Correct Screen Proportions?

[Tempest]

Here's a bit of an odd question. When I first got my compact Mac (a Classic and an SE/30) I noticed that the picture was a bit off center so I opened them up and played with the adjusts until it filled up the entire visible area of the screen. However I've seen on one or two sites that this isn't actually the correct screen proportions and that I need a bit of black space between the actual picture and the edge of the case. My questions are:

1. Is there anything wrong with using the entire viewable area? Will it distort the picture somehow or make things look funny? If it did I haven't noticed so far.

2. If I should have a bit of a boarder, what should the correct measurements be?

 

[mcdermd]

According to the Apple Service Manual:

Size Adjustment
Using the alignment tool, adjust the width control until the raster is 7 inches (177.8 mm) wide.

Using the alignment tool, adjust the height control until the raster is 4.7 inches (119.4 mm) high

 

[Tempest]

That helps. Thank you.

Is there any downside to just maxing out the screen like I already have it?

 

[mcdermd]

Screen distortion in geometry and/or focus.

 

[Tempest]

You know, I though the screen looked a tiny bit fuzzy, I bet that's why. Thanks for the advice.

 

[James1095]

The size is specified such that the DPI of the screen is accurate, making WYSIWYG possible, in other words the size of something on the screen can translate exactly to the size that it will print. As has been mentioned, you might also have trouble getting sharp focus across the entire screen, but if you prefer the whole visible area to be filled it won't damage anything to set it that way.

 

[Tempest]

My main concern was that I didn't want the graphics to be distorted somehow. If it's safe to keep it slightly larger I guess it couldn't hurt (other than the slight fuzziness, but I think there's a focus knob that might help that)

 

[Bunsen]

if you prefer the whole visible area to be filled it won't damage anything to set it that way.

I was under the impression that you ran a slight risk of overstressing aged components with higher deflection voltages. No?

 

[Tempest]

That's probably true since you're asking the monitor to scan more area than it normally would, but we're talking half an inch here and there so it's probably negligible.

 

[onlyonemac]

I've got an Apple Macintosh Colour Display. It's off center, and it's got pincushion, trapeziod, and size errors! (I think it went out due to age.) Three questions:

-What is the correct setting?

-How do I adjust it (there're only position and trapeziod adjuster holes at the back, no size or pincushion)?

-Do I have to use a specially insulated screwdriver to prevent a 10 000V shock in the process?

Thank you.

P.S.

Screen distortion in [...] focus.

Ah! That's why it always looks blurred in places!

 

[Bunsen]

There's an old trick for getting the screen's V to H proportions just right:

Change the desktop pattern to the standard Apple gray - which is actually alternating black & white pixels, diagonally arranged. Then hold something with a known 90˚ corner angle up against the screen - the corner of a floppy disk or a sheet of paper, say - with the corner pointing up, so the two sides slope down 45˚ on either side. You will be able to see quite clearly whether the alternating pixels line up diagonally along the sides of your test object.

 

[James1095]

I was under the impression that you ran a slight risk of overstressing aged components with higher deflection voltages. No?

Technically it does drive the deflection a bit harder, but we're talking a few percent, not nearly enough to cause any problems. Assuming a properly designed monitor, you won't be able to adjust it high enough to damage anything.

You can try adjusting the focus, but it's a static focus control, and you'll probably find that you can make it razor sharp in the center or at the outer edges, but the best focus overall will be a compromise. High end CRT monitors have complex dynamic focus circuits that vary the focus voltage depending on the H and V position of the beam.

 

[trag]

Just in case...

If you find that the display is kind of fuzzy and the focus control has no effect, then you have a burnt out resistor on the analog board. I don't remember which one, but I've seen this symptom enough times, that I think it's worth mentioning. It's an easy fix. It's a pretty common 1/4 watt or similar resistor.

If that turns out to be the problem, report back and I'll try to remember to look it up in one of Pina's books, or someone else might have the information.

 

[mcdermd]

Pina's Dead Mac Scrolls says that if the focus adjustment does not work ...

Symptoms: The display is out of focus. Other than that, the computer is useable.
Typical History: The symptoms appeared out of the blue (not immediately after the computer was board-swapped).

Probable Diagnosis: The problem is on the analog board.

Solution: Check/replace open resistor R9 (1 MΩ, 1/2 watt, 5%).

 

[Scott Baret]

I highly recommend picking up a soft measuring tape if you're going to be adjusting the screen to exact proportions. These are commonly used by two groups of people--tailors and doctors. If you've ever had your waist measured, you've seen this type of tape. I've been using one of these tapes for screen adjustments for almost a decade now and have found it one of the most valuable tools I've ever picked up for compact Mac work, right up there with a long-shafted T-15.

 

[Trash80toHP_Mini]

The paper tape measures at home improvement stores and IKEA are free.

 

[onlyonemac]

There's an old trick for getting the screen's V to H proportions just right:
Change the desktop pattern to the standard Apple gray - which is actually alternating black & white pixels, diagonally arranged. Then hold something with a known 90˚ corner angle up against the screen - the corner of a floppy disk or a sheet of paper, say - with the corner pointing up, so the two sides slope down 45˚ on either side. You will be able to see quite clearly whether the alternating pixels line up diagonally along the sides of your test object.

Thanks, but how do I make sure that it's the correct size, as well as proportions. And what about the other problem with, um..., where're the size adjusters (and pincushion)? And do I have to use an insulated screwdriver to prevent a 10 000V shock?

 

[James1095]

The size adjustments are clearly marked on the cover over the analog board once you remove the back of the computer. You don't need to use an insulated screwdriver, but for the horizontal width you will want to use a plastic tool to adjust the ferrite slug. If you use a metal tool it will not only interfere with the adjustment, but it will get hot as the coil acts like a crude induction heater.

You'd just about have to *try* in order to get a 10kV shock, the EHT is pretty well insulated. The "low" voltage B+ on the monitor board typically packs a much bigger punch, but if you stay on the covered side of the analog board you'll be pretty safe. Just don't touch any exposed connections you see.

 

[Bunsen]

insulated screwdriver

Technically, what you want is a set of plastic adjustment tools, but a well-insulated screwdriver will do. Wooden or plastic disposable chopsticks can also be carved to suit.