17" CRT - Worth Keeping?

Tony Duell ard at p850ug1.demon.co.uk
Wed Jul 21 15:06:13 CDT 2010

> =0A=0A--- On Tue, 7/20/10, Tony Duell <ard at p850ug1.demon.co.uk> wrote:=0A=
> =0A> 
>=A0 I got beat (or rather just=0A> beat myself) out of a beautiful co=
> lor NCR =0A> > PC4. Most people would say big deal, but I wanted the=0A> da=
> mned thing! Just =0A
> =0A
> THis is not a machine I am familiar with
.=0A=0A =
> Think of a color Lisa w/a DOS prompt! LOL LOL LOL LOL=0A =0A

That sounds impossible. The Lisa as a 68K machine, and AFAIK MS-DOS (I 
assume that's the 'DOS' you are refering to) ran on the 80x86 only.

> > Now that is somethign that I would never do. I always want=0A
> > to keep a classic=0A> machine as close to the origianl design as possible. 

> I like to think of it as a value added rework ;) 

Hmmm... I really do like to keep the electronics as it was designed to 
be./ That's what defines the machine to me. If you mount a PC motherboard 
in (say) a PERQ chassis, the result is a PC, not a PERQ. And when I was 
repairing my HP9835CU, I had the motherboard sitting on top of the 
monitor case, other PCBs plugged in, the PSU input running off my bench 
supply, the disk drives sitting on top of said bench supply, etc. It 
didn't look like an HP9000 machine, but IMHO it was. It was running the 
HP9000 software.

> As to the rest of your <snipped>, Tony, you're an invaluable asset to 
> the hobby, and an inspiration. I *can* imagine winding a transformer, 

Waht's that got to do with anything>

> but blowing a tube - although it has crossed my=
>  mind - eh, it just ain't happening. So I look for workable

I don't believe I suggestedyou amde your own CRT. Having made a very poor 
CRT [1] at school in one of the things I did when others were booting balls 
around, I can understnad why you'd not want to do it. It is very hard.

[1] Glass bell jar with a rubber bung in the top with 4 wires going 
thorugh it. 2 carried defleciton plates (just one axis, I was just 
proving it could be done) made from aluminium foil. The other 2 carried a 
michrome filament (I didn't have any tungsten). Metal base plate of the 
bell jar covered in ZnS. Whole thing continuously pumped by a rotary pump 
(not a hard enough vacuum, but it's all I had). Filament run from a 
lead-acid cell sitting on a glass-legged stool to insulate if from 
ground. HV inductuon coil between one side of the filament and metal 
base/'screen' to povide an acceleerating voltage. Yes, I got a spot on 
the ZnS. And yes I could deflect it witha permanent magnet outside the 
bell jar, or using the defleciton plates (a few hundred V IIRC).

> alternatives. Anything to keep the bugger working. My sister has a 

I would replace the CRT, using something electrically similar. Even if I 
had to strip it from an old monitor. I would not replace the PCBs, though.


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