Thread
Just purchased Mac 512k
Lumpy -- Congratulaions on your aquisition ! 8^ ]
Other than B & R that Scott mentions -- an excellent store, by the way -- here's another one > MacTreasures
Enjoy !
:b&w:
Other than B & R that Scott mentions -- an excellent store, by the way -- here's another one > MacTreasures
Enjoy !
:b&w:
All:
I received the 512K late yesterday. A few things:
1) It's had the Mac Plus Upgrade - 800K internal drive and 128K ROM
2) It starts but it quickly shuts down... as though there is a short in the electrical supply. I cracked her open and found that if I flex the analog board a little, she'll power back on and stay on. But I have to flex the board just right by putting pressure on the rear top of the boar - pushing it toward the CRT. With the right pressure on the analog board, she stays powered - if I let off the pressure, she shuts down.
Beyond replacing the analog board - any tips on how to get this one running?
I'm disappointed that it's not original, and knew I was rolling the dice - but am having fun with it non the less. The case is in excellent shape (Light beige - no yellowing) and the CRT/Display quality is sharp with no burn in. A good example worth getting up/running.
Thanks,
Lumpy
I received the 512K late yesterday. A few things:
1) It's had the Mac Plus Upgrade - 800K internal drive and 128K ROM
2) It starts but it quickly shuts down... as though there is a short in the electrical supply. I cracked her open and found that if I flex the analog board a little, she'll power back on and stay on. But I have to flex the board just right by putting pressure on the rear top of the boar - pushing it toward the CRT. With the right pressure on the analog board, she stays powered - if I let off the pressure, she shuts down.
Beyond replacing the analog board - any tips on how to get this one running?
I'm disappointed that it's not original, and knew I was rolling the dice - but am having fun with it non the less. The case is in excellent shape (Light beige - no yellowing) and the CRT/Display quality is sharp with no burn in. A good example worth getting up/running.
Thanks,
Lumpy
You could be but a single dry joint, or a few dry joints, away from joy as was zeppelin87. The FBT is a prime suspect in this case, but tomlee59's description of the path to the promised land in the same topic is worth your consideration. A quarter-century or thereabouts of resonance in a large and hot component on the power/sweep board is a fine target during the first roundup of usual suspects.
de
de
Equill:
Thank you.
I was thinking the same thing after reading that document.
When the unit is started cold, it starts right up. Once she warms up, an electrical buzz is heard, then she shuts down. Flexing the power/sweep board gets temporary power back and she turns on for the amount of time I can keep the board flexed exactly right.
I have a solder iron. I removed the power/sweep board last night to look more closely at her. What do I need to do to trouble shoot a dry joint or two? Do I attack it from the back of the board? Re-heat each solder point and let it cool - in the hope of sealing the joint? Any guidance is appreciated - I am not what I would call experienced with a soldering iron - more of a novice.
I have a (used) replacement board on the way that is known to be good but it was $$ and I can return it in 7 days if I can get this old girl solid.
Lumpy
P.S. I ordered Pina's Macintosh Repair & Upgrade Secrets a few weeks ago - still waiting for it to arrive.
Thank you.
I was thinking the same thing after reading that document.
When the unit is started cold, it starts right up. Once she warms up, an electrical buzz is heard, then she shuts down. Flexing the power/sweep board gets temporary power back and she turns on for the amount of time I can keep the board flexed exactly right.
I have a solder iron. I removed the power/sweep board last night to look more closely at her. What do I need to do to trouble shoot a dry joint or two? Do I attack it from the back of the board? Re-heat each solder point and let it cool - in the hope of sealing the joint? Any guidance is appreciated - I am not what I would call experienced with a soldering iron - more of a novice.
I have a (used) replacement board on the way that is known to be good but it was $$ and I can return it in 7 days if I can get this old girl solid.
Lumpy
P.S. I ordered Pina's Macintosh Repair & Upgrade Secrets a few weeks ago - still waiting for it to arrive.
Update:
Watched a quick youtube video (or two) on how to solder electronics boards. Got my solder out and practiced on an old motherboard that I had lying around - then went and hit the main components (culprits) on the power/sweep board. Used new solder at most joints - hit about 30-40 joints...
Set the board back in the mac - powered up.... ran for a few minutes as usual - then electrical buzz to power down. No luck there.
Lumpy
Watched a quick youtube video (or two) on how to solder electronics boards. Got my solder out and practiced on an old motherboard that I had lying around - then went and hit the main components (culprits) on the power/sweep board. Used new solder at most joints - hit about 30-40 joints...
Set the board back in the mac - powered up.... ran for a few minutes as usual - then electrical buzz to power down. No luck there.
Lumpy
In even the relatively-large masses of solder implicit in holding large (in mass or current-demand) components to a power/sweep board, the integrity of the board-to-trace or board-to-land adhesion can usually be assumed. Nonetheless, look askance at obvious messily-reworked joints, and especially if the expression "dog's-breakfast" comes readily to mind.
'Dry' joints are rather found between pigtails and pins and the solder, and/or the solder and the land or trace. The stabilizing effect of through-board holes can help, as can the use of hot-glue blobs post-soldering, to prevent movement of the solderees® during the all-important freezing of the solder after its application. Also critical to good joint formation is that the solder 'melt' should properly 'wet' and bridge the surfaces being attached. Fluxing and cleanliness (jointly, 'wettability') of surfaces, immobility of the joint, and rate of heat input and escape during freezing of the solder are important in assuring a good joint.
The frozen solder is a solid solution of malleable metals. Tension and cyclic stress can therefore, in time, affect a joint's adhesive qualities, even to the point of separation of the metals/metalloids from each other by 'crystallizing out' of the solution. Dull finish and granular appearance of a joint may be evident, but increased ohmic resistance to the point of open-circuit is the clincher.
The remedy? Remake the joints. This needs all the gear and attention of the original joint-making. It may need only a dab of fresh solder and flux, or it may need aspiration of the faulty solder and its total replacement. Adequate cleanliness, heat input/removal and stabilization of the parts is important. A resistance-check across remade joints will be useful, but the success of the complete operation may not be apparent before the job is completed and the board is back in service. None of the foregoing guarantees no shorting in an FBT, or that bung capacitors or barbecued resistors will have healed themselves. The components on power/sweep boards are big enough for physical inspection to suggest replacement, when that is needed, rather than resoldering, and rugged enough that no fear of damage from static (given normal and tasteful precautions) should be a consideration.
This peroration may take longer to read than it takes to resolder a joint, with practice. You can practise on something inconsequential, such as a current Acer PC, and be up and running in no time at all. Rots of ruck.
de
'Dry' joints are rather found between pigtails and pins and the solder, and/or the solder and the land or trace. The stabilizing effect of through-board holes can help, as can the use of hot-glue blobs post-soldering, to prevent movement of the solderees® during the all-important freezing of the solder after its application. Also critical to good joint formation is that the solder 'melt' should properly 'wet' and bridge the surfaces being attached. Fluxing and cleanliness (jointly, 'wettability') of surfaces, immobility of the joint, and rate of heat input and escape during freezing of the solder are important in assuring a good joint.
The frozen solder is a solid solution of malleable metals. Tension and cyclic stress can therefore, in time, affect a joint's adhesive qualities, even to the point of separation of the metals/metalloids from each other by 'crystallizing out' of the solution. Dull finish and granular appearance of a joint may be evident, but increased ohmic resistance to the point of open-circuit is the clincher.
The remedy? Remake the joints. This needs all the gear and attention of the original joint-making. It may need only a dab of fresh solder and flux, or it may need aspiration of the faulty solder and its total replacement. Adequate cleanliness, heat input/removal and stabilization of the parts is important. A resistance-check across remade joints will be useful, but the success of the complete operation may not be apparent before the job is completed and the board is back in service. None of the foregoing guarantees no shorting in an FBT, or that bung capacitors or barbecued resistors will have healed themselves. The components on power/sweep boards are big enough for physical inspection to suggest replacement, when that is needed, rather than resoldering, and rugged enough that no fear of damage from static (given normal and tasteful precautions) should be a consideration.
This peroration may take longer to read than it takes to resolder a joint, with practice. You can practise on something inconsequential, such as a current Acer PC, and be up and running in no time at all. Rots of ruck.
de
equill - thanks for the thorough explanation. I did go back and retouch the key solder points. Getting each point to flow and, where necessary, touching up with new solder. Probably not to the level of detail that you specify.
In any case, I believe I have localized the issue to the Flyback transformer. It is the culprit that buzzes noisily as the Mac powers down...
It looks like I'm out of bullets (unless the flyback wheel can be serviced by me). I have a replacement power/sweep board on the way.
Despite all of this, I'm enjoying getting this old dog back on its feet.
Lumpy
In any case, I believe I have localized the issue to the Flyback transformer. It is the culprit that buzzes noisily as the Mac powers down...
It looks like I'm out of bullets (unless the flyback wheel can be serviced by me). I have a replacement power/sweep board on the way.
Despite all of this, I'm enjoying getting this old dog back on its feet.
Lumpy
I have replaced flyback transformers. It is quite easy actually. The key is to get your hands on a replacement. It sounds like you were quite thorough in your soldering, however, if you did not re-work the flyback connections, you definitely should. Of course it may not be the flyback at all, but rather some vital component in line with the flyback that is failing once it heats up, especially now that you have verified most of the solder connections. Though the fact you can flex the board and restore power certainly indicates the primary culprit is a connection, vs. a defective part. I believe equill hints at using a desoldering pump or braid to completely clean off the old solder which may be incapable of re-adhering properly.
You will find Larry Pina's book quite helpful in diagnosing and repairing problems on the analogue board as Tom Lee's article.
As for restoring it, internal 400K drives are relatively easy to find on eBay. Also, you might consider getting an external 400K drive. You can always swap the internal for the external (though the 400K case bracket needs minor alteration to hold the 800K drive. The internal 800K drive bracket may also need to be modified to hold the 400K if that is even possible (I know the reverse is true as Pina's book outlines).
It doesn't sound like you really need the 64K ROMs based on how you have described using it. However, look for dead 128K/512K logicboards that turn up on eBay all the time for very little. As I said before, the ROMs are usually in perfectly fine condition and can be easily swapped out to restore your 512K to it's original condition. Did you indicate whether this was originally a 512K, or a 512Ke? The model number on the rear label will be M0001E or D or ED if the latter and W if the former. You can also verify by the serial number which will start with F6 followed by a number greater than 12 if it is a 512Ke. THe reason I think it may be a 512Ke is because the original owner told you there were not any upgrades. They would have known if it had had the 512Ke upgrade since it was by no means inexpensive and typically had to be performed by authorized Apple service personnel.
FYI, depending on the 800K drive installed, it may work natively with the 64K ROMs just like the Apple 3.5 External drive does, meaning you only have to swap the ROMs to play around with it. The 64K ROMs don't like to have external drives attached when one of them is an 800K for some reason (it makes a constant clicking noise).
Mac128 - if you know of a source of flybacks, point me there - I'll buy one just to see if I can revive the board. I did re-work the flyback connectors...
The trick of flexing the power/sweep board was very flakey - I'm not sure if there was another loose connection and it was a combo of problems.
I do not need the 64K ROMs - but I was looking for a stock example. I'm not a collector though - just looking to relive the time when I owned my original mac and also love messing with this stuff to see if I can get it to work.
It was an original 512K - ended in "W" not "E". The Mac came with all of the original software and manuals - including the "Plus Upgrade" manual. At the end of the day, I think the seller played dumb - "it started the last time I started it 10 years ago". She also told me she thought it was stock... and packed me the upgrade manual and receipt. Live and learn....
I'm still pretty happy with the unit. The case is very light beige and in excellent shape - a good example if I can get her running. It came with some good software and included a lot of vintage Mac books. I may chuck the MacEnhancer up on Ebay and see what it fetches. It came with 4 different sets of disks - they were updates... so thats how Microsoft kept up with new printers.
Regarding the 800K drive - I'm going to stick with it... I have the HD20, so at the end of the day, the 128K ROM and 800K drive are fine by me. I'll get to run OS 6 as well.
I'll be updating this thread until I get her running!
Lumpy
P.S. I got to feel the full effect of a CRT discharge today while removing the Anode Cap. After doing it successfully 3 times, I got whacked when I was pulling the power/sweep board to ready the unit for a replacement board. Let's just say I'll be buying the discharge tools tomorrow. Mother F'er that hurt.
The trick of flexing the power/sweep board was very flakey - I'm not sure if there was another loose connection and it was a combo of problems.
I do not need the 64K ROMs - but I was looking for a stock example. I'm not a collector though - just looking to relive the time when I owned my original mac and also love messing with this stuff to see if I can get it to work.
It was an original 512K - ended in "W" not "E". The Mac came with all of the original software and manuals - including the "Plus Upgrade" manual. At the end of the day, I think the seller played dumb - "it started the last time I started it 10 years ago". She also told me she thought it was stock... and packed me the upgrade manual and receipt. Live and learn....
I'm still pretty happy with the unit. The case is very light beige and in excellent shape - a good example if I can get her running. It came with some good software and included a lot of vintage Mac books. I may chuck the MacEnhancer up on Ebay and see what it fetches. It came with 4 different sets of disks - they were updates... so thats how Microsoft kept up with new printers.
Regarding the 800K drive - I'm going to stick with it... I have the HD20, so at the end of the day, the 128K ROM and 800K drive are fine by me. I'll get to run OS 6 as well.
I'll be updating this thread until I get her running!
Lumpy
P.S. I got to feel the full effect of a CRT discharge today while removing the Anode Cap. After doing it successfully 3 times, I got whacked when I was pulling the power/sweep board to ready the unit for a replacement board. Let's just say I'll be buying the discharge tools tomorrow. Mother F'er that hurt.
Code:
Not really. Usually off of a dead board. Let Tom Lee or others weigh in before you attribute the problem to the flyback though. Pina's book has part numbers for the flybacks if ti comes to that (I believe JDW's excellent spreadsheet may also have those part numbers as well as others you might be interested in), most of which you should still be able to find over the internet.
You're going to make Charlieman cry ...
No need to buy tools. All that's necessary is a screwdriver and an alligator clip. I've done it this way successfully every time I discharge one. FYI leaving it unplugged for a day will usually mitigate the strongest charge. However, if you are going to be working on it in this fashion, make sure you not only discharge the CRT, but avoid the high energy caps on the analogue board as well. Pina's book details the construction and FYI, you don't really need the resistor, at least I never have. As a precaution, I would always remove the logicboard before you discharge to avoid any ancillary damage.
What? And you're not dead? OMG!
Sorry, I'm not poking fun at lumpydog. I am just railing on those who contend the Anode Cap can be lethal. I suppose it can be if you nail yourself just right, with a higher than normal discharge, and if you perhaps have a weak heart. But again, I've never in my life heard of someone dying because of such accidents. But as lumpy said, it hurts when you do get smacked. I don't know how it directly compares, by I shorted 110VAC across my pinky finger once in a high school electronics class. Man! Got the blood flowing, let me tell you.
So did you use Tom Lee's discharge method? (Screen up to full brightness and then yank the AC power cord?)
Laughing my ass off. As you said - not lethal. I've been shocked MUCH worse believe me. My mistake was in grabbing the case to get leverage - put my thumb on the ground screw. Stupid does not even begin to describe... So got what I deserved. I knew I was taking a short cut - won't do it again.
The main reason you'll usually hear about the dangers of CRTs is lawyers. Not to mention that most of the time when people talk about CRTs, they're often talking about larger colour CRTs used today, which pack a more lethal punch than the little 9" mono units used in the compacts.
I've been shocked by 240VAC (Australian mains voltage) twice. Scary as all Hell, but if you're lucky, and in good shape, survivable.
I've been shocked by 240VAC (Australian mains voltage) twice. Scary as all Hell, but if you're lucky, and in good shape, survivable.
I was putting together a panel with a big power switch (ideal for Igor), which I had the wrong way round as I had to switch it up to turn it on, so I put my hand under the panel to turn the toggle switch round...... hello said 240V, 50hz, UK mains.
Don't worry Charlieman - if I do, I'll post all the disks where we can get to them.
Nice! Thanks for that tip - I happen to have those things available.
I'll hold off on the flyback replacement to see if others chime in on this...
Even more to the point, lumpydog, is JDW's almost throwaway reference to the technique of preference by all except masochists.
de
Tried it today along with Mac128's non-resistor discharge tool. I'm feeling pretty good about not getting whacked by high voltage anymore...
Question: I just purchased a new (grounded) solder tool and a desolder bulb/sucker thingy. I can't for the life of me desolder some joints - the solder won't melt. It seems like the resistor (who's joint I am soldering) is somehow causing the solder to drain and not heat. At the risk of asking a serious noob question, am I missing something obvious here?
Lumpy
P.S. Having a blast trying to get this Mac up and running and presentable. I used h202 and oxi today to take a very yellow mouse and make it look brand new - wow (6 hours in the solution set out in the sun). Going to de-yellow the keyboard tomorrow. Oddly, the Mac's case looks great. Still waiting for a replacement sweep/power board and still looking to resurrect the exiting one.
Before:
(internals removed, just prior to dunking)After:
(internals cleaned, lubricated and replaced)No joke - all I did after putting it in the solution was rinse it. I did zero scrubbing.
Rational enough, but perhaps not obvious. Whether a blob of solder melts under an iron is the net effect of the old calories-in/calories-out bit. If the soldered-in component has a large thermal mass and a wide thermal path in, retention of heat to melt the solder may be impaired if the iron cannot quickly enough replace the calories that 'leak' into the component from the joint.
This is at least part of the reason why irons exist in sizes (wattages, and bit dimensions) from micro to those suited for connecting roof-gutter sections. Wattage is a time-dependent quantity (as is amperage, on which it is based), so a higher-powered iron is able to deliver heat to a given joint faster. You still don't wish to destroy the board or component, so you need to be able to touch/melt/slurp in one action, and then rest/cool the work before continuing, if need be. Sometimes connection of a heatsink to the work ('downstream' from the pont of heat-application) may help to preserve the component.
Best of all, you are enjoying what you are doing. May you continue to do so.
de
Please post links to the exact substance and brand you used or PM them to me.
Here's another de-yellowing example that is just incredible. I wrote Peter Dreisiger twice asking for the exact substance he used, but he must have fallen off the face of the planet because he refuses to reply.
I can't wait to de-yellow my IIgs keyboard with whatever it is you gentlemen are using!
JDW:
Below is a pic of the exact items that I used - along with a link to the forum that discusses this approach.
Here is exactly what I did:
1) In a plastic tupperware - poured the 3% hydrogen peroxide solution up to a level that could fully submerge the mouse.
2) Added (more or less) one tablespoon of the powdered Oxi cleaner to the hydrogen peroxide and mixed - some powder did not dissolve - I left it in the bottom (and it eventually dissolved during the day).
3) Dropped in the (electronics removed) mouse and set it out in the sun in my driveway (it was only 38 degrees out - temp should not matter). A source of UV light is the 3rd ingredient. Without it - you get nothing.
4) Rotated the container 180 degrees after 3 hours
I left the mouse/solution out for just under 6 hours then rinsed the mouse off in fresh water.
The results were astounding. A mouse that looks brand new - nice gloss finish with no noticable degredation of the plastic.
My observations:
- The hydrogen peroxide percentage was only 3% (see picture) - if you read the thread below, some people are working with 30-40% hydrogen peroxide solutions. I think it's not necessary and is dangerous. I personally think these guys are nuking their plastics way more then they need to...
- I'm not sure I needed to rotate the container or not. The bottom of the mouse was never exposed to sun - yet it de-yellowed. I think the UV light is a catalyst for the solution and does not need to directly hit the yellowed surface - I could be wrong.
- The apple logo can be damaged by this process (as shown in one of the threads I read about this process) be sure to pop out the apple logo on any parts with the apple rainbow colored logo - there is a hole behind it that you can use to pop the logo out - it is held on with a double sided clear sticky pad - light/persistent pressure from behind will pry it lose. The paper label with serial number on my mouse was not effected. Here is a logo that was damaged during this process: http://farm4.static.flickr.com/3175/2976915302_c7147f084e.jpg?v=0
- Some other de-yellowing methods include making a paste so you do not have to find enough hydrogen peroxide to fully submerge these parts - the paste uses a third substance (corn starch, etc) mixed with the hydrogen peroxide and Oxi to hold the solution to the surface -rather than submerge it .
Today, if the sun comes out, I will try to de-yellow a badly yellowed HD20 case and my keyboard. I will post before/after pictures and any more observations.
Links:
Picture of the exact items I used (all purchased at Wallgreen's):
Thread on deyellowing: http://www.vintage-computer.com/vcforum/showthread.php?t=12566
Equill - thank for this explanation - I did figure out that holding the iron away to heat up and then going back in helped...
I wouldn't take it personally, it's only been 8 days. :beige:
From reading his post, I am not sure having the exact brand would be helpful to you in Japan, though Pacific rim products might be common. However, I think he is referring to a standard pre-mix hair salon peroxide coloring treatment, essentially the same formula described in the link he references. That link basically describes how to make a similar gel. I would suggest going to a hair salon supply store and asking for a generic peroxide gel, then compare a few for ingredients. Most likely they will all be the same. They are designed to remove color, as in "peroxide blonde". Test on a few sacrificial pieces of yellowed plastic. Another related link discusses the amount of peroxide in the container and it ranges from 8%-20%, the higher the content the faster the removal. This method may be easier to acquire than locating a similar concentration of H2O2.
BY THE WAY: THIS INFO REALLY NEEDS TO BE ADDED TO THE 68K WIKI so that it does not get lost in the mostly un-searched archives of this forum. :beige:
Here are more examples of de-yellowing that I've done per my prior post in this thread.
Today I put my HD20 case in the H202/Oxy solution and left it outside for 6 hours. Note that I actually used 1/2 water and 1/2 3% Hydrogen Peroxide solution. You can really cut the H202 and get good results.
Case before (you can see the footprint where the Mac used to sit on top):
Case in the solution (used clear plastic to allow max UV penetration):
Case outside in the sun (UV):
Case after:
This is not a bleaching process - it does not over-whiten. Really amazing results... Gets the plastic back to the original color.
I have my keyboard surround in the solution now - sitting in my basement with a UV bulb. Pics forthcoming. I will add them to this post.
Lumpy
Today I put my HD20 case in the H202/Oxy solution and left it outside for 6 hours. Note that I actually used 1/2 water and 1/2 3% Hydrogen Peroxide solution. You can really cut the H202 and get good results.
Case before (you can see the footprint where the Mac used to sit on top):
Case in the solution (used clear plastic to allow max UV penetration):
Case outside in the sun (UV):
Case after:
This is not a bleaching process - it does not over-whiten. Really amazing results... Gets the plastic back to the original color.
I have my keyboard surround in the solution now - sitting in my basement with a UV bulb. Pics forthcoming. I will add them to this post.
Lumpy
That is really just amazing as are some of the pics on those other sites.
I know it's not bleaching since the color is not overly-lightened and the discoloration is the result of a chemical process, not an added pigmentation one. However, just what is happening here to return these cases to their almost mint condition? Is it literally reversing the chemical process within the plastic that originally turned it yellow?
It is also interesting to note, the very UV light that caused the Macs to yellow in the first place, is being used to reverse the damages as well. I wonder how long it will take for the yellowing process to begin again, once exposed to UV sources? Has the chemical reversal process lowered the plastics resistance to future yellowing or enhanced it? I guess only time will tell. Wonder if it would be worth spraying a transparent UV coating over the case and what that would do to the texture.
Without my wishing to rain on anyone's parade, let me refer back to an earlier discussion in these forums, and the posts that in turn hang off that discussion. We already have the makings of a good Read Me First for case-yellowing.
It is in the nature of ABS plastic to age chemically and irreversibly, not least for the same reasons that inspired the invention and use of plastics: they are cheap, nasty and easily-formed into shapes. True it is that a strong oxidizer may remove an infinitesimally-thin, strongly-coloured degradation product, as well as oxidizable dirt, from a Mac case. However, because the purely chemical discolouration of a case is oxidative in nature (there is far more free oxygen in air than there is reductive gas), use of an oxidant is not going to reverse it. ABS already contains reducing agents to prevent rapid yellowing, which will delay further yellowing as each new surface is exposed by abrasion, solution, crumbling or powdering. However, when the reductant has been oxidized, as is its purpose, the plastic has no further defence, and all that is possible is to begin the process again.
It should also be understood that hydrogen peroxide is perfectly capable of breakdown in the absence of UV radiation. Indeed, since UV light is one of the causes of case-yellowing, isn't it at least slightly perverse to try to accelerate the production of nascent O to remove yellowing with the same agent that has already been responsible for the yellowing? Hydrogen peroxide breakdown occurs readily enough on the surface irregularities of any but a microscopically smooth surface, let alone the textured surface of a Mac case. The only potentially beneficial effect of direct sunlight is to raise the reaction temperature of the process.
It is not sheer defeatism that causes many Mac owners to clean their Mac cases well, and then accept their colours as Nature will make them. There are quite a few counter-arguments to fretting unduly about case-yellowing.
de
It is in the nature of ABS plastic to age chemically and irreversibly, not least for the same reasons that inspired the invention and use of plastics: they are cheap, nasty and easily-formed into shapes. True it is that a strong oxidizer may remove an infinitesimally-thin, strongly-coloured degradation product, as well as oxidizable dirt, from a Mac case. However, because the purely chemical discolouration of a case is oxidative in nature (there is far more free oxygen in air than there is reductive gas), use of an oxidant is not going to reverse it. ABS already contains reducing agents to prevent rapid yellowing, which will delay further yellowing as each new surface is exposed by abrasion, solution, crumbling or powdering. However, when the reductant has been oxidized, as is its purpose, the plastic has no further defence, and all that is possible is to begin the process again.
It should also be understood that hydrogen peroxide is perfectly capable of breakdown in the absence of UV radiation. Indeed, since UV light is one of the causes of case-yellowing, isn't it at least slightly perverse to try to accelerate the production of nascent O to remove yellowing with the same agent that has already been responsible for the yellowing? Hydrogen peroxide breakdown occurs readily enough on the surface irregularities of any but a microscopically smooth surface, let alone the textured surface of a Mac case. The only potentially beneficial effect of direct sunlight is to raise the reaction temperature of the process.
It is not sheer defeatism that causes many Mac owners to clean their Mac cases well, and then accept their colours as Nature will make them. There are quite a few counter-arguments to fretting unduly about case-yellowing.
de
But even without the "defense" one could argue that since the plastics are restored to what looks like "new" condition again, and in light of the fact it may take at least a year in direct sun for the plastics to yellow so badly again, it would seem to me to still be worthwhile to do this. For even if one could show me that the plastics would yellow again, and even at TWICE the rate of new plastic yellowing, I could still content that the plastics would look like new for me for several years at least if I keep the machine out of direct UV light most of the time.
Also, in the Vintage Computing thread that Lumpy linked to, it says that at least one person did the same tests in a dark room (i.e., without UV light) and found that the case was not de-yellowed after soaking for several hours. The same alchemist then claimed that he did the same test in UV light and it produced the results we see in Lumpy's photos. But then again, those same alchemists also claim that you need 20% or higher concentrations of H202 to perform the task well, and Lumpy's 1.5% H202 mixture appears to prove that wrong. Which makes me wonder how important H202 is at all if a mere 1.5% works!
Yes. Something else, the "Oxy" compound contains sodium percarbonate, which when mixed with water releases H2O2 and sodium carbonate, the latter used to HELP dyes bond with fibers, not extract. It is some great irony that all that is employed here is mostly H202 and water, with the mixture's PH elevated by the sodium carbonate. UV, which normally is the enemy, is then used to activate the process.
And just for the record, here's the original published research into case yellowing:
http://www.vintagecomputing.com/index.php/archives/189
And according to this Vintage Macs post, "Bromine molecules" are the root cause of the yellowing, which the H202 is supposed to "neutralize."
Of course, complete immersion of an entire classic Mac case is not practical for many of us, so a gel version of Lumpy's mix would seem to be in order; which, from what I have read, is simply a matter of adding some corn starch.
Of course, complete immersion of an entire classic Mac case is not practical for many of us, so a gel version of Lumpy's mix would seem to be in order; which, from what I have read, is simply a matter of adding some corn starch.
The latter author's claimed experience might have been easier to believe if he had not miscalled acrylonitrile-butadiene-styrene copolymer (ABS) 'acetal-butadiene-styrene'. There is a significant difference. Implicating bromine (the next-heavier halogen above chlorine) may or may not be accurate chemically, depending on the proportion of flame-retardant in the plastic mix, but the similarity of bromine (an oxidizer) to chlorine (an oxidizer) surely has implications for trying to clean or 'undiscolour' oxidized and yellowed ABS with chlorine-based bleaches? The unanswerable point remains: by the time that yellowing shows, the incorporated antioxidants in the yellowed plastic have already been exhausted. There is no way of 'retrofitting' more antioxidant into the solid plastic. The available options are to:
1) clean off the surface yellowing (by whatever means and however much); then
2) coat the ABS plastic with UV-opaque clear finish, and to keep the cases away from heat and further UV-irradiation, or
3) live with the yellowing as it reappears.
Mac owners must follow their own courses. Both of the above courses are defensible, given that the treatment is revealed to a buyer along with a Mac's electrical and software specification.
de
1) clean off the surface yellowing (by whatever means and however much); then
2) coat the ABS plastic with UV-opaque clear finish, and to keep the cases away from heat and further UV-irradiation, or
3) live with the yellowing as it reappears.
Mac owners must follow their own courses. Both of the above courses are defensible, given that the treatment is revealed to a buyer along with a Mac's electrical and software specification.
de
I've been so impressed by the non-damaging cleaning effect of this process that I am going to do my Mac 512K's case as well - it is slightly darker on the left side - something that is now noticable as it sits on top of the very nice/clean beige HD20.
I have a large clear tub - I'm going to try it next weekend. I will be seriously cutting the peroxide percentage to get enough liquid to fill the tub. We'll see how it goes (how low can you go!?)
One other observation - I left my keyboard case in the solution last night. I had been putting these items outdoors to get UV light. It was late, so I put the keyboard in my basement under a UV bulb..... and shut off the lights (and the UV bulb) on my way out of the basement - duh. I forgot that the master light switch cuts all ceiling lights/outlets in my basement. Despite the fact that the keyboard was in the solution - with the absence of UV light, it stayed the same. The yellowing did not budge or fade. So - on the way to work this morning I left it in my driveway - should be clean by the time I get home.