test-drb July 2006

test-drb@ccmp.vtda.org

204 participants
377 discussions

by compoobah＠valleyimplants.com

>no grounded track immediately available, so I'm running the leads across the two channel N outputs. >also tried to chassis/earth ground, didn't make a difference . . . That doesn't make much sense. The scope is across the PSU Channel 4 (-5V) outputs (labeled + and -, I'm pretty sure they are GND and -5V in that order)

18 years, 10 months

Overland Data 3210 parallel port interface?

by cclist＠sydex.com

I've got an OD3210 9-track drive that's been sitting around here for a couple of years. I note that it has a Pertec interface (seems to work) and a parallel port interface. I'm curious about the latter. It appears to be 4-bit each direction, but I don't have a clue as to the protocol or command set. Does anyone have a driver or information about the Overland parallel port interface? Thanks, Chuck

18 years, 10 months

3.5" DSDD disks mostly bad

by dgriffi＠cs.csubak.edu

If anyone wants 3.5" DSDD disks from me, I'm all out. That lot that I posted about last week is mostly bad judging from the sixty I've gone through so far. With 200 to go, I'll just chuck this mess out unless someone here wants to do something silly like make a suit of armour out of floppies. If that's the case, I'll sell the whole lot for the cost of shipping. -- David Griffith dgriffi at cs.csubak.edu A: Because it fouls the order in which people normally read text. Q: Why is top-posting such a bad thing? A: Top-posting. Q: What is the most annoying thing in e-mail?

18 years, 10 months

still having capacitor problems in the IRIS PSU

by compoobah＠valleyimplants.com

I'm starting to get a bit peeved - I've tried randomly throwing capacitors across the output, scientifically choosing a capacitor to have a reactance of 1 ohm at the trouble frequency, and taking that cap and putting another .022?f unit in parallel - and the noise doesn't get attenuated at all, it's still at around 500mV, in high audio frequencies. If it was going down (to ~300 mV) I'd just build a LC choke filter and be done with it, but its stubborn spurning of something that should work is bothering me. Is the ripple carrying that much current that the resistance of the capacitor is an issue? I don't think so- this is a secondary supply (-5V!). I also don't get why there should be a relatively equal AC component in 3 secondary supplies that do share much after the transformer primary, and yet a low level in the main +5V. Could this be something bizarre in the connection of the scope? I'm doing a very bodged scope -> BNC cable (one of the bundle that usually runs to the monitor) -> 2 alligator clip leads stuck on to the relevant bits of the other-end BNC connector. Been trying to work out this board. It's one daughtercard in the PSU, the chopper transisors are on another. Yet, there are 3 TO-3 cased bipolar (2Nxxx parts) scattered amongst the rectifier diodes. Similar units are not present in the +5V channel. Would this have linear regulators on the non-main channels?

18 years, 10 months

Looking For Tandy PC-2 / Sharp PC-1500

by jcwren＠jcwren.com

I've got a friend who was reminiscing his old days in computing, and was thinking he'd like to have his old Tandy PC-2 again. Does anyone have one they're looking to part with (a Sharp PC-1500 would also suffice)? I'd like one that's cosmetically clean, has the cassette/plotter base and manuals. If you have one you're looking to part with, please contact me off-list at jcwren at jcwren.com --jc

18 years, 10 months

still having capacitor problems in the IRIS PSU

by compoobah＠valleyimplants.com

> Forgive a stupid question, Scott--are you taking your ground return for >your scope from the metal chassis or from a grounded track on the PCB? >They might not be the same thing. no grounded track immediately available, so I'm running the leads across the two channel N outputs. also tried to chassis/earth ground, didn't make a difference . . .

18 years, 10 months

IC pin corrosion

by Billy.Pettit＠wdc.com

Tony Duell wrote: UK TVs (even back in the 405 line era) tend to use a 75 ohm coaxial aerial cable (not a flat twin 300 ohm one that's popular in the States). This cable often had an air-spaced insulator between the centre core and the braind, and thus there were channels the full length of the cable. The aerial terminal box had developed a water leak. Rain came in there, ran down the channels in the cable (not down the outside), then came out inside the coaxial plug at the back of the set and ended up on the floor. Of course this messed up the properties of the cable, hence a weak signal and a poor picture. -tony Nice tale and after seeing some of those old coaxials, easy to believe it must have happened more than once. Reminds me of one of my worst memories on the big iron systems. Had a computer that was on the top floor. The building maintenance people were running the grounding cable on the lightning rod down to the earth rod.. And discovered this wonderful cable channel that carried the power from the basement MGs up to the main frame power supplies. The inevitable happened and a lightning bolt took out all the supplies on the entire system. The overvoltage crowbars saved most of the logic. But the lightning literally vaporized the power cables, and the MG was a big piece of toast. Nobody was punished - the union said that there were no guidelines stating this was a bad thing. And common sense seems to be a rare commodity. Billy

18 years, 10 months

VMS program to read/write simh .tap container files?

by bob＠jfcl.com

>At least TPC files are slightly more portable than some formats (RSX-11M+ >Virtual Tape comes to mind). Now if only there were some magic to keep a TK50/TK70/TZ30 drive working for more than ten minutes. And by "working", I mean anything that doesn't require disassembly of the drive and the computer to free a jammed tape. Actually reading the bits is more than I could hope for :-) Bob

18 years, 10 months

DLT and TKxx drives (was Re: VMS program to read/write simh .tap container files?)

by ethan.dicks＠gmail.com

On 7/22/06, Robert Armstrong <bob at jfcl.com> wrote: > Now if only there were some magic to keep a TK50/TK70/TZ30 drive working > for more than ten minutes. Speaking of the drives, I have a small Perl program that will emit the right PostScript to directly print lines of text on the label inserts. Free if anyone wants it. I was tired of handwritten cardboard labels and misaligned laserprinted Avery sticky labels. -ethan

18 years, 10 months

ISO Ultrix 4.x CD images

by aek＠bitsavers.org

Someone I know is working on a DECstation simulation, and is looking for Ultrix to test on it. Anyone have images of the distr discs? Also, FWIW, I found someone who has a simulated 5xxx and O2 running http://gavare.se/gxemul

18 years, 10 months

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test-drb July 2006