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Garrett

Removing the analog board/CRT neck board

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Ever since I received and installed my freshly-recapped logic board for my 1991 Macintosh Classic, the machine has been reliable and working wonderfully. (Besides the 1-2 minute delays on startup, where it displays a pattern on the screen. It supposedly is something related to the ROM.) I should say the machine was working great... until tonight.

 

One of my fears was finally realized: the analog board is obviously going to need to be recapped soon. (Although I knew it was going to happen at some point, I was going to procrastinate on it.) Upon starting the machine tonight, it took a couple seconds for the display to come up. When it did, the image appeared to "wave" around the screen. When the machine chimed, it gave me a flashing question mark icon. The hard drive wasn't spinning.

 

After rebooting the computer, the hard drive spun up and everything was good. However, I noticed some pincushioning on both sides of the screen. After about 1-2 minutes of the computer being on the pincushioning went away and the machine ran perfectly fine.

 

So my question is: how difficult is it to remove and re-install the analog board? Specifically, I'm worried about the CRT and the neck board. The CRT on this machine is fairly crisp, so the last thing I want to do is to accidentally ruin it by breaking the neck or the tube itself.

 

Any input would be greatly appreciated.

IMG_7364.JPG

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For me, it’s just a matter of minutes. 

 

If you never had done it before, the tricky moment is removing the suction cap. 

 

The board and neck board are easy to remove with just one or two screws for the AB and nothing for the neck one. 

Edited by bibilit

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Thanks. I'll find a video on the suction cap... I've seen some 8-bit Guy videos where does it but it's been a while. I'm mostly concerned about the neck board, given that the neck is the weakest part of the tube and thus the most prone to breaking.

 

I recall seeing what appears to be hot glue around the area the neck board connects to the tube. Would I need to do anything with that prior to attempting to remove the board?

 

Also,  how much force does it take to remove the neck board? This computer (as far as I know) has never been serviced before I purchased it, so it's likely the neck board has never been removed from the CRT since the computer was manufactured.

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Just pull the video board gently towards the rear side of the Mac and maybe do a tiny bit of side wiggling while pulling in order to pull it in several little "mini" steps.

In fact I remove it as a habbit almost every time I do something in the HDD- and floppy drive connector cable area.

I have a kind of trauma, because I broke the neck of one of these precious old 9" crts once, when I was so caught in pushing the SCSI cable into the logicboard socket, that I did not realize that my forearm put some sidewards pressure on the video board.

Sometimes I still wake up in the middle of the night, hearing the hissing noise of the lost vacuum...

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17 hours ago, dochilli said:

Discharge the CRT before you work at the AB!

I already know to discharge it at the anode cap. I've heard most CRTs from this era (should say the driving circuitry) are pretty good about discharging the CRT itself, but never a good idea to rely on that.

11 hours ago, Bendix said:

Just pull the video board gently towards the rear side of the Mac and maybe do a tiny bit of side wiggling while pulling in order to pull it in several little "mini" steps.

In fact I remove it as a habbit almost every time I do something in the HDD- and floppy drive connector cable area.

I have a kind of trauma, because I broke the neck of one of these precious old 9" crts once, when I was so caught in pushing the SCSI cable into the logicboard socket, that I did not realize that my forearm put some sidewards pressure on the video board.

Sometimes I still wake up in the middle of the night, hearing the hissing noise of the lost vacuum...

When reinstalling the logic board in this machine, I was careful to keep my hands in the bottom part of the machine. The biggest problem for me is plugging in the molex plug coming from the analog board... sometimes I have to put a little bit of force on it to get it to snap into place properly, which makes me worry whether I'm putting too much force on the connector/board. As for the floppy/hard drive connectors, I've found that I can pull the logic board out and feed the cables through the bottom of the frame. Usually there's just enough slack in there that I can plug them in and slide the logic board back into its proper place. But, of course, the Classic has a smaller logic board and is built different from the earlier models.

 

That sucks about accidentally breaking the neck. That would be my worst nightmare... accidentally breaking the neck and hearing the hissing. :`(  These old Macs are extremely rare around here (at least for a decent price) so it took a couple years just to find this one. Plus, its CRT is in really good condition. It appears to have been a low-hours machine.

11 hours ago, bibilit said:

don't forget to remove the tiny cable going to the fan and the big one to the CRT

Will do. I'm assuming the big cable going to the CRT is the high-voltage one that goes to the anode cap? Also, isn't there a ground screw on one of the CRT mounts that must be removed?

 

Thanks everyone for your replies. This is making me extremely nervous, because I'm afraid I may use a little too much force or may accidentally jostle something wrong and snap! hiss! It might be a while before I'm able to actually get the analog board recapped.

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When pushing those molex connectors back into the analog board, a good idea is to put opposite pressure from the other side of the board. This keeps the board stiff and it doesn't bend away from you when you press the connector into the socket. This makes it a lot easier to not use so much force from one side.

 

Also, the anode cap is not hard to remove at all. As long as you have discharged it (as you stated you will), you can then get long, thin needle nose pliers under there, pinch together the metal fingers that are holding it in place, and lift up. The biggest benefit to the Mac ones is they are clear, and you can somewhat see what is going on under there.

Edited by LaPorta

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8 hours ago, LaPorta said:

When pushing those molex connectors back into the analog board, a good idea is to put opposite pressure from the other side of the board. This keeps the board stiff and it doesn't bend away from you when you press the connector into the socket. This makes it a lot easier to not use so much force from one side.

 

Also, the anode cap is not hard to remove at all. As long as you have discharged it (as you stated you will), you can then get long, thin needle nose pliers under there, pinch together the metal fingers that are holding it in place, and lift up. The biggest benefit to the Mac ones is they are clear, and you can somewhat see what is going on under there.

Thanks for the tip on the logic board molex connector. However, I normally have the computer set normally when I reinstall the logic board, so I can't really put my hand below the logic board.

 

As for the anode cap, I always thought you could simply squeeze the fingers holding it in place from the outside. Guess I was wrong, though.

 

Tried powering up the Classic today and it was acting up again. I was able to get it to a flashing question mark icon :?:... hard drive doesn't seem to spin up. (I'm assuming it isn't getting the proper voltage.) On a couple of tries the machine chimed multiple times, one try it chimed probably 5-6 times. Also noticed the pattern slowly goes away. Unlike last night, I couldn't get it past the flashing question mark icon.

 

Guess I'm going to have to have the analog board recapped. :cry: I knew it was just a matter of time though... I've heard that the Classic/Classic II are notorious for having bad caps, although any old computer isn't immune.

 

I have a video of the behavior, but it's shaky.

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8 hours ago, Garrett said:

As for the anode cap, I always thought you could simply squeeze the fingers holding it in place from the outside. Guess I was wrong, though.

I think that's a much better way to do it.  Trying to squeeze in plyers (needlenose or otherwise) would make it easy to scratch the coating on the CRT.  I've never met an anode cap that didn't come off very easily - what I do is lift up the sides to see what direction the prongs are facing.  I then hold the back of the anode cap and shift it to one side to compress the prongs and release one side and then tilt to get the one side out then you can just slide it off.  No fuss and no tools.

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8 hours ago, Garrett said:

Thanks for the tip on the logic board molex connector. However, I normally have the computer set normally when I reinstall the logic board, so I can't really put my hand below the logic board.

 

As for the anode cap, I always thought you could simply squeeze the fingers holding it in place from the outside. Guess I was wrong, though.

Yes, but I have found, for the logic board, that pushing down away from the neck of the tube is not a big deal. When you are pushing directly past and underneath it for the analog board, that is where it gets tricky...

 

You can squeeze with your fingers, but I have always had more consistent luck with the pliers personally.

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11 hours ago, superjer2000 said:

I think that's a much better way to do it.  Trying to squeeze in plyers (needlenose or otherwise) would make it easy to scratch the coating on the CRT.  I've never met an anode cap that didn't come off very easily - what I do is lift up the sides to see what direction the prongs are facing.  I then hold the back of the anode cap and shift it to one side to compress the prongs and release one side and then tilt to get the one side out then you can just slide it off.  No fuss and no tools.

Maybe I just do it wrong!

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10 hours ago, LaPorta said:

Maybe I just do it wrong!

Sorry if that came across as rude...  editing on a phone isn't always that fluid.  I do think that keeping sharp or scratchy tools away from your crt is best thought and it's usually pretty easy to manipulate the cap off with just your hands using the technique I noted. 

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I will try to remove the anode cap by hand once I can cobble together a tool to discharge the CRT. An flathead screwdriver (with an insulated handle) and an alligator clip running from the screwdriver to the metal chassis should be sufficient to discharge the CRT, correct? (That's what I've seen in almost every video showing someone discharging a CRT.) I'm assuming it's crucial to remove the logic board from the computer before doing any work on the CRT.

 

As mentioned, I'm mainly worried about the neck board and reinstalling everything. Last thing I want to do is either break the neck of the CRT or reinstall something wrong and let the magic smoke out of something else or, worse, catch something on fire. :eek:

 

As for now, I've made a video depicting the behavior this machine is currently going through. I was able to get it to boot into the ROM operating system, but it instantly crashed as soon as I loaded a floppy disk. When it came back up, it went into a "chime cycle" where the machine would crash (thus chiming again) when trying to eject the floppy. I ended up having to manually remove the floppy using a straightened paper clip.

 

Here's the video: 

 

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12 hours ago, Garrett said:

An flathead screwdriver (with an insulated handle) and an alligator clip running from the screwdriver to the metal chassis should be sufficient to discharge the CRT, correct? (That's what I've seen in almost every video showing someone discharging a CRT.)

 

I always connect the flathead screwdriver with a jumper cable to the heater near the thermostat, where there is a spot without paint and just bare metal. I hope, that is ok, too? 

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DId you check the voltages at the floppy port? I think that leaky caps on the AB cause the reboot of the classic. The voltages are not stable and the classic resets. So you should do a recap of the AB but also a recap of the LB!

 

Edited by dochilli

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That would make sense. The motor on the floppy drive would need a big increase in power to drive it and could cause that crash.

 

As for discharge, that should work. If you plan on discharging a lot of machines, you could make one that goes straight to outlet ground, which I did.

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8 hours ago, dochilli said:

DId you check the voltages at the floppy port? I think that leaky caps on the AB cause the reboot of the classic. The voltages are not stable and the classic resets. So you should do a recap of the AB but also a recap of the LB!

 

That was precisely my speculation, but unfortunately I don't have a multimeter to test any voltages on this machine. My guess is that there simply isn't enough voltage for the hard drive to spin up. When I boot into the ROM operating system and insert a floppy, the drive's current brings down the voltage and crashes the machine. Then, as the machine tries to eject the floppies on boot, it brings down the voltages again causing the machine to reset, rinse and repeat until you break the cycle by turning the machine off.

 

The logic board in this machine was very recently recapped. In fact, I just received the freshly-recapped board and installed it last Friday (May 29.) What's odd is that between May 29 and June 4, this machine worked flawlessly except the delay and pattern, which I and the member who recapped the board think is related to the ROM. (He tested it in another machine with a separate analog board and got the same issue... both before and after the recap. He said reseating the ROM helped the problem, but it persists. I'm thinking perhaps the ROM socket needs some DeoxIT?)

 

I guess the "computer Grim Reaper" visited overnight because this machine was literally working perfectly fine one day, the next day it was acting up, and now it's unusable. :cry:>:( And, of course, it all had to happen just as I was beginning to have fun with the machine.

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I agree low voltages. 

As you are able to boot from time to time, probably only capacitors for now. 

 

For troubleshooting purposes, I use a small psu for the hard drive only, and remove the floppy, that way the load on the analog board is limited to the Logic board. 

Edited by bibilit

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Should simply having the analog board bring the machine back from the dead? When I got the LB recapped, I was considering also having the AB recapped. But I decided against it because it wasn't showing any signs of failure, and I wanted to avoid/put off having to mess with the AB because of the risks of removing the neck board. (Am I being too anxious over the neck board?)

 

On a silver lining, recapping the AB would mean that this machine is 100% recapped... nothing to worry about. While I don't believe it is an issue on these "newer" compact Mac models, no more paper/RIFA/filter caps to worry about possibly going bang.

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Really, the neck board is no issue. As others have stated, removal and insertion, as long as done with some care, is not an issue at all. It is made to go on and off. As far as the analog board, first, it probably is a voltage issue/digital components not getting "clean" power/correct voltage for moving ones. Second, you cannot properly diagnose it without the analog board recap and ruling out the caps as the cause. Unlike the surface mount electrolytics on the logic board, unless the large ones on the analog board are really bad, they tend to not show any leakage, and not even bulge even though bad.

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In the photos I took of the machine before reassembling it last Friday, none of the electrolytic capacitors appear to be domed or leaking. Obviously, that doesn't mean anything.

 

If the caps are not causing the issue, what else could be causing the issue? My electronics troubleshooting skills is near zero...

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