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Scott Baret

The Compact Mac CRT Guide

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To the moderators: Please consider making this a sticky as these questions get asked quite frequently on here.

 

There have been some recent discussions about the CRTs used in compact Macs, specificallly in reguards to compatibility between machines. Having worked inside of dozens of compacts, I became quite familiar with the CRTs used and the variations between the tubes and boards used in the 1984-1993 black and white machines.

 

CRTs IN THE EARLIEST MACS

 

The Macintosh 128K, 512K, Plus, and variations of those machines used the same CRT, which was typically manufactured by Clinton (a Taiwan-based company). Our very own LCGuy has also pointed out that Samsung CRTs exist in these machines as well. It uses Connector Type A (see below).

 

CRTs IN THE MAC SE SERIES

 

The SE, SE/30, and variations of those machines used the same CRT. Many were manufactured by Clinton but Samsung (based in Korea) made a number of CRTs for these machines as well. It uses Connector Type A (see below).

 

ANALOG BOARDS IN MAC CLASSICS

 

The analog board design for the Macintosh Classic changed sometime around the spring of 1991. The original is referred to as Revision A on most parts lists. It used Connector Type A (see below). Sometime around the spring of 1991, Classics began to roll off the assembly line with Revision B boards installed. These persisted throughout the Classic II series and were produced until the demise of the line in 1993.

 

OTHER MAC CLASSIC CRT NOTES

 

Classics manufactured in 1990 should have Revision A boards. The exact time in 1991 when the Revision B board was introduced is unknown, but it seems to have been introduced first in Singapore. I've seen May 1991 Singapore-produced Classics with Revision B yet I've also seen June 1991 Classics from Ireland with Revision A. Any Classic made from later in 1991 or during anytime in 1992 has Revision B. All Classic IIs have Revision B.

 

Of the CRTs with a Type B connector, the vast majority are Clinton-produced. Samsungs are few and far between. I have only seen one personally, in a Classic II, and others have reported seeing maybe only one or two in their Macs as well.

 

The anode caps changed color for all CRTs, not just Samsungs (which had used darker anode caps in the SE series) sometime in late 1991 or early 1992. They are a darker red in the later Classics as opposed to a pale reddish-purple color in the earlier models.

 

CONNECTOR TYPE A vs CONNECTOR TYPE B

 

I term them A and B after the analog boards they are used with. Connector Type A is clear and relatively boxy. It fits itself into another clear plastic connector on the analog board. To remove it, one must hold in on a tab on the side of the connector. Connector Type B, on the other hand, is white and significantly smaller. The connector isn't bulky and is slightly rounded around the edges. It has four holes on its end and fits over four pins.

 

These two display types are NOT INTERCHANGABLE.

 

COMPATIBILITY MATRIX

 

MACHINE        TYPE A     TYPE B
128K/512K        X
Plus             X
SE               X
SE/30            X
Classic          X*         X*
Classic II                  X

 

* Check date of manufacture and/or analog board type inside the case. Most Classics will use Type B unless they are among the first machines produced.

 

CLINTON VS SAMSUNG

 

There is no functional difference between the two, although Samsungs tend to have a different hue of white to them than their Clinton counterparts.

 

WHY THE SWITCH?

 

Apple usually has good reason for changing designs of components. The switch from squirrel cage to rotary fans in the SE is an example of this--those who have been with Macs long enough know of the noise and screen interference problems caused by those fans.

 

In the case of the analog board, I have a few theories. One is that Revision A boards tend to be less reliable, especially in the long run. I've seen more of these with some sort of screen problem (jittering, lines, etc) than of Revision B boards (which seem to be pretty sturdy).

 

Another theory is that Apple wanted to use up older connectors from Pluses and SEs. The SE was actually still in production through the first few weeks of 1991 despite having been formally discontinued (I have an SE with a 1991 date to verify this). They may have been in production to use up older parts. At the same time, Apple was still producing the SE/30. Since the SE/30 was going to be on its way out and replaced by a more cost-effective machine (the Classic II), Apple may have been using up parts like the CRT connectors on the SE with the eventual intent to switch to the newer design, which is believed to have been cheaper.

 

There is also the theory that they switched due to cost reasons but the SE had nothing to do with it. The SE/30 was stlll alive and well in May-June 1991 and was never produced with a Type B connector.

 

CAN I MODIFY A TYPE A FOR A TYPE B BOARD?

 

I've heard it's possible but is supposed to be tricky. Good luck if you try to pull it off. I don't have any directions for this.

 

CAN I SWITCH REVISION A AND REVISION B BOARDS IN CLASSICS?

 

I've swapped dead Revision A boards for working Revision B boards and new CRTs in Classics. Usually I pull from a Classic I'm scrapping for another reason (bad case, no HD, dead logic board, etc). It's often cheaper to just buy a half-dead Classic than to get the parts to make this conversion.

 

As far as Classic IIs go, I've never seen a Revision A board inside one of them. I supposed it may work, but as I said it's never been done, at least not under my eye. If anyone tries it, let me know.

 

WHO OR WHAT IS CLINTON?

 

I wondered this myself when I popped open my first compact Mac. It's obviously not Bill Clinton who owns the company (though our 42nd President indeed was a Mac user). The corporation is Taiwan-based and seems to make a lot of displays for companies and for specialized applications such as closed circuit TVs and hospital monitors. They have a website, punch it into Yahoo to find it. I'm not sure if they still make the 9" for Macs or not.

Edited by Guest

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You may find it interesting to know that my original Macintosh 128k has a Samsung CRT.

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Not a problem...since my Classic II used a Clinton CRT i just assumed that they started out using Samsung CRTs and then switched to Clinton.

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At least you didn't say "Fall" - we don't even have one of them :-)

 

lol That's kinda like here. Instead of Spring, Summer, Fall, and Winter, we have Hot and Humid, REALLY Hot and Humid, Hot, and Less Hot.

 

I never will understand why people like to come down to Florida for the weather...

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Because I don't think you've ever been to Ohio...

 

We have-

GEEZY, It's cooooold, My Finger Fell OFF! Cold, wow, my pipes burst cold, and the patetic, Will it break 50 Today? cold. At least by me, I have a 10,000Sq Mile Lkae in front of me :/ yay Mercury dumping grounds :/

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I have seen several early Macs (128, 512, Plus) that have had their monitors replaced with the green-phosphor unit from the Apple Monitor //c. It's an interesting thing to behold, but it would seem a little tedious to gaze into that much lit green for long.

 

Does anyone know who makes that tube?

 

Here's a few pics of such a unit.

 

 

 

blakespot

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Green was used on early CRTs precisely because it's easier on the eyes than white or another colour.

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One suggestion - "Spring" is at different times of the year in different parts of the world. :-) How about using months instead?

 

Sorry Kallikak, but seasons have a distinct meaning in Apple nomenclature. Example from:

http://docs.info.apple.com/article.html?artnum=19456

 

"The parenthetical product descriptions (Summer 2000) and (Summer 2001) refer to the summer of the Northern Hemisphere."

 

You are, of course, free to create your own Southern Hemisphere terminology ;-)

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A little additional corroboration of the remarks already made about the Classic model M1420, from two of mine:

 

CK1128HBD11—Mar. 1991—Clinton CRT—Type A Analogue board

SG23403RD11—Aug. 1992—Samsung CRT—Type B Analogue board

 

The Singapore example also has a rectangular blanking plate on the case bucket, over a circular port hole to the left of (seen from behind) and slightly below the ADB port. A further distinction between early and later production is the circular pattern of ventilation holes at the front left side of the case (seen from the front) for the speaker. This latter distinction is common to Classic and Classic II, but I cannot yet assert that it corresponds with, say, the analogue board change:

 

SG2010ZAD25—Jan. 1992—no sound vent

SG3207THC2G—Aug. 1992—sound vent

 

Note also, that in defiance of the printed year of manufacture above the serial number, the newer Classic II's serial number begins 'SG3...', indicating 1993. That could be because the first and second digits have been transposed. Re-transposition of the first two digits would better correspond with Aug. (week 30) than does the present week 20 (May) of 1992.

 

de

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It seems to me that the pattern of holes showed up on analog boards sometime in late 1991 or early 1992 around the time the Classic II came out.

 

Apple may have been using up older stock of case backings, sort of like how they made SEs in 1991 to presumably use up parts. The sound vents are found on mid-1992 and later Classics. My guess is that they started putting these in because of complaints that Classics aren't loud enough--put both a Classic and an SE on speaker volume "7" and you'll see what I mean.

 

The new question--was the concept of speaker holes thought of long before it was implemented? Could it be Apple got complaints after the first round of Classic IIs that the stereo sound should sound better from the internal speaker?

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I recall around 1987 or so a company that was offering AMBER replacement screens for the 128, 512, and Mac Plus. I always wanted one. Seemed neat!

 

Anyone know which company it was and whose tube they were using? And is it available today?

 

Thanks!

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Thanks to a posting on vintage computing, I found this excellent forum. One of my vintage machines is a MAC Classic. Because of jittery video, I recently replaced the version A analog card with a version B. I also had to use the yoke assembly that has the correct connector for the rev B analog card.

 

The video looks great now and doesn't jitter.

 

Mike

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AMBER replacement screens/ available today?

 

$19 green or amber 9inch monitors from Timeline Inc.

 

Note that these are NOT drop in replacements for the CRT in a compact Mac. It MAY be possible to swap the CRT and use the Mac's existing analogue board and yoke, or it may not. Using the Timeline monitor's a/b and yoke would probably require extensive mods. Research left as an exercise for the reader.

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Just a tech question regarding the CRT, I notice my small collection of Mac Plus' don't have dag wires - usually a sin. 8-o I've seen piks of US models with dag wire. :?: Is this intentional?

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Since this sticky thread is the "be all guide to CRTs," I would like to ask a very common and related question regarding defective or potentially defective CRTs. People who come to this thread are most likely looking for more than just historical tidbits on vintage Mac CRTs. Indeed many coming here are most likely looking for detailed information on how to test a potentially defective CRT and then how to replace it with something suitable. I therefore would like to pose this question...

 

If a vintage Mac owner has been fiddling around inside their Mac, then bumped something which caused their CRT to flake out (e.g., displaying little more than a white glow at all times), is it safe to remove that CRT and test it in a known good Mac of the same type? And what about CRTs that experienced a heater to cathode short? Would placing potentially defective CRTs and a known good Mac put that known good Mac (analog board and/or digital board) at risk of being damaged by that that CRT?

 

If the known good Mac is at risk of potentially being damaged by bad CRT during testing, then how does one appropriately test a potentially bad vintage Mac CRT?

 

Thank you.

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