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Transplanting 9-inch CRTs - A Journey


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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.

 

 

Edited by jessenator
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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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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...

 

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8 hours ago, Torbar said:

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.

 

8 hours ago, Jinnai said:

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.

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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 :| 

Edited by jessenator
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kcG00Of.jpg?2
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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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.

Edited by jessenator
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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

Edited by Byrd
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12 hours ago, Byrd said:

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.

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17 hours ago, Byrd said:

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!

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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.

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8 hours ago, jessenator said:

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! 

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I've mostly calibrated the green CRT, full album here: https://imgur.com/a/6jpFusD I used the Apple Display Utility available on one of the service CD images.

 

In the time it took me to go through the adjustments the flyback got up to around 95* F. I'm thinking I might see if a 40mm noctua fan might fit between the top of the case and the FBT's cage, just to get some direct flow on it.

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20 hours ago, jessenator said:

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!

 

Just had a look, I'll post pics up another time, but this security CRT is screwed into its bezel using steel clips that attach to a tightly wound wire around the back face of the CRT.  It might be enough to transplant and mount in a Mac.

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Very cool, and thanks for the stls!

 

RE the CRT without tabs: I thought one might be able to spot weld tabs onto the CRT, but then again, you might just cause the CRT to erupt. There's one with tabs on ebay for less last I checked, though.

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