On Fri, 4 Oct 2013, Ian McLaughlin wrote:
On Oct 4, 2013, at 10:56 AM, Cory Smelosky <b4 at gewt.net> wrote:
Yeah. I know they're in the kV range. I'd appropriate discharge the CRT itself...but I lack the appropriate HV grounding wires.
A flat-blade screwdriver and an alligator clip lead. Clip the lead to the shaft of the screwdriver and to the metal chassis of the monitor. Work the flat blade under the rubber cup where the anode wire attaches to the CRT. Be prepared for a loud POP and a flash.
Believe it or not I don't HAVE any alligator clip leads laying around!
CRT is now discharged.
If the loud pop scares you, then you can build a resistor into the grounding lead. I built one of these many many years ago, and it lives in my toolbox for just this event.
Resistors I have plenty of. ;)
Please note that a discharged CRT can build up a static charge again just by sitting on a shelf. Always re-discharge the tube when coming back to a tube you've left alone for a while.
Also, Brian's advice about the hand in the pocket is important. Current is looking for ground. If your other hand is holding the chassis, then the shortest path to ground is across your heart. Not good. From your hand down your leg to ground, while not good, is at least not across your heart.
Ian
--
Cory Smelosky
http://gewt.net Personal stuff
http://gimme-sympathy.org Projects
On 10/04/2013 02:07 PM, Ian McLaughlin wrote:
Please note that a discharged CRT can build up a static charge again
just by sitting on a shelf. Always re-discharge the tube when coming
back to a tube you've left alone for a while.
This is dielectric absorption. It happens with all capacitances,
including capacitance in things that are not capacitors, like CRTs.
-Dave
--
Dave McGuire, AK4HZ
New Kensington, PA
Ian McLaughlin <ian at platinum.net> writes:
On Oct 4, 2013, at 10:56 AM, Cory Smelosky <b4 at gewt.net> wrote:
=20
Yeah. I know they're in the kV range. I'd appropriate discharge the =
CRT itself...but I lack the appropriate HV grounding wires.
=20
A flat-blade screwdriver and an alligator clip lead. Clip the lead to =
the shaft of the screwdriver and to the metal chassis of the monitor. =
Work the flat blade under the rubber cup where the anode wire attaches =
to the CRT. Be prepared for a loud POP and a flash.
CRT is now discharged.
If the loud pop scares you, then you can build a resistor into the =
grounding lead. I built one of these many many years ago, and it lives =
in my toolbox for just this event.
Please note that a discharged CRT can build up a static charge again =
just by sitting on a shelf. Always re-discharge the tube when coming =
back to a tube you've left alone for a while.
Also, Brian's advice about the hand in the pocket is important. Current =
is looking for ground. If your other hand is holding the chassis, then =
the shortest path to ground is across your heart. Not good. =46rom =
your hand down your leg to ground, while not good, is at least not =
across your heart.
It was Dave's advice but I would have stated it if he had not. In college,
a friend and I used to repair TV sets we found placed out for junk colection
and then, we'd sell them for beer money! ;) I took my fair share of shocks.
One discharge was through my thumb and there's still a tell-tale mark there.
--
VAXman- A Bored Certified VMS Kernel Mode Hacker VAXman(at)TMESIS(dot)ORG
Well I speak to machines with the voice of humanity.
On Oct 4, 2013, at 10:56 AM, Cory Smelosky <b4 at gewt.net> wrote:
Yeah. I know they're in the kV range. I'd appropriate discharge the CRT itself...but I lack the appropriate HV grounding wires.
A flat-blade screwdriver and an alligator clip lead. Clip the lead to the shaft of the screwdriver and to the metal chassis of the monitor. Work the flat blade under the rubber cup where the anode wire attaches to the CRT. Be prepared for a loud POP and a flash.
CRT is now discharged.
If the loud pop scares you, then you can build a resistor into the grounding lead. I built one of these many many years ago, and it lives in my toolbox for just this event.
Please note that a discharged CRT can build up a static charge again just by sitting on a shelf. Always re-discharge the tube when coming back to a tube you've left alone for a while.
Also, Brian's advice about the hand in the pocket is important. Current is looking for ground. If your other hand is holding the chassis, then the shortest path to ground is across your heart. Not good. From your hand down your leg to ground, while not good, is at least not across your heart.
Ian
Dave McGuire <mcguire at neurotica.com> writes:
On 10/04/2013 01:47 PM, Brian Schenkenberger, VAXman- wrote:
Does the VT320 have a similar pot for width and height? The width and
height are off on mine.
Inside on the board. Google for the VT320 service guide and it should tell
you the alignment procedure.
Cory, be very careful in there. You are technically astute, and I
know you have a serious knack for this stuff, but there are voltages on
and around that board that are unconditionally lethal.
A finger-to-finger shock will hurt, but a hand-to-hand shock can kill
you. Keep one hand in your pocket or behind your back when the other
hand is inside that chassis. Also, never do this kind of work when
you're the only person in the building.
Sage advice!
Use a non-conducting adjustment tool to trim those pots; not a metal shaft
screwdriver.
--
VAXman- A Bored Certified VMS Kernel Mode Hacker VAXman(at)TMESIS(dot)ORG
Well I speak to machines with the voice of humanity.
yOn Fri, 4 Oct 2013, Dave McGuire wrote:
On 10/04/2013 01:47 PM, Brian Schenkenberger, VAXman- wrote:
Does the VT320 have a similar pot for width and height? The width and
height are off on mine.
Inside on the board. Google for the VT320 service guide and it should tell
you the alignment procedure.
Cory, be very careful in there. You are technically astute, and I
know you have a serious knack for this stuff, but there are voltages on
and around that board that are unconditionally lethal.
Yeah. I know they're in the kV range. I'd appropriate discharge the CRT itself...but I lack the appropriate HV grounding wires.
A finger-to-finger shock will hurt, but a hand-to-hand shock can kill
you. Keep one hand in your pocket or behind your back when the other
hand is inside that chassis. Also, never do this kind of work when
you're the only person in the building.
Very rarely do I even work around low-voltage stuff with two hands. I'll need the appropriate adjustment tool first. I'm not too fond of making my own around HV gear.
-Dave
--
Cory Smelosky
http://gewt.net Personal stuff
http://gimme-sympathy.org Projects
On 10/04/2013 11:23 AM, Lee Gleason wrote:
The terminals themselves were just largish monitors and keyboard
with an LSI11 system built in (an 11/03 or 11/2 - wasn't an 11/23,
they were too new).
Even if you had one now, the magic was in the software that was
downloaded from the TMS system, and the server side stuff that ran on
the host 11. Without a TMS11 system to attach to, it would just be a
bulky LSI11 system with no disk. Now, if you added a disk, and
upgraded the processor, it would be the basis for an interesting
desktop system - but it wouldn't provide the real VT71/72 experience.
Indeed. Then again, the download image would be the big thing -- the
OS support for send/receive of files wouldn't be that big a deal. But
unfortunately the odds of ever finding it would be very slim >indeed;
I think TMS-11 had a total customer base of perhaps 100 sites, maybe a
little more. And I assume those things all shut down quite a long
time ago.
Crazily enough, I looked through my old files and found copies of the
terminal download firmware from my old TSM11 system. On the extremely
remote chance anyone ever finds a VT71, VT72, or VT173 (the VT100 shell
version of this terminal series), let me know and I can provide the .LDA
files that they loaded.
Neat! I recommend getting copies of that stuff to Al Kossow at Bitsavers.
-Dave
--
Dave McGuire, AK4HZ
New Kensington, PA
On 10/04/2013 01:47 PM, Brian Schenkenberger, VAXman- wrote:
Does the VT320 have a similar pot for width and height? The width and
height are off on mine.
Inside on the board. Google for the VT320 service guide and it should tell
you the alignment procedure.
Cory, be very careful in there. You are technically astute, and I
know you have a serious knack for this stuff, but there are voltages on
and around that board that are unconditionally lethal.
A finger-to-finger shock will hurt, but a hand-to-hand shock can kill
you. Keep one hand in your pocket or behind your back when the other
hand is inside that chassis. Also, never do this kind of work when
you're the only person in the building.
-Dave
--
Dave McGuire, AK4HZ
New Kensington, PA
Cory Smelosky <b4 at gewt.net> writes:
On Fri, 4 Oct 2013, Brian Schenkenberger, VAXman- wrote:
Sampsa Laine <sampsa at mac.com> writes:
sampsa <sampsa at mac.com>
mobile +358 40 7208932
On 4 Oct 2013, at 18:34, "Brian Schenkenberger, VAXman-" =
<system at TMESIS.COM> wrote:
Gregg Levine <gregg.drwho8 at gmail.com> writes:
=20
Hello!
Are there any other settings you can tweak? Especially since I
believe that place sitter might be CRT based, so there might be ones
for the contrast and bright. (Remember those? They were found on
classic SDTV sets.)
=20
There should be brightness and contrast controls on the right hand (as =
facing
the display) side of the terminal.
=20
Tried all those, no help.
There is one more on the board. You may need an adjustment tool for it.
It's a small pot near the front and near the brightness and contrast knobs.
Does the VT320 have a similar pot for width and height? The width and
height are off on mine.
Inside on the board. Google for the VT320 service guide and it should tell
you the alignment procedure.
--
VAXman- A Bored Certified VMS Kernel Mode Hacker VAXman(at)TMESIS(dot)ORG
Well I speak to machines with the voice of humanity.
On 10/04/2013 12:31 PM, Cory Smelosky wrote:
Saku Setala donated a VT420 a while back but the screen is almost
unreadable, unless you turn off all ambient light.
Is there any way to fix this?
Increase the current to the electron gun.
The issue here is weak cathode emission. This happens as a CRT ages.
Crap builds up on the oxide coating on the outside of the cathode
impedes its ability to emit electrons. This is generally known as
"cathode poisoning".
There are ways to "rejuvenate" the cathode by applying high-voltage
pulses to it and nearby electrodes like the control grid. There are
devices built to do this. If you find an elderly TV repair person,
he/she will likely have one.
-Dave
--
Dave McGuire, AK4HZ
New Kensington, PA
