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Transplanting 9-inch CRTs - A Journey

jessenator

Well-known member
I've acquired a couple of 9" monochrome CRTs with the intention of transplanting. I've seen it done, but wanted to go through the steps all myself.

I'm starting with a used green-phosphor Matsushita CRT that came out of a CNC machine.

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A little burn-in, but I've got it, so might as well pop it in.

We'll start with hurdle #1 the fitment. 
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As you can see, the original CRT on the left sits lower, so some stand-off construction is in order.

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The overlap is quite awkward...

The first run of the stand-offs. The dimensions were almost 100%. I decided not to print the full height for this test

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They fit like a glove though :)  

I decided that since the clearance is so tight, the screws that mount this CRT to the stand-off pieces will go in at an angle, pointing inward.
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So I'll need two separate models, basically a mirrored version of the one. Hopefully I'll have enough sleep tonight I'll be able to fill the gaps. I'll keep updating as I go along.

Edit: I'll also need to lop off a bit of the circle section to make room for the analog board.

 
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jessenator

Well-known member
R2 of the stand-off (variant A anyway) is ready to go. This one is more of a proof to see if I can adequately secure the CRT to the standoff. 

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The magenta screw is the OEM one that mounts the CRT to the case, so I had to account for its space when contemplating the sort of diagonal pilot holes for the other screws I have to mount the screen to the stand-offs.

So we'll see how this all works once it's printed. Hopefully there's enough clearance.

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jessenator

Well-known member
A little refinement was required, but r3 seems to """""work""""" on the dry run in the Classic chassis

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The fit isn't flush by Apple standards, but it should get the job done. I'll feel better when I have all 4 in there (and printed in nylon), now to build the not-quite-mirrored stand-off...

 

maceffects

Well-known member
Have you considered swapping the strap/frame?  I don't see a reason why they wouldn't interchange from the picture. 

 

Jinnai

Well-known member
could I possibly get a copy of the stl for the adapters? I had the same problem with a CRT I tried to put in, but don't have 3D modeling skills to make an adapter..,

 

jessenator

Well-known member
in another thread a few people said that it could cause the CRT to implode
This ;)  

When I was looking at the close-ups of the amber CRT (Nickpunt's photos) that's on the way, the band appears to have a screw to keep it in place, but there's a secondary band to clamp the RF shield(?) for the IBM 5155 part assembly (analog board etc all hooked up). The actual band around the tube looks to be crimped on there :/  I don't want to attempt it, really, unless someone can conclusively state that there's no implosion danger.

could I possibly get a copy of the stl for the adapters?
Certainly :)  however, they are kinda bodgy IMHO. This has really messed with my brain (having had no industrial design/engineering training), but I'll share them as soon as I verify the opposite side is working as well.

 

jessenator

Well-known member
One small update I was having adhesion issues so I paused (rather than exploded at) the printer, so I'm printing those stand-offs today.

Additionally, one thing, relative to this post about the 5155 amber CRTs, is that this green Matsushita CRT is oriented just like the Macintosh monitors (or rather, the neck tube pins are), so no need for neck board wiring extensions or flipping the anode cup side with this one, so that's a plus against its many minuses :lol:  The amber one will need an extension solution for the neck board (or placing the anode cap on the AB side of the Mac, which I'm personally not terribly fond of doing).

Hopefully once these stand-offs are done I can get this mounted into the SE/30 without much issue :| 

 
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jessenator

Well-known member
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Got cold feet and opted to wait till I have some gentle and non-conductive tools to adjust the yoke, et. al. so It's ready to be transplanted. Additionally, I finalized the opposite corner mounts.

@Jinnai hopefully these work for your situation. I will say, there is some play with the rotation (I didn't quite get the semicircle inset perfect), so you might have to hold the stand-offs with some pliers as you screw in the CRT screws. Speaking of, the screws I'm using are 3.94mm (measured at the threads outermost diameter) versus the 4.25mm of the Apple OE T15 screws, so even though that makes them, more or less, an M4 screw, I'd err on the side of short-of-4-mm vs over.
STL files named "A" and "B": https://www.dropbox.com/sh/78wweaws88wl68d/AACfMlXJhTe0YynXWw7KO88Ja?dl=0

I'd recommend against printing supports, as they can be a real beast to extricate and it doesn't deform that section of the model very much, TBH—not that detrimental to the overall pieces.

If you're looking at the CRT from the back (i.e. with the case open, preparing to remove it from the mounts).

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jessenator

Well-known member
Well one thing on the dress rehearsal I'm discovering is the chassis on the SE/30 (presumably the SE) is a bit bulkier than on the Classic. Oops. 

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I know it's completely incidental, but part of my brain can't help but think... "they made this frame an extra 5-10mm taller on purpose because they knew... they knew" :lol:  

Guess some sanding is in order. I could print others with that chunk removed... But at any rate, this effects the bottom stand-offs, as the chassis spans the whole width.

 
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jessenator

Well-known member
Alright, so I think this is pretty dang on, so I've uploaded these STLs into that same directory. The other added benefit is that the chassis will hold these in place
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It's getting close!

 

Byrd

Well-known member
Great progress, jessenator, I appreciate your attention to detail!

Hopefully not going off topic here, but today I found what appears to be an never used 9" monochrome security monitor with a Samsung 240AG4A CRT - I presume I'll be going through a similar process here should I decide to replace one of my burnt in Plus/SE/Classic CRTs?

It's the same CRT as this:

https://www.ebay.com/itm/Samsung-CRT-Monitor-Picture-Tube-Type-240AG4A-/184185290924

 
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Daniël

Well-known member
Great progress, jessenator, I appreciate your attention to detail!

Hopefully not going off topic here, but today I found what appears to be an never used 9" monochrome security monitor with a Samsung 240AG4A CRT - I presume I'll be going through a similar process here should I decide to replace one of my burnt in Plus/SE/Classic CRTs?

It's the same CRT as this:

https://www.ebay.com/itm/Samsung-CRT-Monitor-Picture-Tube-Type-240AG4A-/184185290924


If the one you found has no mounting "ears" like the one in the eBay ad, you'll definitely have to manufacture something to hold it in place.

 

jessenator

Well-known member
I presume I'll be going through a similar process here should I decide to replace one of my burnt in Plus/SE/Classic CRTs?
Yes, I think the word is that these 9" monochrome CRTs all have a similar connector on the neck. And like Daniel mentioned, if yours doesn't have the metal ears, you'll have to get creative on how you mount it into yours into the case. 

I imagine it would need to be a second, custom metal band around the outside and secured with a worm-screw type mechanism at the top. If yours does have ears, I'd measure the ears' holes vs the OEM like I did to see how much play there is, etc. Good luck!

 

jessenator

Well-known member
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It's green-ish :) but nowhere near as emerald as a //c or other green CRTs I've seen.
 

Also, some things on power-up that I'm not terribly sure are normal: 




 

jessenator

Well-known member
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Tonight!

And @nickpunt wasn't lying, that new old electronics smell was right there out of the bag. Also, do you have any pointers for efficiently removing that assembly cage?

I think as far as that green CRT is concerned, the main issue is whether or not the tube itself is within spec (pulling too much for the board, or the board is supplying too much) to the point where, yeah, it works, but I'd rather not have to put a flyback transformer on my list of purchases for the next long while.

 

nickpunt

Well-known member
Also, do you have any pointers for efficiently removing that assembly cage?
Socket wrench was all I needed, looked more difficult than it was. The yoke was a bit of a pain just because it’s fragile and lots of wires were around limiting movement. There’s goo around the anode so wear gloves! 

 

jessenator

Well-known member
Ah, so you left all the original wiring intact. I suppose it could be a nice windfall if a 5155 owner needed a new assembly, but not a CRT.

 
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