anyone wants to pick them up and a few working tubes give me a email. Allison

19 years, 2 months

RA7x OCP pinout

by ml＠hejoe.de

The are 20 pins at the RA7x OCP interface. I found RA81 OCP pins, but this is different. Can anybody help with a pinout or link? Michael

19 years, 2 months

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test-drb May 2005