Recapping the 128K, 512K & Plus Motherboard & Keyboard

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JDW
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Recapping the 128K, 512K & Plus Motherboard & Keyboard

Think the Macintosh 128K, 512K & Plus motherboards don't need a recap? Time to Think Different. It's been 35+ years since the debut of the 128K & 512K, folks. Fluid-filled capacitors don't have eternal life. Properly chosen solid Tantalum, on the other hand, will last the life of the board. My video below shows recapping of the keyboard too.

PLEASE watch the video below on YouTube so you can expand the text description under the video, as it contains Mouser Carts and important info, especially for you Mac Plus owners.

https://youtu.be/vz2NGF5Vuao

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I found the concept good, but...

I found the concept good, but the execution of it somewhat painful.  I don't think it's practical to desolder all those caps using solder wik.

But if you must, then I suppose that's an alternative to using a solder-sucker or professional solder extraction device.  Though I must applaud your efforts!  The video was well done BTW.  The replacement capacitor choice was very good as well.

Next time, after you remove the solder on the bottom of the board and straighten out the belt lead(s), simply heat up the joint and gently pull the capacitor straight out, 1 side at a time.  That way, you're not using solder-wik on both sides of the board.

From there, you can use the solder-wik to clean the via.

Thanks for sharing your experience in re-cap'ing a motherboard.

 

 

JDW
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Thank you for watching part

Thank you for watching part of my video, but your comment seems to show that you did not watch it all.  I demonstrated the difficulty of using not only a wick to desolder the stock axial capacitors on that multi-layered motherboard, but I also showed that a desoldering pump and a professional desoldering station really don't work well either.  That is why for the 3rd and final axial capacitor on that board, I showed the faster, easier and more bullet-proof way whereby you merely clip off the old capacitor at the body, then solder the new axial replacement capacitor onto the existing legs.  

Due to the board being multi-layer, the inner layers of copper act like a heatsink, making the traditional method of desoldering quite troublesome indeed.  Some people have reported success using a hot air station, but the average person doesn't have access to that or the desire to purchase one.  Since my videos are for the average vintage Macintosh owner, the technique shown for the 3rd and final cap is what I suggest, as I mention in the video, since you don't need to worry about desoldering anything, and the end result doesn't look bad either.

One will also note that I show capacitor replacement on the keyboard, which is an easy job because there is only copper on the bottom.  It's a completely different situation than the multi-layer motherboard.  Therefore, on the keyboard, one can easily use a desoldering wick to competely remove the stock capacitor and then solder in the replacement.

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I did watch the entire video, though my comment

I did watch the entire video, though my comment concentrated on the solder wik more than the 2 other extractors you used.  I did in fact watch the entire video.

I'm familiar with the solder pump you used, and those are only as good as the tip on them.  The large extractor you used -I've never had experience with one of those so I cannot comment.  I use a Pace unit but those are not for most home projects like this unless you do it as a profession.

But next time, try this: (I do this on the road when I'm truly depsperate and  have nothing but a soldering iron and an ink pen)

Desolder the bottom of the leg (bottom of the board) to the point where you can bend the lead straight up.  Do this for both legs of the capacitor.

Then put fresh solder on the leg, and while the solder is molten, the capacitor should lift out of the hole easily using the capacitor itself as the object you gently pull up with.  It's a two-hand operation but it should come out easily. -much more so than trying to grab it with needle-nozed pliers, which as you note cool the joint.

Do the same for the other capacitor leg as well.  Then to clean the holes, heat the solder pad up again and  take a straw and blow through the hole while the solder is molten.  No solder wick needed!  You can do this much faster and with more assurance that the hole (or via) isn't damaged.  I'd love to show a video on it but I think you can imagine the process pretty easily.

Try it.  You might consider this next time you replace a motherboard capacitor.  Tell 'em MacNoyd sent ya!  ;-)

 

JDW
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Please accept my humble and

Please accept my humble and sincere thanks for your not only having watched the entire video, but for also making time to offer me your very kind and detailed advice.

I would love to see a video from you on this subject though.  Specifically, a video on the video motherboard and caps I dealt with.  I've been soldering for 33 years, using a variety of tools and techniques.  The axial capacitors on this particular board are especially difficult due to the sheer amount of copper connected to them on the hidden inner layers.  I worked on the second Axial capacitor for well over an hour before I could get the legs removed and holes cleaned out enough to fit the legs of the replacement. I of course, did not put all that footage in my video.  I actually tried blowing using my L-size rubber rocket blaster (not shown in my video), but that only served to harder the molten solder.

After having desoldered many components on many boards, I would say that 128k/512k board ranks among the hardest to desolder when it comes to thru-hole axial capacitors.  As such, having a video from you on that very board showing your techniques and showing how long it takes you from start to finish would be an excellent educational tool.  Conceiving of how a thing is done is all good and well, but it's no substitute for actually seeing it!

Lastly, I still feel that my advice to "the average person" in the video is sound.  Most people have zero soldering experience.  For them, trying to advise the required techniques to fully desolder the capacitors on the 128/512 board is at a higher risk of their damaged the board; specifically, adjacent traces.  I then becomes a repair job for them.  That is why I gave the closing conclusion that clipping off the old cap and using the remaining legs is a sound choice.  Due to it being a multilayered board, with legs so hard to remove anyway, you won't accidentally soldered the existing legs when you solder a replacement cap onto them.  And the end result doesn't look that bad either (not that you will be mounting the board on a wall and staring at it perpetually post recap anyway).

Again, thank you for your advice.  I look forward to your video! :-) 

 

 

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Oh my, a recap of a 128/512?

Oh my, a recap of a 128/512? Seems extraneous, especially w/o a rework station that has a desoldering iron as a component...

Best wishes!

 

Be very careful as breaking a via is a death knell. 

JDW
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As mentioned in my video,

As mentioned in my video, there are the naysayers who feel a recap of the 128K/512K/Plus motherboards are not necessary.  These folks base such thinking mostly on hearsay.  Meaning, they don't hear about problems pertaining to the capacitors on a 512K motherboard versus an SE/30 motherboard, and because of that alone they feel only SE/30's or Mac Classics need to have their logic boards recapped but not the 128K~Plus.  The reason that is flawed thinking is because no fluid-filled electrolytic capacitor has eternal life.  It doesn't matter if the capacitor is radial (legs coming out the bottom) or axial (legs exiting the sides).  If it's fluid-filled, at some point, it will need replacement.  The Axials potential can last longer, as I mention in my video, because gravity pulls the fluid down to the lower half of the body, where there are no exit holes, versus a Radial cap where gravity can pull the fluid out the leg holes.  But that doesn't mean Axial capacitors last forever.  And even if one argues that the capacitor was not used in a hot environment, such as the capacitor in the 128K keyboard, the fact remains that time and degrades the electrolyte.  Entropy is real.

The purpose of recapping relates to the purpose of the capacitor itself.  Capacitors are used in timing circuits, filters and to prevent voltage dips.  When a capacitor ages, it slowly becomes more like a resistor than a capacitor.  If the capacitance becomes much lower (lower than the typical 20% tolerance it originally had), timers start outputting pulses that are out of spec, filters shift and cut the wrong frequencies, and voltage dips the impact the entire circuit.  Recapping eliminates those problems by restoring the capacitors to the original or better condition.  In the case of my video recap, an all Tantalum recap not only provides lower ESR but also a stable ESR across the full operating temperature range.  Electrolytic capacitors have dramatically increased ESR at very low temperatures, whereas Tantalum is unaffected.

There is much, much more than can be said on this subject, but suffice it to say the 128K & 512K motherboards are now more than 36 years old.  Even if there is no sign of leakage, capacitors have degraded through the years that warrant a recap.  As shown in my video, desoldering the entire stock capacitor may seem to be most aesthetically pleasing but in fact it can be difficult or even impossible for some people who lack the right tools or experience.  The good news is that anyone can do this job, as I demonstrate with the 3rd and final axial capacitor on the 512K motherboard, merely by clipping off the old capacitor body and soldering the new capacitor onto the old legs.  The heat dissipation of the multi-layered board ensure the stock legs will not move around when heat is applied to them for several seconds to solder on the new capacitor. 

All recapping is troublesome to do but most of the time it is worth doing, especially on a machine more than 36 years old.

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