March 2024 - vcf-midatlantic

Not quite O/T....
by Martin A. Flynn 10 Mar '24

10 Mar '24

Background: With the approval of InfoAge management, CDL and it's friends have successful applied for an LPFM license for Camp Evans. The new station is WALL-LP, and will be found at 103.9 MHz To support this, CDL has acquired all of the hardware, including the transmitter, EAS decoder, and a broadcast phone system. We have built a gateway using audiocodes hardware to convert the existing SIP trunking to ISDN-BRI to support the broadcast phone system. So if you want to demo those Livingston Portmasters or other ISDN kit at VCF-E , CDL has the tech you need. Martin

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AT&T 6386 WGS, Olivetti 380 computer, power supply schematic needed
by Sentrytv 10 Mar '24

10 Mar '24

Good afternoon I believe I have posted before with a question about a keyboard for this computer (386-20), but now I have a question about a schematic diagram for the power supply. I am looking to repair the power supply which is currently dead, outputs about .5 V -.5 V and that’s it. Nothing obviously open or shorted. Somebody did have their hands in it prior to me, replacing or at least soldering various transistors. My issue is: I would like to find a schematic diagram for this so that I can do repairs myself. Or at the very least, connect an AT power supply or hook up an ATX power supply to get the computer running. I would need to know what voltages besides the obvious 12 V, 5 V , -12 V ,-5v needed to run this system. If anyone has experience performing such a task, Please contact me directly if necessary. I won’t bring it to the workshop unless I can find someone who knows, and I have a schematic diagram in hand. Thank you Mike Rosen Sent from: My extremely complicated, hand held electronic device.

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Museum: PDP-8 and beyond. Come see it at VCF East
by Douglas Crawford 10 Mar '24

10 Mar '24

THANKS SO MUCH Dave Gesswein for coming to the repair event and lending your PDP-8 expertise to us again for the weekend! The progress you made this weekend is so exciting and encouraging. For those fairly new to VCF MidAtlantic, our Straight-8 has local NJ history with the The Resistors (google it) and came to use in "barn storage" condition. Dave massively restored this machine and continues to lovingly keep it going. These fault discoveries and repairs are wonderful as we leverage this machine pretty hard as the machine is the oldest computer that we can demonstrate at-will anytime in the museum. It's one of two that we can show how front panels work- the other is the HP 1000 minicomputer. Its the only one in octal. (The UNIVAC 1219 is only demo'd at special events.) We now have several demonstration options on the PDP-8: - A "cylon" mode light demo - Create a message on ASR 33 paper tape in readable font - Math demo on the ASR 33 TTY - Music played to a transistor radio via EMI. - Loading a program from paper tape. The programs, including the tape loader, are kept in core memory. Great stuff! We are now trying to decide to demo with the A/D board. There are more plans for DEC restorations in the near term including a 8e & PDP-11 restorations on the short term. These are likely going to run even more impressive demos. On the longer term we'll have much more DEC in the bigger museum space. A year has been spent researching and putting in place thoughtfully selected and documented software demos on all the working microcomputers. This pushing us towards an all new museum experience as we become a "must see" computing history location on the east coast for the general public, STEM, technology college students, and tech industry professional visitors. -- Douglas Crawford VCF Mid-Atlantic Museum Mgr InfoAge Science & History Museums 2201 Marconi Road Wall, NJ 07719

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Workshop results
by David Gesswein 10 Mar '24

10 Mar '24

Worked on straight 8. Reported problem was toggled in RIM loader wouldn't load the BIN loader tape. Verified issue was still occurring. Since we knew we had issues with connection to cards from last workshop cleaned all the processor cards edge fingers and backplane connector using paper/paper towel with contact cleaner. Battled them during restoration of the machine was 9 years ago due to storage conditions. Didn't change symptoms so single stepped through the loader. Found the RTL (Rotate Twice Left) instruction didn't do anything. Traced it to bad transistor in R603 pulse amplifier in PB19. With transistor replaced and after figuring out I loaded the paper tape backwards the machine worked. Processor sensitivity to motion seemed fixed and running finger down cards also didn't cause crash. Memory side was still sensitive so cleaned those also. Luck didn't hold so memory was non functional after cleaning. Tracing signals with scope found timing pulses missing from W300 delay line board. Inspection found cracked solder joints on both of the board. The delay lines are too tall so get pulled on when inserting or removing boards. Think that cracked joints were present and got worse when cards removed for cleaning. After resoldering Still not working. More probing and found one signal for write was not being generated. Inspected transistors on the W300 generating it and noticed one transistor lead was all rusty. Poked it and it disintegrated. With transistor replaced machine now worked. Ran diagnostic set and reloaded demos and declared ready to go. Hopefully the problems on the W300 was causing some of the occasional flaky behavior. All board cleaned except sense amplifier boards that had additional connections. Verified moving them didn't cause crashes. The boards plugged into the memory box also weren't cleaned since they are gold to gold. Also didn't clean front panel cable boards. If I was able to accurate count that high I cleaned 227 edge and backplane connectors. Each has 18 contacts. We discussed enabling the 12 bit A/D that was installed in the machine when we got it. My memory was that wire(s) needed to be removed from the backplane to enable when I looked at it years ago. Maintenance manual says only cards need to be installed. Decision was to get it working removing wires if needed but I finished work on machine at 4pm Sunday so decided not a good time to mess further. A/D can convert with 6 to 12 bits accuracy taking 7.6 to 56.6 microseconds. Input is 0 to -10V. We discussed some what demo to use that would be of interest to the public but not too gimmicky. Still thinking about it. Have Teletype where we can print results or text graph.

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VCF East 2024 - Update #3 livestream 3/9/2024 at 6:30PM EST
by Jeffrey Brace 09 Mar '24

09 Mar '24

Livestream will be here: https://www.youtube.com/live/myVo0ujf3SE?si=p-F9IQEa_CEkLhdT Tonight 3/9/2024 at 6:30PM EST. Information will be posted to website tomorrow: https://vcfed.org/2024/03/09/vcf-east-2024-update-3/ Take care! Jeff Brace VCF National Board Member Chairman & Vice President Vintage Computer Festival East Showrunner VCF Mid-Atlantic Event Manager Vintage Computer Federation is a 501c3 charity https://vcfed.org/ <http://www.vcfed.org/> jeffrey(a)vcfed.org

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ADM3a parts at System Source March Workshop...
by Herbert Johnson 08 Mar '24

08 Mar '24

> Mounting hardware - these mounting "ears" and band were taken from a > Ball CRT with a broken neck. Could be used to mount a different CRT in > an ADM3a. Just a caution on that band - *do not remove band from an intact CRT*. That metal band provides tension on the CRT against the vacuum inside versus 15 pounds per square inch air pressure outside. Yeah, 15 pounds per inch. If an un-banded intact CRT is struck and shatters, those glass shards could be propelled like a glass grenade. Most CRTs break at the neck, or the very tip at the neck. The neck is thin glass. That narrow opening slows and limits the airflow to *into* the CRT which otherwise has very thick glass. These CRTs were designed decades ago with safety in mind. A lot of small terminal and TV CRT's have a band and screw-mounts. There's no need to fuss with that band. Reattach some other kind of "ears" if needed for mounting in another TV or CRT. But I've taken TV CRTs and popped them right into ADM3A's using the same ears. regards, Herb Johnson -- Herbert R. Johnson, New Jersey USA https://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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Marriott VCF-East Hotel Block is Full!
by Chris Fala 08 Mar '24

08 Mar '24

I just noticed that this is no longer available. I should have reserved it two days ago when I had the chance, but I hesitated. If anyone cancels and frees up a room, please let me know.

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ADM3a parts at System Source March Workshop...
by William Sudbrink 08 Mar '24

08 Mar '24

Hi, I will be at the System Source Workshop on March 30,31. I will be bringing a bunch of ADM3a parts, including: (Names are to help identify pictures, web site below) Chassis1 - this blue chassis is an original, serial number 6961 with the 115 volt transformer. Chassis2 - this blue chassis is a type 2 (with the extra venting and cardboard interior), also 115 volts. Chassis3 - this brown chassis is a late type 2. It has no speaker (the speaker was soldered to the mainboard in late type 2). This is a 230 volt transformer unit. Its fuse holder and switch were donated to 115 volt machines a long time ago. Otherwise complete. Clean board - this mainboard has no keycaps but is otherwise physically complete and in good condition. It powers up to a cleared screen with a cursor but shows no activity on key presses. Note that the key switches are present on the board. Dirty board - this mainboard has seen better days. There is some light corrosion on some chip pins and component leads. It has some but not all keycaps. Definitely does not work as it stands. I got it this way and only took it for the lower case ROM which is being used elsewhere. Good monitor - well, good in that it works and has no visible burn in. But... it has terrible cataracts. It has not, fortunately, started leaking. Complete with driver board. Zenith monitor - Has a little screen burn and a couple of scrapes on the glass. I have no compatible driver board for this monitor. Mounting hardware - these mounting "ears" and band were taken from a Ball CRT with a broken neck. Could be used to mount a different CRT in an ADM3a. Driver1 - This is a complete driver board for a Ball CRT. Unfortunately, the anode cap was smashed, but I am including a replacement that will need to be installed. Driver2 - This CRT driver board is incomplete. It has had its HV transformer taken. I _think_ this is also for a Ball CRT but it is different from driver1. Could be useful for repairs. Bracket for mounting the HV transformer is included. Pictures at: http://wsudbrink.dyndns.org:8080/images/adm3a/ Finally I, of course, would like some money for this stuff but more importantly, I do not want to take any of it home with me! I will deal and if it gets late in the day and you're nice, you may take it home for free. Bill Sudbrink -- This email has been checked for viruses by Avast antivirus software. www.avast.com

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VCF East 2024 Speaker Schedule is up!
by Jeffrey Brace 08 Mar '24

08 Mar '24

I don't expect any more changes, so the following is the speaker schedule for VCF East 2024 Friday Schedule <https://vcfed.org/vcf-east-friday-schedule/> Saturday Schedule <https://vcfed.org/vcf-east-saturday-schedule/> Sunday Schedule <https://vcfed.org/vcf-east-sunday-schedule/> Let me know if there are any typos! Jeff Brace Vintage Computer Festival East Showrunner

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Visual 50 terminal troubleshooting
by William Sudbrink 04 Mar '24

04 Mar '24

I have a Visual 50 terminal that I am now troubleshooting. I got it in the late 1980s and it worked fine until 1995. I can't find a good schematic for it or ROM images. Its symptom is that it powers up to continual beep (solid tone, not repeated beeps) with a cursor on the screen. This is not in the troubleshooting table of the manual that I have. I know the keyboard is capacitive foam pads. I was hoping that was the trouble, but it is not. I disassembled the keyboard and removed the old pads, replacing a few with some spares I had from SOL20 repairs. Has anyone corrected this problem before? I suspect that the EPROMs are going. Thanks, Bill Sudbrink -- This email has been checked for viruses by Avast antivirus software. www.avast.com

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