[Irinikus]

I managed to purchase a 21" Apple Studio Display (Blueberry - CRT) locally for $133.

I'm willing to go through the process of troubleshooting this unit, as these things are extremely heavy and it would be expensive as well as risky to import one due to its size and weight.

I plan on pairing it with my Max-Spec G3 B&W Tower.

The plastics are in very good condition, but because the display had been sitting in a garage for years collecting dust, it was filthy internally, as it has a huge vent on the top allowing dust to fall freely onto its internal components.

When I picked it up, I took a look through the top vent, and when I saw how much dust was inside, I decided not to attempt to power it up. 

According to the seller, when it's plugged in, it receives power and when you press the power button, you hear a relay click, but there's no picture. So I asked the seller if he heard the classic static sound that these units make as they power up, when he attempted to turn it on. He replied that there was no static sound or static present when he attempter to turn it on.

The Flyback Transformers in these units are known to break down, so from his description I believe that the Flyback Transformer in this unit has more than likely failed.

The good thing is that I did a bit of research before purchasing the unit and found this site: https://crtdatabase.com/crts/apple/apple...20features  which gave me the servicing manual for this unit as well as the serial number for it's Flyback Transformer. Allowing me to track down a replacement part from this site:  https://technotronic-dimensions.3dcartst..._2174.html

Before commencing the troubleshooting procedure, I've decided to tare this unit down completely and give it a thorough clean.

I'll admit that I wasn't prepared for what I'd find on the inside of this unit, although I've always known that they attract dust due to the static they produce, this was crazy!

And so the disassembly of the internal components begins! (Removing the rear plastic cover was more tricky that I thought - it is a bit of a pain in the ass to remove due to all of the tabs which secure it in place.)

It’s important to photograph all of the connections before disassembling! By the way, this is the colour calibration board the Steve bragged about, and although it's the first board you see during the disassembly, it's the last board you can remove from the unit.









Here's an exploded view of all of the sub-assemblies:



The removal of the power module:







The Cleaning Process:





The cleaned Module:



In preparing to remove the main deflection module, so I firstly removed the connections to the electron gun:







The deflection module removal:







The cleaned up deflection module:



Before removing anything else, I took this series of photos to see exactly how the various wiring harnesses need to be routed:



















Finally, a look at the colour calibration board: (You have to remove all of the other modules before you can remove the module which carries this board)



The collection of cleaned parts:



This is as far as I can go with the dismantling for now, as I need a long T-15 screw driver, which I've ordered in, to remove the front bezel. (Which I need to remove before I can remove the intermediate bezel and the base!)



While I wait for my long Torx 15 screw driver to arrive, I've preemptively ordered the replacement Flyback transformer for the deflection board, as I think that this is the most logical place to start in getting this thing back up and running. Considering the fact that these are prone to breaking down and symptoms described by the seller.

[robespierre]

Hi Irinkus,
The fault may not be with the flyback transformer. To have static electricity on the screen, the unit must produce EHT, which uses the flyback. But it depends on the horizontal deflection working also. One of the most failure prone components in a CRT monitor is the horizontal deflection driver, called the horizontal output transistor (HOT).
Since this monitor is a Trinitron, it also has a horizontal convergence block that is suspect. If the HSTAT block has drifted, it can shut down the EHT (it does this to provide X-ray protection).

[Irinikus]

Hi Irinkus,
The fault may not be with the flyback transformer. To have static electricity on the screen, the unit must produce EHT, which uses the flyback. But it depends on the horizontal deflection working also. One of the most failure prone components in a CRT monitor is the horizontal deflection driver, called the horizontal output transistor (HOT).
Since this monitor is a Trinitron, it also has a horizontal convergence block that is suspect. If the HSTAT block has drifted, it can shut down the EHT (it does this to provide X-ray protection).

I ordered a new output transistor along with the flyback. 

even if it’s not a faulty flyback, I still think that it’s prudent to replace it with the replacement that’s apparently far more reliable than the original part.

How do I solve the problem of a possibly drifted HSTAT Block?

[robespierre]

It looks like it may be part of the flyback assembly on your unit.

Code:

Static Conv Electrode
                  o
                  |
                  V
    EHT---------/\/\/\-------\/\/\---+---\/\/\-----+
                                     |             |
                                     o            _|_
                                 Protection      ///

The EHT comes from the flyback; static convergence goes to the tube, "protection" goes to the deflection board.

All trinitrons have this circuit.

[Irinikus]

It looks like it may be part of the flyback assembly on your unit.

Code:

            Static Conv Electrode
                  o
                  |
                  V
    EHT---------/\/\/\-------\/\/\---+---\/\/\-----+
                                     |             |
                                     o            _|_
                                 Protection      ///

The EHT comes from the flyback; static convergence goes to the tube, "protection" goes to the deflection board.

All trinitrons have this circuit.

In TV's this was a red box, but in this setup it looks to be part of the Flyback?

The output Transistor that I ordered is the Fairchild J6810D

In an old Trinitron TV, it's the box on the right with the potentiometer: Sitting between the Flyback and the Anode electrode:



In this monitor there's no such box, but there is a third potentiometer on the Flyback besides the horizontal and vertical focus potentiometers.

---

Thanks for the input, as I have zero experience with CRT's so this will be a good learning experience for me!

[robespierre]

In that picture of the old TV set, the square box unit looks like a voltage tripler. That is a Cockroft-Walton multiplier made of three stages of cross-connected diodes and capacitors.
You will find that—especially on older large sets—where the flyback transformer output isn't high enough. It might also do HSTAT and X-ray protection if that is a Trinitron tube, where the HSTAT electrode is coaxial around the second anode socket, and the red anode cable is also coaxial.

There's a lot to learn about CRTs, so you're in for a great learning experience!
Let us know how you get on, as I can share some ideas, and hopefully other readers as well.

Just a note about cleaning the tube itself: the dark gray color on the bell is a water-based carbon paint called the aquadag. You don't want to clean that too vigorously or use any solvent or it might come off. Just a light wipe with a barely damp cloth is all that's needed. The metal band that surrounds the face of the tube should never be removed, because it provides the integral implosion protection. When you disassemble the bezel, be careful about supporting the tube because you don't want it to fall on its neck, the most fragile part. Keeping it face down on a towel is the best plan.

I can see that you were able to remove the anode cap, which is difficult to do without directions, so you've already shown great aptitude at CRT repair.

An apparently failed flyback can be a case of cracked solder joints, since the flyback is heavy and puts a lot of strain on the circuit board.

See if you get any ideas from these guides:
http://www.repairfaq.org/sam/crtfaq.htm
http://www.repairfaq.org/sam/monfaq.htm

[Irinikus]

Thanks for the links, they're very interesting!

I've already learned something here as I can see two lines across the diamondtron tube in this monitor that I've almost finished restoring







and from this text I now understand why they're there and that they're not a defect:

So What Does It Mean to Have a Trinitron CRT?

Trinitron is a CRT technology developed by Sony. The patent has recently expired and therefore other manufacturers are free to offer similar CRTs. The CRT uses a set of fine vertical wires called an aperture grill instead of a steel shadow mask to separate the R, G, and B electron beams and force them to strike only the appropriate colored phosphors. This in conjunction with an in-line set of electron guns is supposed to provide a brighter image with simpler convergence and purity adjustments. It should be brighter because the percentage of open space of the aperture grill is higher then that of a shadow mask. Other adjustments should be less critical in the vertical direction. In addition, since there is no imposed structure in the vertical direction, undesirable moire patterns caused by scan line pitch compared with the shadow mask dot pitch should be eliminated.
You can recognize a Trinitron tube by the fact that the picture is made up of fine vertical stripes of red, green, and blue rather than dots or slots. The shadow mask in all other kinds of common CRTs are made up of either dots (nearly all good non-Trinitron computer monitors) or slots (many television sets). The Trinitron equivalent is called an aperture grill and is made of around a thousand vertical wires under tension a fraction of an inch behind the glass faceplate with its phosphor stripes.

Since the aperture grill wires run the full height of the tube, there are 1 or 2 stabilizing wires to minimize vibration and distortion of the aperture grill. These may be seen by looking closely 1/3 and/or 2/3 of the way down the tube. The larger size tubes will have 2 while those under 17 inch (I think) will only have a single wire. Many have complained about these or asked if they are defects - no they are apparently needed. You can be sure that Sony would have eliminated them if it were possible.

Another noticeable characteristic of Trinitrons is the nearly cylindrical faceplate. The radius in the vertical direction is very large compared to the horizontal. This is both a requirement and a feature. Since the aperture grill wires are under tension, they cannot follow the curve of the glass as a normal shadow mask may. Therefore, the glass must be flat or nearly flat in the vertical direction. As a selling point, this is also an attractive shape.

In the final analysis, the ultimate image quality on a monitor depends as much on other factors as on the CRT. There are many fine monitors that do not use Trinitrons as well as many not-so-great monitors which do use Trinitron tubes.

Why are There Fine Lines Across My Trinitron Monitor or TV?

These are not a defect - they are a 'feature'. :-)
All Trinitron (or clone) CRTs - tubes that use an aperture grille - require 1, 2, or 3 very fine wires across the screen to stabilize the array of vertical wires in the aperture grille. Without these, the display would be very sensitive to any shock or vibration and result in visible shimmering or rippling. (In fact, even with these stabilizing wires, you can usually see this shimmering if you whack a Trinitron monitor.) The lines you see are the shadows cast by these fine wires.

The number of wires depends on the size of the screen. Below 15" there is usually a single wire; between 15" and 21" there are usually 2 wires; above 21" there may be 3 wires.

Only you can decide if this deficiency is serious enough to avoid the use of a Trinitron based monitor. Some people never get used to the fine lines but many really like the generally high quality of Trinitron based displays and eventually totally ignore them.

Differences between Trinitron and Diamondtron CRTs

(From: Bill Nott (BNott@Bangate.compaq.com).)
Mitsubishi makes the Diamondtron under license from Sony - the subtle differences (according to Mitsubishi) are improvements in the electron gun design for spot uniformity over the CRT face. Also, for the time being, Mitsubishi has tried to introduce Diamondtron tubes in sizes which are not available as Trinitrons - to keep from directly competing, and (ostensibly) to address niches which other sizes can't address.

In order to properly evaluate a monitor, one must consider more than the tube alone - as many readers know, Trinitrons are finding their way into various manufacturer's sets, but they don't all perform the same. In todays market, it's quite possible to find a dot mask design which performs as well as (or better in some cases) the aperture grill design - IMHO every critical monitor purchase should be made by personally examining the monitor to be bought, under the intended application(s).

(BTW, all color tubes use 3 guns, including the Trinitron. Sony used to talk about a "unitized gun", but that only refers to the cathode structure. It's classical use of a misleading term to gain market awareness (looks like it works).)

(From: Someone who wishes to remain anonymous.)

I have found other differences between the Trinitron and Diamondtron tubes. Most noticeable is the grill pitch. The 21" Sony GDM-F520 is 0.22 mm. The 22" Mitsubishi (Cornerstone P1750) is 0.25 mm. For high resolution screens, this makes a difference.

I have also noticed that in a room full of Dell Trinitron monitors, no two monitors have the same color. This is not just a setup issue, the actual tubes have different colors when they are off. The darkness of the black changes.

My gut feeling is that the Dells use a Mitsubishi tube, and that the quality control is not up to Sony's. It is just a feeling, I have not done any research on this.

From what little I know, if you want the very best, you will have to pay for it, (or you get what you pay for).

[robespierre]

The tension wires are barely visible; without being told that they are there, some people notice them and some don't.

The Sony computer monitors also have digital diagnostics that can be accessed with software called DAS or WinDAS. There might be a diag port somewhere on the digital board (the horizontal one under the tube). There are other threads here about that.

[Irinikus]

With this monitor, you can apparently access its diagnostics through the USB hub resident in the monitor, the video board has a link to the USB hub.

[Irinikus]

The tension wires are barely visible; without being told that they are there, some people notice them and some don't.

Being an Audiophile, I've become aware that different people seem to sample the world at different resolutions, and most sample the world at a low resolution.

I unfortunately sample at a very high resolution. (Which means that I'm usually full of shite when it comes to the level of perfection I require!)