28 Jun
2006
28 Jun
'06
6:14 p.m.
I've just got hold of an old (probably late-80s) Hughes 800 projector.
It's a couple of feet long and very very heavy. Inside is a big xenon
lamp, a CRT of some kind, and some optics. It appears to work by
shining the lamp (through mirrors) onto the face of the CRT. The big
problem is, it doesn't appear to produce any video. I can hear the CRT
scan coils going. The scan pitch changes when I remove the video
source. In fact, it does appear to do all the things I'd expect when I
press buttons, but no picture comes out :-/
There is (getting vaguely on-topic) an RS-232 port and it appears to use
a TMS9900 CPU inside.
Anybody got any idea how it even works? Even better, has anyone got an
idea how to make it work *properly*?
Gordon.
29 Jun
29 Jun
3:24 a.m.
Gordon JC Pearce wrote:
I've just got hold of an old (probably late-80s)
Hughes 800 projector.
It's a couple of feet long and very very heavy. Inside is a big xenon
lamp, a CRT of some kind, and some optics.
I dont know of any way that shining light on a CRT would produce joy,
because
the CRT will emit light. If it is not a CRT but is a device that works
by tranmission
from a white light source, it would not be making the
noise, or have
sweep circuits,
but it would also be possible that it was working and be difficult to see.
I had a GE theatre size projector which had an integrated CRT. It used
such high voltage to zap phosphor that it was an Xray hazzard, and in and
of itself had become radioactive from long operation (it was 25 to 30
years old when I got it). It had a 12" diameter schmidt corrector and a 15
or so inch diameter primary, and was a rearward projecting Schmitt / Cass
optical system.
I assume your system is reflective, with the lamp optically shining on the
CRT, or do you think it is tramsissive, thru the CRT tube?
so about all I can help with here with the post is to suggest you dont have
prolonged exposure to it till you can assess it's radiation status, and keep
women and children away totally till you know.
Jim
6:11 a.m.
jim stephens wrote:
so about all I can help with here with the post is to
suggest you dont have
prolonged exposure to it till you can assess it's radiation status, and
keep women and children away totally till you know.
ISTR that Gordon's a Citroen fan, and so a lost cause anyway ;-) *runs*
On a serious note, is the filament to the tube glowing, suggesting that it's
getting HV? (you'll almost certainly have to disable that xenon lamp to tell!)
Failing that - how about the obvious - brightness control, or small
board-mounted brightness trimmer that may have broken or have worn contacts?
cheers
Jules
28 Jun
28 Jun
8:49 p.m.
jim stephens wrote:
What's wrong with Citroens? If I ever learn to operate such a machine, a
DS is very high up my list of 'wants' :-)
Mind you, I spent a good many years as a particle physicist, so
presumably got a bit of stray radiation....
so about all I can help with here with the post
is to suggest you dont have
prolonged exposure to it till you can assess it's radiation status, and
keep women and children away totally till you know.
ISTR that Gordon's a Citroen fan, and so a lost cause anyway ;-) *runs* On a serious note, is the filament to the tube
glowing, suggesting that it's
getting HV? (you'll almost certainly have to disable that xenon lamp to tell!)
It's not always the case that the filament supply comes from the line
output transformer. I'd suggest measuring as many of the electrode
voltages as you can (including the EHT if you have a suitable probe, and
to be honest, if you're working on CRT stuff, you need one).
-tony
29 Jun
29 Jun
11:56 a.m.
On Thursday 29 June 2006 03:24, jim stephens wrote:
I had a GE theatre size projector which had an
integrated CRT. It
used such high voltage to zap phosphor that it was an Xray hazzard,
and in and of itself had become radioactive from long operation (it
was 25 to 30 years old when I got it).
As has been said here before, it is NOT possible to make things become
radioactive from shooting x-rays at them. It's not even a problem in
laboratory x-ray environments, let alone the small amount that could be
put off from a CRT.
If it's radioactive when it's off, it's from another source.
Pat
--
Purdue University ITAP/RCAC --- http://www.rcac.purdue.edu
The Computer Refuge --- http://computer-refuge.org
1:40 p.m.
I had a GE
theatre size projector which had an integrated CRT. It
used such high voltage to zap phosphor that it was an Xray hazzard,
and in and of itself had become radioactive from long operation
As has been said
here before, it is NOT possible to make things
become radioactive from shooting x-rays at them. 
2:02 p.m.
der Mouse wrote:
That's not what's claimed.
What's claimed is that shooting electrons at the screen fast enough
both (a) generated X-rays, and (b) rendered that screen radioactive.
This has nothing to do with whether X-rays can make what they hit
radioactive.
Anyway, if an electron beam can cause something to be radioactive, then
X-rays can too, by using the photoelectric effect to generate an
electron beam within the material, no?
Peace... Sridhar
I had a GE theatre size projector which had an
integrated CRT. It
used such high voltage to zap phosphor that it was an Xray hazzard,
and in and of itself had become radioactive from long operation
As has been said
here before, it is NOT possible to make things
become radioactive from shooting x-rays at them.
2:30 p.m.
What's
claimed is that shooting electrons at the screen fast enough
both (a) generated X-rays, and (b) rendered that screen radioactive.
This has nothing to do with whether X-rays can make what they hit
radioactive.
Anyway, if an electron beam can cause something to be radioactive,
then X-rays can too, by using the photoelectric effect to generate an
electron beam within the material, no? 
4:12 p.m.
On Wednesday 28 June 2006 06:14 pm, Gordon JC Pearce wrote:
I've just got hold of an old (probably late-80s)
Hughes 800 projector.
It's a couple of feet long and very very heavy. Inside is a big xenon
lamp, a CRT of some kind, and some optics. It appears to work by
shining the lamp (through mirrors) onto the face of the CRT. The big
problem is, it doesn't appear to produce any video. I can hear the CRT
scan coils going. The scan pitch changes when I remove the video
source. In fact, it does appear to do all the things I'd expect when I
press buttons, but no picture comes out :-/
Is there a number anywhere visible on that "CRT"? It may not be one,
possibly...
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, a critter that can
be killed but can't be tamed. --Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin
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8 comments
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participants (8)
-
ard＠p850ug1.demon.co.uk -
gordon＠gjcp.net -
julesrichardsonuk＠yahoo.co.uk -
jwstephens＠msm.umr.edu -
mouse＠Rodents.Montreal.QC.CA -
pat＠computer-refuge.org -
ploopster＠gmail.com -
rtellason＠verizon.net