test-drb September 2000

test-drb@ccmp.vtda.org

156 participants
405 discussions

by geoff＠pkworks.com

>> >> Good thing you didn't take the cap off the side of the tube, as you're >> looking at something like 18KV there. DON'T EVER GO INSIDE A RUNNING OR >> RECENTLY POWERED OFF MONITOR OR TV WITH A CRT UNLESS YOU KNOW WHAT >> YOU'RE DOING. You could easily be electrocuted, and that would be, as >> they say, "bad." > >IMHO the EHT (the high voltage to the final anode in the CRT) is about >the least likely supply in a monitor to give you a dangerous shock. There >are 2 good reasons for this : The mains supply is obviously the most powerful voltage source in a VT320, but it is entirely wrong to dismiss the anode voltage, for two reasons. 1. My intention was to serve a warning, not to debate the merits of which and what. Somebody who admits to being in over their head, and who managed to blow the vacuum in a CRT and who doesn't recognize the symptoms, may well not know about the possible effect of anode voltage on the human organism - specifically, their own organism. If you've ever gotten across a CRT's anode voltage - as I have - it will knock you right on your ass. 'Hurts like hell, too. Yes, I know it's a high-impedance source whose voltage drops as the current rises, but if it does 100uA at 18KV, how much does it do at 100V? Making several assumptions, 18mA at 100V is quite enough to kill you if you just happen to do it right. And are you any less dead than if you'd plugged yourself into mains current? If you get run over by an automobile are you any less dead than if you got run over by a bus? *ANY* voltage source is worthy of respect. Anything over about 40V or so can be fatal in the right circumstances and I've gotten nasty tickles off 48V phone lines on hot days when I was sweaty and foolishly not being attentive to what I was doing. I've seen people weld themselves to 5V busses with their wedding rings, and suffer serious burns in consequence. 2. Unlike the mains supply, which "goes away" when you unplug the VT320, the CRT anode voltage takes a long time to discharge. I've had TVs take a day to do so. This is often surprising to novices, who sometimes learn the fact the hard way. > >2) The EHT is pretty hard to get at in modern monitors. It's produced >inside the potted flyback transformer/rectifier assembly and sent to the >CRT connector. Everything is well insulated. You're not going to touch it >by accident. Agreed, but here was a poster talking about removing the anode connector >from the CRT, presumably soon after powering the unit down. A classic invitation to "surprise" as ever I've heard one. Also, insulation on flybacks and the anode voltage lead is in an electrically stressful and hot environment, and sometimes gets friable with age. (I've got an old flyback in a junk box in my basement that amply demonstrates the phenomenon.) Even without attempting to remove the anode connector touching the wrong "insulated" thing in an old terminal without first discharging things can be very unpleasant. If you feel that getting across the anode voltage in a VT320 terminal is safe, that dying is unlikely, and that you're adamant enough about it to write to a newsgroup with your views, I ask you please not demonstrate your claims to attempt to prove your point. My whole purpose in making the capitalized comments in my original post was to save lives, not take them. Unless you've got a damned good reason to do otherwise, *ALWAYS* power off what you're working on before poking around inside, and make *CERTAIN* all the high-voltage nodes are discharged. And if for some damn-fool reason you can't do that, whenever you're poking around in circuitry with even a chance of getting a shock, take precautions. (And if you're uncertain, presume there is a shock hazard, and it is high.) In particular, keep one hand in your pocket and wear well insulated shoes on a dry floor. That way, even if you do touch something nasty the current path is less likely to be through your heart. This is *NOT* a sufficient rule, it is merely the first of many, but it is very easy to do and has saved many lives. Everybody, take care out there, OK?

23 years, 6 months

Slowly blowing a CRT?

by dhquebbeman＠theestopinalgroup.com

> >DON'T EVER GO INSIDE A RUNNING OR RECENTLY POWERED OFF > >MONITOR OR TV WITH A CRT UNLESS YOU KNOW WHAT YOU'RE DOING. > > Just how recently would recently be? Just get out your welding cables and triple layers of rubber gloves, connect one end of the cable to the nearest water pipe, then wedge the tip of an aluminum welding rod up underneath the flyback's attachment to the crt, and prepare for fireworks. YMMV. 8D -dq

23 years, 6 months

VT320 connector

by dhquebbeman＠theestopinalgroup.com

> [VT320 cabling] > > > (a) Separate DB25 (female or male) with DEC cable offset > > > connection along with a separate cable with the DEC offset > > > at each end > > > > The connector is the 6-pin MMP (Moulded Modular Plug ISTR) > which normally > > I've always called them MMJs (Modified Modular Jack IIRC). > Does anyone know which of us (if either) is nearer the truth? On mine, the connector lacks any designation; however, the cable says "DECconnect Office Cable". -dq

23 years, 6 months

[OT^2] Re: Our fine educational system (was: Login on VMS)

by dhquebbeman＠theestopinalgroup.com

> Peter Joules wrote on 9/27/00 4:28 pm: > > >> I think I managed to hit > >100+MPH on a few occasions. > >> > >> WHEEEEEEE!! > > > >I thought all Americans drove > >at no more than the 50? > >limit ;-) > > > >-- > >Regards > >Pete > > > not really. My friends and I went out mischiefing one > evening.l didn't drive so my friend took us. We hit 130 mph > on the local highway. Ok, until recently (every suspension component needs replacing) my '86 Quattro was pretty fast... on a long flat section of I-64 in southern Indiana, I had it up to 140mph. I think the car had more to give, but my cajones max out at 140. And just to get this back on topic, stock, this car won't go that fast, but I modified the engine controller, a 6805-based embedded processor, by customizing the ROM to not dump the turbo's boost out the wastegate as soon (stock, boost maxes out at 1.3bar, but mine makes it up to 1.8bar), and by adding a bit more fuel via the fuel frequency valve to keep from putting holes in the tops of the pistons. Since the engine controller, like the car, was built in 1986, it vaguely qualifies as being over 10 years old. Stomp on that accelerator, then: one-mississippi, two mississippi, Whoosh! -doug q

23 years, 6 months

cloning VMS installs?

by cmcmanis＠mcmanis.com

Hi everyone, I'm trying to do fairly complete VMS installs on several machines before Saturday and I was wondering if there was a better way. Specifically, is it possible to create a standalone backup of a freshly installed system and then restore that on several machines ? (I realize that you have to replace the VAX-VMS license but other than that, and changing the SCSNODE and SCSSYSTEMID is that all that is necessary? --Chuck

23 years, 6 months

3b2 tape request

by jwest＠mppw.com

Greetings folks; I have a friend who got into 3b2 gear recently. He needs a boot tape for SYSV322. Aparently the boot code for his system has some special code for his model so not just any 3b2 boot tape will work? His system is a 3b2/600G. Can anyone help? Jay West

23 years, 6 months

VCF

by fauradon＠mn.mediaone.net

Hi, See you all tomorrow at the VCF. For those who care I'll be wearing a TOPO TOPO TOPO TOPO HELLLLO T-Shirt. I hope to get to meet some of you... Francois

23 years, 6 months

cloning VMS installs?

by agraham＠ccat.co.uk

I don't see why not; VMS itself isn't tied into the SID of the machine. Obviously just install onto one disk in one machine then transfer that vanilla install via STABACKIT onto the others....I gather we're talking VAXen here? I love booting standalone backup off tape.....:o) Not. What I've done in the past is install onto one system then put that disk into the next machine and image backup across onto another one etc.....ISTR there weren't any problems, but it was a few years ago! a > -----Original Message----- > From: Chuck McManis [mailto:cmcmanis@mcmanis.com] > Sent: 29 September 2000 07:40 > To: classiccmp(a)classiccmp.org > Subject: cloning VMS installs? > > > Hi everyone, I'm trying to do fairly complete VMS installs on several > machines before Saturday and I was wondering if there was a > better way. > Specifically, is it possible to create a standalone backup of > a freshly > installed system and then restore that on several machines ? > (I realize > that you have to replace the VAX-VMS license but other than that, and > changing the SCSNODE and SCSSYSTEMID is that all that is necessary? > > --Chuck >

23 years, 6 months

VT320 connector

by agraham＠ccat.co.uk

They're both true :) The MMJ (jack) is what you plug an MMP (plug) into! > -----Original Message----- > From: ard(a)p850ug1.demon.co.uk [mailto:ard@p850ug1.demon.co.uk] > Sent: 28 September 2000 21:04 > To: classiccmp(a)classiccmp.org > Subject: Re: VT320 connector > > > [VT320 cabling] > > > (a) Separate DB25 (female or male) with DEC cable offset > > > connection along with a separate cable with the DEC offset > > > at each end > > > > The connector is the 6-pin MMP (Moulded Modular Plug ISTR) > which normally > > I've always called them MMJs (Modified Modular Jack IIRC). > Does anyone > know which of us (if either) is nearer the truth? > > -tony >

23 years, 6 months

VT320 connector

by ajp166＠bellatlantic.net

From: Tony Duell <ard(a)p850ug1.demon.co.uk> >I've always called them MMJs (Modified Modular Jack IIRC). Does anyone >know which of us (if either) is nearer the truth? > >-tony Tony is correct. That is the DEC description and usage save for here we do use both jack and the plug that goes into it. So MMJ is the most common MMP with it being Modified Modular Plug is right but uncommon. Allison

23 years, 6 months

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test-drb September 2000