Delta Gun Hype/understanding

[compu_85]

I can still feel a tinge in my back from moving those large Sun branded Sony monitors :S

[ppppenguin]

Back around 1984 I was working on 1024*1024 32 bit graphics systems. This was really exotic back then with cages full of massive cards and hefty 5V PSUs.

The company was using delta gun CRT monitors with these brutes. ISTR they were Mitsubishi. It was exceedingly difficult to get these monitors purity and convergence good enough for the high end graphic arts stuff we were doing. Nightmare would be a good desciption. They said they had tried an inline gun monitor but it wasn't good enough.

Apart from re-designing the graphics generators to lower the cost, my job was to evaluate the latest monitors and prove they were up to the job. I settled on a Barco high resolution jobbie with inline guns. Can't remember if it had dots or stripes. Purity and convergence were a doddle, generally OK out of the box. All I had to do was convince the picky arty types that they were at least as good as the delta gun monitors. It was blatant to anyone that they were good, the only weakness was that the absolute resolution was a fraction worse than the delta guns.

The production and test people were grateful for the change. Basically if the new monitor looked right, then it was right. No more finicky purity measuements with a colour analyser and seeing if the result was within tolerance.

[Yamamaya42]

Since this thread is about the delta-gun types, there is something that I have always wondered, which was / is the better CRT from a technical / longevity standpoint?
The roundies or the rectangular types?
Granted, you lose a small % of the pic with the roundies, but I don't even think it was really noticed much in it's day.

[Yamamaya42]

Originally Posted by ppppenguin

Back around 1984 I was working on 1024*1024 32 bit graphics systems. This was really exotic back then with cages full of massive cards and hefty 5V PSUs.

The company was using delta gun CRT monitors with these brutes. ISTR they were Mitsubishi. It was exceedingly difficult to get these monitors purity and convergence good enough for the high end graphic arts stuff we were doing. Nightmare would be a good desciption. They said they had tried an inline gun monitor but it wasn't good enough.

Apart from re-designing the graphics generators to lower the cost, my job was to evaluate the latest monitors and prove they were up to the job. I settled on a Barco high resolution jobbie with inline guns. Can't remember if it had dots or stripes. Purity and convergence were a doddle, generally OK out of the box. All I had to do was convince the picky arty types that they were at least as good as the delta gun monitors. It was blatant to anyone that they were good, the only weakness was that the absolute resolution was a fraction worse than the delta guns.

The production and test people were grateful for the change. Basically if the new monitor looked right, then it was right. No more finicky purity measuements with a colour analyser and seeing if the result was within tolerance.

1024x1024 32 bit? in 84?? had no idea they had that back then...

in 84, i was a very VERY young kid, playing games in 320×200 in 16 colors, on my dad's ibm 5150

[Tom9589]

Compu 85, did Sun build those monitors or did Sony build them and slap a Sun nameplate on them? I had the back off once and there was a ton of electronics in there! No wonder they were heavy. We had a company rule that it required two folks to move one.

[trinescope]

Originally Posted by Yamamaya42

Since this thread is about the delta-gun types, there is something that I have always wondered, which was / is the better CRT from a technical / longevity standpoint?
The roundies or the rectangular types?
Granted, you lose a small % of the pic with the roundies, but I don't even think it was really noticed much in it's day.

I'm pretty sure the round CRT shape with the spherical faceplate was used because it has lesser demands on the electronics and the CRT hardware for purity, convergence, and pincushion distortion. When Motorola started making sets with the first modern rectangular tube, the 23EGP22, they had to include extra circuitry for pincushion correction. I'm sure there were changes to the convergence circuits as well since this CRT had a flatter faceplate than the 21" round tubes.

As far as longevity goes, that's more a matter of materials, manufacturing, and end usage by the customer than the shape of the CRT. I would say that on average the later CRTs should hold up better since they had more efficient phosphors and therefore didn't need to run the electron guns as hard.

[Electronic M]

Originally Posted by Yamamaya42

Since this thread is about the delta-gun types, there is something that I have always wondered, which was / is the better CRT from a technical / longevity standpoint?
The roundies or the rectangular types?
Granted, you lose a small % of the pic with the roundies, but I don't even think it was really noticed much in it's day.

Longevity huh? If it's shelf life they are probably all comparable. If it is power it up for as many hours as it takes to burn the cathode off the gun Zenith Delta gun rectangular sets from 1970-78 (chromacolor black matrix era) probably take the prize. The CCII chassis that drove them were nearly immortal too. Some of those sets were found by fire fighters after house fires with the plastic melted and speaker cones burned out still showing a perfect picture under the soot stuck to the screen. Many still work as found today and some of those were in continuous service since new.

[old_tv_nut]

Originally Posted by trinescope

... When Motorola started making sets with the first modern rectangular tube, the 23EGP22, they had to include extra circuitry for pincushion correction. I'm sure there were changes to the convergence circuits as well since this CRT had a flatter faceplate than the 21" round tubes...

Correct. Rectangular sets required at least third harmonic horizontal-rate dynamic waveforms in addition to the sawtooth and parabola of the roundies. This adjusted the convergence midway between screen center and the left and right edges.

[old_tv_nut]

By the way, the 23EGP22 screen aspect ratio was narrow - 1.27:1 instead of 1.33:1 (4x3). This allowed a longer horizontal retrace time without producing black bars left and right or making people look fat, which in turn reduced the peak retrace voltage on the horizontal output device. It was barely possible to produce reliable horizontal output transistors (with the required "safe area" of voltage and current), so every little bit helped.

[ppppenguin]

Originally Posted by Yamamaya42

1024x1024 32 bit? in 84?? had no idea they had that back then...

in 84, i was a very VERY young kid, playing games in 320×200 in 16 colors, on my dad's ibm 5150

Only in VERY expensive professional kit. Think $250,000+ range. The hard discs were removeable packs sitting on drives the size of a washing machine. The computing power was bit slice processors for the graphics manipulation backed up by some kind of PDP11.

A few years later you could run photoshop on affordable kit.