Mac SE Fan Replacement

[rjkucia]

I just got a Mac SE which works perfectly!... Which means it's now time to mess with it

The built-in fan is loud (as is typical) and it seems easy enough to replace. My understanding is that a standard 12V 60mm fan like the Noctua NF-A6x25 FLX is a good replacement. I opened my SE up and examined the situation, and it looks like I should just be able to unscrew the existing one and the new one should fit right in. The only hard part would be cutting & soldering the wires, since it looks like the fan is soldered directly to the board (I didn't look too closely at that though).

Are my impressions correct? Are there any other considerations I should have in mind? Also, more of a general SE question, but what's the consensus on best practices for CRT/high voltage in there? I've seen a mix of opinions from "never open up a CRT or you will die immediately" to "it's fine don't worry about it". Since the fan is right next to the tube I just wanted to check on that to make sure I don't get fried! Thanks in advance.

 

[caver01]

Safety concerns are real, but you can also navigate inside a compact mac safely if you follow some basic steps. ALWAYS UNPLUG, and take the extra step of discharging the CRT anode before you start reaching inside. Whether you subscribe to the idea that the high voltage areas are well-insulated, there is never harm in taking extra caution. Also, if you power up again to test, UNPLUG again, and discharge again. Once you get into the habit, it is not a big deal doing this every time. UNPLUG. DISCHARGE.

As for the fan replacement, it is straightforward work covered by @JDW on youtube. I replaced my SE/30 fan. with a Noctua with success. This is certainly easier by taking the analog board out so you can lay it down on your workbench, but yes, the work basically amounts to de-soldering the old wires and removing the old fan and resoldering the new one. This is the cleanest method, but you can also splice to the existing wires if you want to avoid soldering on the board.

 

[rjkucia]

Thanks! That video answered a lot of my questions.

ALWAYS UNPLUG

lol, I got that far already by myself

discharging the CRT anode

I had more questions about this but JDW's video actually shows it in the SE, which is great! My remaining questions here are more general:
-During this process, what are the "DO NOT TOUCH" sections of the CRT so that I can properly avoid them prior to discharging? Not that I plan to touch anything unnecessarily, just so I can mentally mark off what's unsafe while doing it.
-Discharging specifically, I just get a screwdriver, ground it, wiggle it under the cap, and take the cap off, is that all? I should I expect to hear/feel something to know that I've done it correctly?
-The video board looks like it's attached to what I understand to be the weakest part of the CRT. Should I be extra careful here? It looks like JDW just wiggles it off, so maybe I'm overly-concerned about that.

 

[JDW]

I don't wiggle off that small PCB (CRT Yoke Board) until after I have discharged the CRT. The reason is because you have high voltage passing through that little board during operation, so if your CRT isn't fully discharged when you remove it, you leave yourself open to a potential shock. Not a "definite" shock, mind you. Just a potential one. Most SE's and SE/30's have bleeder resistors that should discharge the CRT though some minutes after you switch off power. And although there is the standard disclaimer that says, "those resistors could go bad," I've not seen one to date which has. Basically, the only Macs I have which don't self-discharge are the earliest Mac 128K's which have a flyback that lacks the bleeder resistor. Even so, everyone typically discharges the CRT anyway (with power cable removed), so as to avoid any possibility for trouble.

I remember many years ago that Stanford University EE professor Thomas H. Lee, author of the Classic Mac Repair Notes, once suggested cranking up the display brightness to max while powered, then yank the power cord to do an effective discharge. As a fellow EE, I can see the logic behind that. Something to try if you are worried, yet lack the screwdriver and alligator clip wire to discharge the CRT the normal way.

As always, you work in this old Macs at your own risk. But whether it be via bleeder resistor, Tom Lee's trick, or the normal discharge method, you really do need to have a discharged CRT before working on the analog board -- even if only the fan.

 

[caver01]

I appreciate your perspective here, as I imagine all of us were in a very similar headspace the first time touching CRTs. I am more worried about my hand slipping and breaking the neck than anything.

SO, the BEST way, so I have read, to discharge is to connect an appropriate/correct (big) resistor to the probe you are using (screwdriver) to absorb the high voltage current. In lieu of that, I see most recommendations to take a long flat screwdriver, attach wire with alligator clips to the metal shaft, and the other end to the top-left CRT mounting bolt (from the back) which is also the one where that little video board is attached with a string cable. And here is a nice rule of thumb: Clip on the alligator to that bolt, place one hand in a pocket or behind your back, and use the other on the insulated handle of the screwdriver and slip it under the anode cap. Push it under and touch the metal clip in there. This is hard to see, but if you push to a stopping point under the cap, you are there. The one-handed technique ensures you don’t accidentally touch something, but also prevent a path from arm to arm (through your heart).

As you approach the clip under the cap you may hear a CLICK like a static discharge. Frankly, I have NEVER heard this at all. I DID hear it discharging a television CRT the same way recently however, and scary thought—I did it again a few minutes later and had more! I have also read that some CRTs are setup with safety components that help dissipate the charge automatically. But these components can fail, so we always go through the exercise.

Once discharged, you can touch stuff. I tend to stay away from the yoke coils and ring adjustments and the little square magnets. No need to mess with the geometry these control, and they are probably glued in place anyway. The board on the end of the neck can now be safely pulled straight back and set to the side. This exposes pins and the fragile end neck of the tube, but it is way safer from getting bumped than it is with that board hanging off, and gives more clearance to your arm to reach the analog board connectors. After a while, you get pretty good at reaching the logic board to unplug the power molex and SCSI, but I am always worried my hand will slip and knock the neck.

You can also pull off that anode cap if you are planning to pull the analog board. The clip is like a reverse alligator clip, or a wisdom tooth with hooks. Squeezing the cap, or pressing one side in a bit with the screwdriver will help you lever it out of the glass hole. I have taken mine off so many times that the wire inside the cap broke off and I had to re-solder the clip. That probably was a partial root cause of some video issues I was having!

I think you start getting the hang of it after a while, so the videos you watch were people seem very casual about it—that is just experience and routine. You tend to know what to expect for the amount of force things take for example, so you can seemingly move more quickly through the steps.

You may have also noticed the adjustments for the CRT via trim pots and the horizontal frequency inductor from the outside of the analog board. RESIST the temptation to make adjustments without the proper tools (non-conductive, plastic, wooden). Example: It can be tempting to use an allen key to screw/unscrew the ferrite core in the induction coil to adjust horizontal while viewing the screen. First of all, this is metal part on a running, high voltage device! Bad idea. Second, you are usually making an adjustment around the side without looking at what you are doing. You would be better to use a mirror to see the screen. Third, an induction coil will heat a metal allen key very quickly!

That is a lot of description for what will end up being a pretty simple process for you. You will do just fine!

Good luck!

 

[JDW]

You don’t need to add any resistor in series with your wire and Flathead screwdriver when you discharge.

The alligator clip on your wire definitely needs to connect to the ground lug/bolt in the upper left corner of the CRT when looking at the CRT from behind. Don’t connect your wire to the metal chassis or any other place.

Most of the time you won’t hear a crackle when you discharge because the bleeder resistor has already done the discharge.

If you don’t use a resistor, and again you don’t have to, and you do hear a crackle when you discharge, it means there was a charge in the CRT, but now it’s gone.

And that’s it.

Most of the time you won’t hear a crack or when you discharge because the bleeder resistor has already done the discharge.

 

[pfuentes69]

Regarding the fan, if you are in a budget (as I try to be), you could also check something like this: https://www.aliexpress.com/item/32702728947.html?spm=a2g0o.9042311.0.0.27424c4dmFMUYm

I got several of those and put on my Classics and in the SE/30 and it does the job pretty silently (it claims to be 22dBA... surely is something more, but good enough).

 

[JDW]

Regarding the fan, if you are in a budget (as I try to be), you could also check something like this: https://www.aliexpress.com/item/32702728947.html?spm=a2g0o.9042311.0.0.27424c4dmFMUYm

I got several of those and put on my Classics and in the SE/30 and it does the job pretty silently (it claims to be 22dBA... surely is something more, but good enough).

At the rated speed of 2500rpm, the datasheet of that SUNON fan says it has an airflow of 13.8 CFM. Noise is a very lo 13.8 dB(A) as a result, but whether the near silent operation is worth the low airflow will vary by use case.

 

[pfuentes69]

At the rated speed of 2500rpm, the datasheet of that SUNON fan says it has an airflow of 13.8 CFM. Noise is a very lo 13.8 dB(A) as a result, but whether the near silent operation is worth the low airflow will vary by use case.

I'm sure the Noctua will be better, but I checked with a noise meter App and the noise level next to the fan was maybe about 25 dBA (I don't remember well), but for me it was lower enough for not being annoying anymore. The air flow after replacement was apparently better than with the old fan, but I couldn't check this in a "scientific" way.

On these Macs I'm always replacing the HD for a BlueSCSI or similar device, so I think this should also mean that the cooling needs are reduced somehow. Maybe it would be nice if someone with the right tools and knowledge can check how the cooling needs are affected after removing the spinning drive.

 

[JDW]

I'm sure the Noctua will be better, but I checked with a noise meter App and the noise level next to the fan was maybe about 25 dBA (I don't remember well), but for me it was lower enough for not being annoying anymore. The air flow after replacement was apparently better than with the old fan, but I couldn't check this in a "scientific" way.

On these Macs I'm always replacing the HD for a BlueSCSI or similar device, so I think this should also mean that the cooling needs are reduced somehow. Maybe it would be nice if someone with the right tools and knowledge can check how the cooling needs are affected after removing the spinning drive.

HDD replacement with an SD card solution will reduce current consumption and heat. However, if you add upgrades when consume more power and therefore generate more heat, the reduced airflow may be a concern, especially in the summer, unless you are blasting the A/C.

 

[rjkucia]

Thank you all so much! I feel a lot more comfortable with what to do now. I'll just order some alligator clips with the fan.

I'm just going to go with the Noctua. I got the one that works on Molex so I don't have to solder anything.

 

[rjkucia]

Swapped the fan today, worked great! Special thanks again to @JDW's video - it definitely helped when I got stuck a couple times! Those things are weird to take apart, haha