Joined: October 8th, 2014, 2:05 pm

September 5th, 2018, 6:42 pm #81

tcurt wrote: With regard to the CRT anode, I'm deciding I need to route it beneath the build deck because the controller board is god-awful ugly and bright green. In order to do that I have to sever the anode wire and re-attach it. I know it's a high-voltage line and I have some suitable shielded single-conductor cabling for it, but does anyone know of a maximum length it can be and/or does it matter?
Doesn't matter. The current through that lead is almost nothing. Shielding isn't really necessary for it either. It doesn't radiate an interfering signal, and the voltage is high enough you'd be hard pressed to couple interference into it that would cause a noticeable effect. Your main concern is the breakdown voltage of the wire's insulation. I don't know the details of your monitor but if it's monochrome I'd expect the voltage to be less than 20 kV. (But then I've been surprised by TVs before, so don't just take my word for it.)

One problem I've seen with open frame monitors is magnetic interference causing the image to wobble from side to side. I worked in an appliance shop back when dinosaurs with vacuum tubes walked the Earth. The boss had a Radio Shack TRS-80 computer set up on a shelf in the TV demo room, but when one of the big TVs nearby was turned on it made the computer's image wobble. You should be fine if you won't be using the terminal near a TV or big electric motor, but if that's a concern you might consider magnetic shielding. (At work we use something called mu metal, but it's not cheap and it's opaque, so it'd cover up much of your hard work.)
If it ain't broke, I'll fix it!
Quote
Like
Share

Joined: September 16th, 2014, 7:01 am

September 5th, 2018, 7:22 pm #82

I'd be more worried about the people with more enhanced senses in your life - I'd walk into the room and holler "Turn That (*Damned*) Thing Off!" because I can hear the high voltage transformer whining - if it has a loose winding and/or a bad potting job and your hearing is still good up past 20K it's downright Loud, and good luck getting someone to fix something they don't even hear. 

Life is so much nicer now that the CRT is an endangered species and flat screens don't use HV.  

And the magnetic fields mess with the deflection coils.  You can shield the source of the fields, or the deflection coils on your CRT.
Quote
Like
Share

Joined: August 16th, 2016, 11:47 am

September 5th, 2018, 7:50 pm #83

I had an RCA tv that drove my brother nuts because of the HV transformer. Didn't bother me.
Quote
Like
Share

Joined: September 16th, 2014, 7:01 am

September 5th, 2018, 8:21 pm #84

Antknot wrote: I had an RCA tv that drove my brother nuts because of the HV transformer. Didn't bother me.
And now you know why you got Coal from him for Christmas.  Of *course* it didn't bother you, so it wasn't a problem... 

So, did you wear earplugs to rock concerts?  I'm betting No, and you sat right up front near the speaker stacks. .
Quote
Like
Share

Joined: August 16th, 2016, 11:47 am

September 5th, 2018, 8:50 pm #85

No concerts worked testing ammo for the GAU-8/A first job out of tech school. 
Quote
Like
Share

Joined: January 11th, 2016, 8:57 pm

September 5th, 2018, 8:52 pm #86

BruceBergman wrote: .....So, did you wear earplugs to rock concerts?  I'm betting No, and you sat right up front near the speaker stacks. .
Like I tell my grandkids, "I may need electric ears these days, but I got to hear - and see - all the great bands that came to Australia!"
Breakfast.com halted. Cereal port not ready.
Quote
Like
Share

Joined: October 8th, 2014, 2:05 pm

September 5th, 2018, 9:00 pm #87

Antknot wrote: No concerts worked testing ammo for the GAU-8/A first job out of tech school. 
Cool! I had a friend who did field service for a company that made batch mixing equipment, and one of his clients was a plant that made (among other things) ammo for the Avenger cannon. He had a photo of an artillery projectile in flight with his name written on it in white paint. He joked that he'd never die because the "bullet with his name on it" had already been fired.
If it ain't broke, I'll fix it!
Quote
Like
Share

Joined: February 17th, 2016, 1:31 am

September 6th, 2018, 12:10 am #88

"magnetic interference" can be fun to watch...at least 1x

?? years ago, I grabbed a 21(ish) inch Sony monitor off the discard pile at work...The gamma was a little off, but I had a then *huge* 85 pound PC monitor for free. It played Eq fine & I even went all "office" setup and put my even put my 70's vintage desk phone right on top of it. Mechanical ringer and everything in a beige phone w/o a single feature.

It stayed up there for a few days...Right up until the 1st time it rang with me sitting at the PC...wow. Somehow the monitor didn't end up with a permanent distortion pattern on the screen.

Is it too late to add a plasma globe to that PC?
Quote
Like
Share

Joined: January 11th, 2016, 8:57 pm

September 6th, 2018, 12:24 am #89

Back in the good old days of Z80s, 64k or RAM and green-screen monitors, I showed a couple of kids what the effect of a magnet was on the (monochrome) screen image when the magnet was brought up close to the screen. The image twisted, and created a 'black hole' where the electron beam was distorted by the field. Rotating and moving the magnet kept the kids happy for - oh, about 7 seconds....

A little later, I had a very irate mother phone me up and berate me for showing her spawn how to wreck her new colour TV - apparently, he wiped his Dad's large magnet all over the screen - and magnetized the steel shadow.mask inside the tube, throwing a fair slab of the screen's colours all over the spectrum. The picture was apparently pretty much unwatchable!

Luckily, pulling the plug out the wall, waiting a few minutes and powering up again about a dozen times let the de-gauss system built into the set eventually kill the magnetic field and restore some semblance of normality.
Breakfast.com halted. Cereal port not ready.
Quote
Like
Share

Joined: August 16th, 2016, 11:47 am

September 6th, 2018, 12:50 am #90

Some monitors have a degauss buton that will work when the monitor is on. Nice light show for a second or so.
Quote
Like
Share