October 2022 - vcf-midatlantic

OT - Makerspace question
by Martin Flynn 22 Oct '22

22 Oct '22

CDL has removed the dead Liebert CRAC system from the Makerspace, freeing up room to potentially set up a dedicated board repair / rework station on the wall common to the classroom. This is what we have to start with: * Hakko C1392B Positioning fixture * Hakko C1390C Omnivise (three) * Hakko FM205 Shop air de-soldering station To validate the concept, how much use would VCF make of this for restoration and workshops? Martin

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VCF Workshop status
by David Gesswein 21 Oct '22

21 Oct '22

Summary 1) PDP-8 Symptom was start/load addr/deposit/exam/cont switches did nothing. Tracked down to bad R302 dual delay/one shot board. Swapped with a spare. Ran diagnostic set and no more problems found. Left normal demos loaded and discussed how to run lunar lander if people want to also demo it. Has long load time from teletype. 2) TI Professional Symptom was keyboard wasn't working. Swapped with keyboard from my TI and it worked fine. Swapped original back and it worked fine. Wiggling things didn't change behavior. Later it was acting up again but didn't have time to investigate much further. Looked to be connection problem at computer end either the motherboard connector or the cable. 3) Xerox Star/8010 Normally it declared fault with Ethernet which we aren't using so use alternate boot key to bypass diagnostics. It is now ignoring the alternate boot key. Tried board from spare machine and it acted as alternate boot key was always down. Alt boot key goes to IOP card. IOP card installed in Connors machine worked fine. Out of time to investigate further. TLDR; 1) PDP-8 Some people were interested in learning more about troubleshooting and operating machine so used time to also show how I approach troubleshooting. Verified reported symptom and that panel lock was not active so pulled out scope and schematics. Looked for paths that would effect multiple front panel switches and found some signals weren't active and traced it to the R302 that starts the chain of pulses to drive the front panel operation. Tested all the diodes with a DVM since they are the most common failure. All looked good. Forgot my transistor tester so used the DVM to test the transistors. They all appeared good. Looked at trying to troubleshoot the card with scope but DEC only released the schematics for the cards but not the component location drawing. Vince has created layouts for a number of cards at https://so-much-stuff.com/pdp8/flipchip/flipchip.php but the early revision card didn't have a layout. Since I had a spare we swapped it in and adjusted the delays and I took the card home to repair. Transistor tester shows one transistor is bad. DVM also shows its bad so did something wrong when I was originally testing and missed it. Will replace transistor and test in my machine before next visit. Showed how to load and run the diagnostics and the Focal lunar lander game. Also showed the board I made to allow the serial port to run at 9600 baud instead of the normal 110 and the current loop to RS-232 board so I could send tape images from the laptop to speed up testing. More of these can be made if others are going to do maintenance. Also noted that the intermittent issue with the machine going into run on power up seems to happen when the machine has been off for a little while. This has been on the todo to fix for a while but normally it won't reproduce after fixing the more serious issues. Probably best to start with this next time. Working around by setting switches to stop at power on/off. Computer corrupts memory if it starts running on power up. 2) TI professional Later when we noticed keyboard was acting up again the symptoms looked like a bad connection at the computer end of the keyboard cable. Didn't have time to verify it its the keyboard cable or the connector on the motherboard. Noticed some clicking from the speaker that changed with wiggling the cable. Likely this means the power or ground signal is the cause and the transients from it going open and closed are getting into the audio. Left keyboard disconnected to avoid the clicking. Didn't have time to investigate further. Note keyboard is not compatible with standard PC keyboard. 3) Xerox The machine has 4 digit diagnostic display and reset and alternate boot buttons to control and monitor boot progress. It was hanging on Ethernet loop test fault (0332). Nothing was connected to AUI port. I brought stuff to connect to see if that would get it past the fault. With AUI transceiver to switch it did get past the fault but faulted with 0323 which is real time clock (RTC) not set. Connor figured out that the keyboard skip/next key would make the machine continue past blinking fault codes. The machine then hung at 0501 which is starting to read the TOD clock. This wasn't a blinking code so couldn't get past it. I also tried booting other images such as Interlisp. It started to put up a desktop then also hung on TOD. The alt boot switch goes to the input output processor (IOP). We pulled the board from the machine in the warehouse and it instead acted like the alt boot switch was always down. This was the symptom seen with that machine when we were testing VCF's two machines originally. The IOP worked fine in Connors machine. Some other fault is causing the problem. Need to investigate schematics and see what could cause problems with reading the alt boot switch and real time clock. Tracing signals Will be a pain since don't have good access for probing signals. The power supply output good lights were all on. I didn't check with DVM. Probably would be good to dig up the test connector pinout to check them. Some comparison with Connors's machine with VCF's was done and with different disk images. The hardware looked to be similar but some of the behaviors and faults were different. Didn't capture details on these tests.

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Z80 systems for $20.00
by Herbert Johnson 21 Oct '22

21 Oct '22

> https://worcester.craigslist.org/sys/d/millbury-retro-z80-computer-new-in-b… > https://museum.eecs.yorku.ca/nabu > https://publications.gc.ca/collections/collection_2018/mstc-cstm/NM33-1-17-… large PDF, look at page 53-55 for "Nabu Manufacturing Corporation" of Canada The following is a lecture on the topic of these devices. Discussion of these units, mis-characterizes them as "Z80 systems". They apparently have a Z80, but they are not "systems" in the way an Apple II or a IBM-PC comparable or modern computers are personal computing systems. In my informed opinion, these are artifacts of an era, one that few people today have experienced; and hard to put to more-familiar use. My informed guess - I don't know, they are new to me - is that these are more fuss than most expect. That's the lecture. https://en.wikipedia.org/wiki/Teletext At a time around 1980, there was a confluence of several technologies. One of course was CRT based color TV's. Another, telephone networks, broadcast TV networks, and also early cable TV networks. Another of course, were 8-bit microprocessors. But it was early days in personal computing, and now-common stuff like mass storage, floppy drives as removable storage, and software - and experience with these by ordinary people - was still in short supply. But people understood things, like newspapers, telephone books, and paper-notes-on-cork bulletin boards. They were used to being information consumers, not producers. Businesses "thought" this way at the time. Again: 1980, don't blame me. So a niche that could be filled, was to build a terminal, that relied on a telecom network (wired phone, cable TV, broadcast TV) to broadcast data; display it on a customer's TV; and accept some slow and short data from a customer keyboard. The customer terminal, only needs to intercept some "page" of data among all the pages sent out, over and over again. These services had various brand names, but "teletext" is adequate to describe most of them. They provided information "narrowcast" and broadcast services; thus they had some incoming revenue, even saving costs (like printed telephone books, as in France as I recall). MOst use was outside the USA. Research of/in the era will flesh this all out. And that explains this Nabu. Apparently a Cable TV terminal. No mass storage because all content is "downloaded". No I/O, except maybe a printer to print notes (coupons for shopping, content to read later). No user programs - user's don't know how to program, the content is supplied. It's a *service*, not a computer - in general. But research shows (the PDF link), it did run some games and some "home" programs like "personal finance". It was in use from 1983 to 1986 (I nailed the date not knowing this.) This unit - I haven't seen the insides, it's unfamiliar to me - apparently has some kind of "slots" for some kind of boards. Due diligence may find details, or reverse engineering may determine the interface AND - and, and - a fair amount of disassembly of the onboard ROMs. Either it's already been done, or someone could assess several to make it worth doing. On value. I think comments like "the keyboards are easily worth $20" are, um, speculative. I've pointed out the challenges of the guts of it. Someone (not me) might be moved to provide some leadership on these, to make something more "vintage computer-ish" out of them. A very smart person, might figure out the head-end protocol to "feed" these devices. But they will have to modulate a cable TV frequency to get it into the box; not simple hardware, not digital. There were all kinds of Z80 based devices produced around 1980. They were purpose built, so it's a kind of a puzzle-to-solve to re-purpose them. Parts value? I guess. Historic value? if that's your mission. If someone has dozens, hundreds of them, it becomes an investment of some sort. These are my observations, bits of research, and some opinions I have; I'm informed on some of this. I'm not looking for a discussion or argument, the focus is this pile of devices and what one might DO with them. I'm providing some context to make more informed decisions. regards Herb Johnson -- Herbert R. Johnson, New Jersey in the USA http://www.retrotechnology.com OR .net preserve, recover, restore 1970's computing email: hjohnson AT retrotechnology DOT com or try later herbjohnson AT comcast DOT net

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Ensoniq Synth for museum?
by Ethan O'Toole 21 Oct '22

21 Oct '22

A few weeks ago there was a request for an Ensoniq ?Mirage? I think for the museum. It's not a mirage, but I run a craigslist ad looking for broken synths to fix. For whatever strange reason like 80% of the emails I get are Ensoniqs. But besides that, someone has an EPS-1. I haven't sniffed out the asking price, but would this be something the museum would want? It is not general midi, but judging by youtube videos it sounds pretty okay. There are some PCBs on tendie to make multicarts for patches which could be cool. Sounds like it's something I could fix. They also said they had either a SQ2 or SQ-80 (can't remember which) but that one is working (no fun.) Not sure the multitimbrality of it. I assume one sound at a time, so could make sequences on the Atari ST using like a Mirage for sampled gritty drums and the EPS-1 for lead/bass? Then an A frame stand for the true 80s. Thoughts? - Ethan

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Re: [vcf-midatlantic] Z80 systems for $20.00
by Stephen A Edwards 21 Oct '22

21 Oct '22

I really hope someone can buy a bunch of these Z80 systems (with keyboards? The keyboards are easily worth $20) and bring them down to InfoAgo where we can buy them. I'd certainly like a couple. If I had a car, I'd drive up and buy a bunch, but I don't have a car.

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Z80 systems for $20.00
by Martin Flynn 20 Oct '22

20 Oct '22

https://worcester.craigslist.org/sys/d/millbury-retro-z80-computer-new-in-b…

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Craigslist ad (Worcester, MA)
by Jeffrey Brace 20 Oct '22

20 Oct '22

Someone alerted me by e-mail the following message: "I am reaching out to spread knowledge about a large batch of 'new-old-stock' vintage z-80 systems <https://en.wikipedia.org/wiki/Zilog_Z80> in storage near Worcester, MA. I am not the seller but came across this local listing a couple weeks ago. After some communication with the seller, I found out that he has more than 2,700 units and is running out of indoor storage. These units are brand new and are being sold for $20 per unit and in bulk for a lower price. They are currently stored outside with minimal weather sealing/protection. I am not affiliated with the seller and have already secured my own unit but I am reaching out in an effort to possibly save these units before they are destroyed by the winter elements. Maybe you know people who have the capacity to take some of these units in? I know this message may seem strange but it is my sincere hope that such fun units can be saved! https://worcester.craigslist.org/sys/d/millbury-retro-z80-computer-new-in-b… " ========================================= Jeff Brace VCF National Board Member Chairman & Vice President Vintage Computer Festival East Showrunner Vintage Computer Federation is a 501c3 charity https://vcfed.org/ <http://www.vcfed.org/> jeffrey(a)vcfed.org

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OT: 3rd Party needs embedded developer - hardware & software
by Neil Cherry 19 Oct '22

19 Oct '22

3rd Party is looking for one embedded developer who knows C++, python, AVR, PSOC. That's hardware and software. Interested parties can contact me and I'll share the details. Local to Holmdel NJ Please don't reply directly to the list, you can use ncherry(a)linuxha.com . -- Linux Home Automation Neil Cherry kd2zrq(a)linuxha.com http://www.linuxha.com/ Main site http://linuxha.blogspot.com/ My HA Blog Author of: Linux Smart Homes For Dummies KD2ZRQ

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Next VCF Swap Meet: June 10, 2023
by Jeffrey Brace 19 Oct '22

19 Oct '22

So I'm choosing June 10, 2023 as our next swap meet. A few reasons for this date: 1) I will be able to get help from the Sea Cadets 2) Doesn't interfere with Father's Day 3) Hopefully doesn't interfere with graduations. 4) Is 8 weeks away from VCF East 5) Is a week and a half after Memorial Day. 6) Hopefully it isn't too terribly hot yet. 7) There is persistent interest in selling vintage computer items! ========================================= Jeff Brace VCF National Board Member Chairman & Vice President Vintage Computer Festival East Showrunner Vintage Computer Federation is a 501c3 charity https://vcfed.org/ <http://www.vcfed.org/> jeffrey(a)vcfed.org

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November Repair Workshop
by Jeffrey Brace 18 Oct '22

18 Oct '22

Just as a reminder. There will be a repair workshop on November 12 & 13. This is the signup sheet: https://docs.google.com/spreadsheets/d/1yGntoKF6NbTq-3LjQVk0GKRbeBXuUBhYCcB… Hope to see you there! ========================================= Jeff Brace VCF National Board Member Chairman & Vice President Vintage Computer Festival East Showrunner Vintage Computer Federation is a 501c3 charity https://vcfed.org/ <http://www.vcfed.org/> jeffrey(a)vcfed.org

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