June 2016 - vcf-midatlantic

Re: [vcf-midatlantic] June 11/12 Workshop - Who's Going? Whatcha working on?
by Todd George 04 Jun '16

04 Jun '16

01-Jeff Brace-Commodore 64 Robotics Kit for HOPE Exhibit 02-Evan Koblentz-Lego LOGO robotics kit for HOPE exhibit (Apple II, IBM PC) 03-Alex Jacocks-PS/2 model 70 and AT&T 6300 testing/repairs (Sunday) 04-Dean Notarnicola - TRS-80 Model 4, Model 4D, Model I 05-Todd George - Not entirely sure, but definitely will bring my AT&T 6300 as well! (I think the highest number was 5... ???) I have an AT&T 6300 with monochrome and color monitors. Monochrome jobby works, color is broken. I've already located and replaced a few bad components, can't seem to get the CRT to come totally alive though. The 6300 works (or worked) when I tested it last. I didn't think anyone else would be bringing them but seeing as Alex is interested, I'll bring mine!! Olivetti/AT&T party!!! WOOT!!! Other than that, I'll probably bring whatever else I'm actively working on by then. As far as current projects, that's going to be a Commodore SX-64, a TRS-80 Model 4P, or a Commodore VIC-20. If I'm a real glutton for punishment, I might bring my Macintosh Color Classic that has had me stumped for months now. Additionally, I'll have my EEPROM burning machine w/some blanks, various parts, and tools including a desoldering iron. I'll also bring a nice oscilloscope. Looking forward to it! -Todd

6 7

hard drive and floppy disk emulator
by Rolf Levenbach 04 Jun '16

04 Jun '16

A MFM & RLL hard drive and floppy disk emulator on eBay: http://www.ebay.ca/itm/-/301968006996 Rolf

4 4

Good source for eproms?
by Herb Johnson 03 Jun '16

03 Jun '16

My comments and questions. Dave McGuire posted: > They can be erased with X-rays. EPROMs were originally designed to be > erased that way. There are problems with that approach, however. (hence > the move to UV). The notion that one can plop non-quartz PROMs under an X-ray and erase them, has been mentioned here, and elsewhere for decades, as a "could be done". But I'm not aware this has been, or is, any sort of common practice, much less an established procedure. I'm aware of 'theory', I know physics. I'm talking accepted practice. Wikipedia....EPROM...citation 6...is a May 10 1971 article from Electonics Magazine by Dov Frohman, who apparently "invented the EPROM". Google..... http://www.jmargolin.com/patents/eprom.htm references the article, and interviews the author later in 1993. The text say Intel shipped that 1702 EPROM "with a window because X-rays ....disrupted the structure" of the chip. The Web page has some details. I"ve not (yet) read the article, or checked the patent. This suggests that X-rays were not a production nor a customer practice. so: Can you cite a reference I can find also, that shows a product announcement, or a production data sheet, that says specifically that a customer can erase a specific PROM product using X-rays of a particular wavelength and energy for a particular period of time? That's how UV exposure is cited (when it was cited in detail) in data sheets. I'll grant the possibility this occurred for some very early product, some early development in the semiconductor lab, or some military or other specialized application. I'll grant some hackers could borrow a dental X-ray and erase an EPROM - did they do subsequent life-tests? Even that description would be of interest. Thank you. Herb Johnson -- Herbert R. Johnson, New Jersey USA http://www.retrotechnology.com OR .net

5 12

Personal ebay score
by Evan Koblentz 03 Jun '16

03 Jun '16

Yesterday I was poking around ebay. Stumbled onto something awesome and it only cost me twelve dollars. I'm a very happy camper. :) Will reveal it when it's in my possession... < insert diabolical laughter >

5 6

HP 1650/1651 Logic Analyzer Disk Images
by Herb Johnson 03 Jun '16

03 Jun '16

http://www.retrotechnology.com/herbs_stuff/386intel/beech_logic.html I have a 1650B, and my Web site shows my colleague Bill Beech and his use of a 1650B on S-100 systems. He'll appreciate that Z80 disassembler, thanks. Herb -- Herbert R. Johnson, New Jersey USA http://www.retrotechnology.com OR .net preservation of 1970's computing email: hjohnson AAT retrotechnology DOTT com alternate: herbjohnson ATT retrotechnology DOTT info

1 0

HP 1650/1651 Logic Analyzer Disk Images
by Systems Glitch 02 Jun '16

02 Jun '16

I picked up a HP 1650A Logic Analyzer at a surplus auction a few months ago, and finally got around to imaging the disks. In addition to the OS and demo disks, I have what is apparently a somewhat rare/sought after copy of the Z80 Inverse Assembler. This lets you disassemble Z80 code right in the logic analyzer. All images were captured with Dave Dunfield's ImageDisk. I've uploaded them here: http://filedump.glitchwrks.com/software/hp_1650/ You should be able to write them out with ImageDisk on a DOS PC with a regular 1.44 MB PC floppy drive. They're double density disks of course. If you have one of these analyzers and can't write disks for some reason, PM me and I can probably mail you some. Thanks, Jonathan

1 0

Repair TRS-80 pocket computer screen
by Christopher Blackmon 02 Jun '16

02 Jun '16

Does anyone know how to repair/replace the screen on a TRS-80 pocket computer? It looks like the edges of the screen are bleeding ink or something. Christopher.

3 2

Re: [vcf-midatlantic] Repair TRS-80 pocket computer screen
by Jonathan Gevaryahu 02 Jun '16

02 Jun '16

Bleeding 'ink', like a black ring which is converging toward the center of the lcd? or squiggly lines of black 'ink' coming from one edge? In either case that's irrepairable, you're going to need a replacement lcd for that. -- Jonathan Gevaryahu jgevaryahu(a)gmail.com jgevaryahu(a)hotmail.com

1 0

TEI MCS-CPU 8080 CPU Board
by Herb Johnson 02 Jun '16

02 Jun '16

Bill Degnan wrote: > I wonder if this is the board Roger Amidon wrote the Apple Monitor for? No, he wrote it for the MITS Altair he bought. Roger said so, in a panel at VCF-East some years ago. You may be confusing "TDL" with "TEI". For TEI docs, I only have docs for the mainframe. Jonathan AKA System Glitch wrote: > I noticed that the layout of the basic CPU function (excluding the add-ons) > is *very* similar to the IMSAI MPU-A. Your Web page is a good examination. It notes even board-trace similarities. It's likely TEI copied the IMSAI and then added their own features. Lots of copying went on in the S-100 era, down to replicating boards completely. If it's that similar, then producing a schematic may be a matter of verifying the board with ohmmeter following (and correcting) the MPU-A schematic. Herb -- Herbert R. Johnson, New Jersey USA http://www.retrotechnology.com OR .net

3 2

Workbench from hell
by Mike Loewen 02 Jun '16

02 Jun '16

Dave McGuire, someone snuck into your shop. :-) https://hackadaycom.files.wordpress.com/2016/05/williams-workbench.jpg Mike Loewen mloewen(a)cpumagic.scol.pa.us Old Technology http://q7.neurotica.com/Oldtech/

8 12