test-drb

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101090 discussions

by allisonp＠world.std.com

<I'm trying to track-down a mod that Tandy on the Expansion Interface. On o <of my early EIs (SN# 000352), there was a 6-pin DIN modification, which <someone at one time told me was to correct some erratic signal problems. the mod was to bring out ras* cas* and MUX* with terminating resistors at one or both ends. These signals went through the EI cable but timing was critical at best. the later EIs derived cas* and mux* off of ras* inside rather than pipe them over. Generally speaking the mod was one where if it was mostly working it MIGHT help, sometimes it made it worse. There was another mod after that called the buffered EI cable...not a good idea either. Fixing the EI was the solution. Allison

27 years, 11 months

What Classic Computer are All About - A Lovers

by cerebral＠michianatoday.com

At 02:45 PM 7/15/97 -0400, you wrote: > >One last item. MAKE BACKUPS OF EVERYTHING. make duplicate backups and test >the backups for integrity. Disks fail, and the cheapest insurance is a boot >and backup package that works when you replace/repair the offending drive. > > >Allison > This is why I like the 20 and 40 meg drives, I can back up key elements of the OS and configs, and restore them easily. as for 3.5 being more reliable, they are not, as I bought a Conner CFS-850A 850 meg, and it worked nicely for a year, then one day I am greeted with this error: BOOT DISK FAILURE, SYSTEM HALTED. it suffered a head crash, it would spin up normally, and when the controller tested the head actuator upon startup, there was a time when the head would seek to a location on the disk, and GRIND to a halt. the drive never worked again... I lost 700 megs of stuff, half unreplaceable (my fault, but I have no tape drive). fortunately the drive did have a 3 year warrenty, and a replacement was shipped, a 1.2 gig seagate ST-31276A. and here is another question: Is this going to last me more than a year? If Seagate made good drives in the past, will this new one live up to this, or is this drive chock full of corner cutting?

27 years, 11 months

What Classic Computer are All About - A Lovers

by manney＠nwohio.com

> Most 225s were not fails, just retired due to small space available. FYI > you get better results if the disk is LLF'd in situ and well warmed up. That's doubly true for RLL encoded ST-506/412 drives. These drives should be LLF'd from time to time anyway. Most HD controllers have a built-in LLF routine which you can access via DEBUG.

27 years, 11 months

Computer Museums

by IVIE＠cc.usu.edu

> What should be on display considering: > 1) space limitation > 2) Mainframes, minis, micros > 3) What would most attract visitors > 4) What would most attract funding :) I'm afraid number 3 and number 4 will turn you into The Boston Computer Museum. Roger Ivie ivie(a)cc.usu.edu

27 years, 11 months

Some Commie questions

by manney＠nwohio.com

C64 Porer supplies... I have a box full of C64 P/S's ...I sell them for $18 plus S/H, 60 day warranty. Got cables and manuals and lotsa software, too. I don't have any 128's. Anyone wanna get rid of one cheap? Trade a slightly used Panasonic HHP for one :> > >The next question would be, is it worth trying to repair a C64's power > >supply? I got two of them yesterday, both powersupplies are dead. It > >looks like the 5V line is shorted to ground. I did get a copy of the Old & > > if it is potted, NOPE. some are unpotted and can be fixed. > > >New style users manuals, and a copy of "Troubleshooting and Repairing your > >Commodore 64" yesterday (I love Powells Technical Books!) so I've got some > >documentation. It's been too many years since I worked as an Electrician, > >so my skill level is pretty low (wasn't very high to begin with, which is > >why I switched to computers). > > > > I have these manuals too and I must say that it leaves no tern left unstoned. >

27 years, 11 months

What Classic Computer are All About - A Lovers

by KFergason＠aol.com

In a message dated 97-07-15 13:32:57 EDT, you write: << IMHO the ST-4096 FH 80 MG was the most reliable of this era. I spent over 600.00 for this drive new and used it for more than 20 years, and ended up selling it to a business for 50.00 to replace their dead st-251. >> hmm, my experience is just the opposite with this drive. I had 6 out 7 fail in less than 6 months back in 1990. The 4096 was just hideous. Kelly

27 years, 11 months

PC-jr PSU (again!)

by ard＠p850ug1.demon.co.uk

I dug out the PC-jr Techref (in order to look up details on the joystick), and I also looked at the PSU diagrams (page B-23 in my edition). We had a thread on this about a month ago, mainly about the external transformer unit which I don't have. Now, the input connector is a 3-pin thing. The centre pin is connected to shield ground, and then via L3 and L4 on the system board to logic ground. It's thus a DC connection to the system ground. The outside 2 pins go through a filter to the AC terminals of a bridge rectifier (CR7 - CR10) and the output of this goes (via the power switch) to a 1500uF 25V capacitor (C13). The -ve side of this capacitor is also connected to system ground. Thus, IMHO it makes no sense at all for the transformer to be centre-tapped with the tap going to pin 2 on the connector. If it was, the winding would be paritially shorted out by the diodes in the bridge rectifier, which would cause a lot of damage. Also, since C13 is only rated at 25V, the maximum input rms voltage is 25/sqrt(2) volts, which is a lot less than 34V. I therefore still believe that it's a plain 17V transformer between the 2 outer pins on the connector. Incidentally, the +12V output comes from a standard linear regulator, the +5V output from a switching regulator (Z2 is the control IC, Q2 the chopper, and L1 the switching inductor). The -12V output is supplied by a secondary winding on L1, which is then rectifier and smoothed. It's always possible that IBM used several versions of the PSU card, but the schematic in my Techref seems to agree with the one in my machine. -tony

27 years, 11 months

IBM 5161??

by ard＠p850ug1.demon.co.uk

> Haven't found a IBM cassette recorder either but I did pick up an IBM > joystick (had IBM logo on it and the word "Joystick") plus it had a funky > square connector which looked like it goes to the PCjr. I've dug out the PC-jr Techref, and there's some info in it on the joystick.

27 years, 11 months

IBM 5161??

by ard＠p850ug1.demon.co.uk

> (MS-DOS machines) since about 1983 and I have yet to see one. Another > thing I've been looking for without success is an IBM Cassette recorder > for the IBM PC cassette interface. I've heard they really do exist. Now that's something I've never seen. One interesting point is that the pinout of the cassette socket on the PC (although not on the PC-jr) is the same as that on a Tandy Model 1/3/4/Coco/etc It is rumoured that IBM intended you to go down to the local Radio Shack and buy one of their recorders + cable. -tony >

27 years, 11 months

antique computer blowout (fwd)

by kjaeros＠u.washington.edu

Somebody in the Berkeley area might want to answer this call to duty.. I'd be thrilled to get the Sun 1 clone, but it'd cost several hundred dollars to ship up here. ok -r ---------- Forwarded message ---------- Date: 15 Jul 1997 07:39:46 GMT From: Paul Leondis <leondis(a)slip.net> Newsgroups: misc.forsale.computers.workstation Subject: antique computer blowout I'm looking to get rid of some stuff, let me know what you think: I've got a huge amount of old S-100 bus stuff, almost all of it with technical manuals and software on diskette, that was working the last i knew. Most is Godbout stuff, some Morrow, some Dual, etc. Lots of 8" floppy drives and diskettes. I have most of the processor boards that were released by Godbout, including 8088, 8086, Z80, 8080, 68000, and i even have some of the National Semiconductor 32000 series cpus on S-100 cards. I have all the stuff like CP/M 68K with the associated assemblers and linkers etc. I also have a complete working [?] Sun I clone: yes, that's right, the first SUN design was public domain (did you know that?? At least that's the way i understand it...) and a company called Forward Technology made clones of that design. It has a 68K cpu running in a multibus one chassis, and i have lots of peripherals for it, including 9-track tape drive and 1/4" tape drives and disk controllers for several interfaces. I've got all the relevent software, inc. V7 unix and a mess of compilers. I have the (at the time) very high res monochrome monitors that went with the system. It's a real wrench for me to let go of this stuff, if you were in this field 10 or 15 years ago you know what i paid for some of the stuff. But i'm tired of hoarding it all. So, i will take the best offer i can get for all of the stuff. My reserve bid is $0, that is i will give it away if that is the best offer. I will probably be most moved by someone that may actually get some pleasure out of the stuff and esp. someone that would want to take the whole lot. There is a free city dump day coming up in my part of town on July 19th, so i'd like to settle the stuff by then so i can dispose of whatever is left at that time. Paul Leondis leondis(a)slip.net 510-649-0993 phone Berkeley, CA

27 years, 11 months

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