Just purchased Mac 512k

[Mac128]

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.

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.

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.

You're going to make Charlieman cry ...

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.

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.

 

[JDW]

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.

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?)

 

[lumpydog]

What? And you're not dead? OMG!

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.

 

[LCGuy]

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.

 

[porter]

I've been shocked by 240VAC

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.

 

[lumpydog]

You're going to make Charlieman cry ...

Don't worry Charlieman - if I do, I'll post all the disks where we can get to them.

No need to buy tools. All that's necessary is a screwdriver and an alligator clip.

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...

 

[equill]

Even more to the point, lumpydog, is JDW's almost throwaway reference to the technique of preference by all except masochists.

So did you use Tom Lee's discharge method? (Screen up to full brightness and then yank the AC power cord?)

de

 

[lumpydog]

Even more to the point, lumpydog, is JDW's almost throwaway reference to the technique of preference by all except masochists.

So did you use Tom Lee's discharge method? (Screen up to full brightness and then yank the AC power cord?)

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.

 

[equill]

... 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? ...

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

 

[JDW]

I used h202 and oxi... all I did after putting it in the solution was rinse it. I did zero scrubbing.

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!

 

[lumpydog]

Please post links to the exact substance and brand you used or PM them to me.

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

 

[lumpydog]

Equill - thank for this explanation - I did figure out that holding the iron away to heat up and then going back in helped...

 

[Mac128]

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 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:

 

[lumpydog]

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

 

[Mac128]

Here are more examples of de-yellowing that I've done per my prior post in this thread.

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.

 

[equill]

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

 

[JDW]

...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.

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!

 

[Mac128]

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

 

[JDW]

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.

 

[equill]

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