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fyndr

Removing analog board from iMac G3

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I am in the process of tearing down my iMac G3 with the purpose of shipping out the motherboard, analog board, and PSU for recapping. I was able to get the motherboard and PSU out after a good deal of effort, and was just starting the final push to remove the analog board. I was able to remove all of the connectors except for the red pair of wires connecting the screen and focus control to the CRT board (shown between my thumb and forefinger in the below imgur album):

 

http://imgur.com/a/bBdN6
 

I can't seem to find any way that these wires can be disconnected from the screen/focus controls, and the controls themselves appear to be soldered directly onto the analog board, so the nearest thing I can tell would be to disconnect the wires from the CRT board itself. Is this the preferred way of removing the analog board from a G3, or is there another alternative? I don't want to pry into the CRT connections if I can help it but will have to do so if there is no other way.

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Every electrolytic capacitor will eventually need to be replaced (link).

But of all seven iMac G3 I own, none needs replacing - maybe in five years time.

I have made a thorough capacitor list for the rev. A and B tray-loading - the list is huge! 57 in both analog and video boards and 11 on the logic board

You can find easy-to-follow disassembly instructions on the Apple Service Source manuals (link).

Edited by goncalo

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So it's a tray-loading (just saw the photos..)

I think you should start with the neck board (I can't remember the name) and remove all cables/connectors.

You'll find a small plastic 'button' you must press to release the red cable.

Then go to the video board (the one you have on its side - where you'll find a lot of connectors!)

And eventually the power source board - be patient with the connector near the base of the crt - you can loosen it from the video board side in case you have already removed it.

Edited by goncalo

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The wires from the focus screen back to the neck board arnt really designed to come out. You have to unplug/remove and ship the neck board with it. Plus theres gonna be a handful of caps on there as well. It contains the video amplifier. 

 

On certain CRT sockets, sometimes there is a release key to allow the wire to come out, but the screen wire is usually soldered into place. 

 

also they DO NOT come out of the flyback! if you pull it out of the flyback, well you need a new flyback! so dont.... 

 

Also the fat red lead which contains the CRT anode cup, you have to squeeze, push it to 1 side and pop it loose from the CRT just like any CRT setup. 

 

Times have changed over the years, early TVs didnt even have an anode cup! they had a simple clip that hooked into the anode button and that was it. all exposed, so they added the silicone anode cup as a safety precaution. 

Edited by techknight

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So to clarify, in order to free the analog board, I will have to open up the metal 'cage' on top of the CRT and remove the neck board which would also need recapping. I've already disconnected the anode and all the other connectors to the analog board so I believe the neck board is the only remaining consideration.

 

Do you know if there is a guide for doing this for the G3 (specifically tray-loading rev B, if that matters) or if there are any particular caveats to removing the neck board? Per the images in the album, I have the unit with the CRT facing down which I think is the correct position for the remaining disassembly. Are any special steps needed to prevent issues with the deflection yoke since it looks like the neck board directly interfaces with that?

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the CRT neck board unplugs off of the rear of the CRT socket like a regular compact classic mac. with the face of the tube laying against a table/cloth/etc.. and the rear of the tube facing you, just pull up itl come off. 

 

Sometimes there is a dab of silicone holding it in place, itll crack loose. 

Edited by techknight

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Sorry, I want to be absolutely clear on what to do before proceeding.

 

The CRT neck board is encased in a metal cage and is connected to the actual CRT assembly. I've taken some pictures from the limited angles that I can to give a sense of how everything's connected.

 

http://imgur.com/a/HH04C

 

In particular, there's what looks like a glass tube with pins in it which ends in a turquoise ring and connects to a beige-colored component (the one with black and red wires attached to it with grey leads) which itself is attacked to the neck board. So if I pull up on the board, it will detach from these pieces without breaking anything? If so, what will remain attached to the CRT and what will remain attached to the board itself? Is the turquoise ring the point at which that connection can be attached/removed?

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That glass tube is what I believe to be the ELECTRON GUN, the thing that shoots off the electrons.

 

I'm not sure, but I believe that if you manage to break that, (even a tiny crack of air in the darkness) you're going to have to salvage a fixed CRT from a working unit...

 

And the process starts again!

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Ah that would be bad. So is there a way to remove the neck board properly without risking fracture? At this rate I may have to ship the entire unit rather than the individual boards for recapping, which is a pain...

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A quick update, I finally had a chance over the weekend to look further into the neck board situation and was able to cross-reference techknight's answer with this guide which is specific to the tray-loading iMac G3 which I have: http://cool-mac.com/imacquarium/other/imac_take_apart.pdf

 

I pulled up on the neck board very carefully but ended up having to exert a decent amount of force to pry it off of the CRT assembly because it was so firmly fitted. So all's well and I can proceed with the recapping effort!

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