Just purchased Mac 512k

According to the BOMARC and Apple SE/30 schematics I have, ... C16 is a chip capacitor which, unlike the big tanks on the top side of the board, don't tend to fail over time.

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Uh, JDW, this is a 512K. C16 connects to a whole different place on the 512K and looks like it is a tiny polystyrene dielectric cap. The 512K uses no SMD chips of any kind.

Unfortunately, as you point out, Pina is rather mute on logicboard parts. I really don't have a clue either. Perhaps Tom Lee would weigh in, if he's following. Otherwise try a PM to him.

My C16 is on the opposite side of the board from the reset switch...

I'm not good at identifying these small parts. My ohm meter was able to get a reading from all identical diode/resistors (not sure which this is)- as long as the posative and negative test pins (from the multimeter) were on the correct ends.

The diode/resistor in qustion is clear/glass-like with a peach or orange band at the ends. There are a lot of identical looking diodes/resistors that I can get readings from.

JDW - I'm not sure C16 is the same on my board as the part you are describing on the SE30...

Lumpy

Edit: Mac128 and I posted at the same time...

Just looked at my C16 under a magnifying glass. It has definite markings on it. It appears glass with gold tips and a flat strip of metal bridging the connectors.

z50V

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Mac128 - that's it.

Any multimeter reading using an ohm meter? Positive/red further away from RTC... I get nothing - resistance, continuity....

Here is a picture of the part (JDW's picture off of Flickr) - I circled it in Red: http://www.flickr.com/photos/33624199@N08/3277349640/sizes/o/

Mine is damaged and illegible. I'm new to this, but think I've found the culprit.

Thanks

P.S. Your quote - is that what your reading off of the part throught the magnifying glass?

Ok, ok... That's what I get for posting at mid-night!

With respect to the Mac 512k logic board...

1) According to the hi-rez photo of my board (which I cannot post on Flickr because I haven't shelled out the cash for "Pro") shows C16 rated at 50v.

2) C16 is a Glass-Encapsulated Chip Capacitor, which of the same sort as I mentioned in my posting last night -- not prone to failure relative to electrolytics. You would need to test it out of circuit to know for sure though, and I wouldn't advise that unless you really know what you're doing because you could destroy it in the process.

3) According to my Mac 512k schematic, C16 is marked as "0.1" (the same as C15), and connects to an op amp on the board (which in turn connects to a transistor pair, which ultimately leads to the Audio Jack). As I said last night, I am going to assume this "0.1" value translates into 0.1uF. Another thing that leads me to believe this is true is because on my schematic, C15 is clearly marked "0.1uF" because there is enough space to write "uF" but there is not enough space to write "uF" after the "0.1" of C16.

4) Yes, this schematic I have is the "technical aid only" marked version, created by Apple engineers for "easy readability on one page" versus the original multipage schematic. But I still believe it to be accurate. (I can't remember if it was Guy Kawaski or Daniel Kottke who requested this from Apple engineers, because the original multi-page schematics were too troublesome to read at a glance.)

3) According to my Mac 512k schematic, C16 is marked as "0.1" (the same as C15), and connects to an op amp on the board (which in turn connects to a transistor pair, which ultimately leads to the Audio Jack).

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The schematic I have been working with is this one, showing pin 8 of the RTC going to the battery. On my 512K logic board, there is a trace going directly from the RTC-side connectoion to pin 8 of the RTC chip, which can be clearly seen on your flickr photo. So I'm not sure I agree that it goes to the Audio jack.

And yes, lumpydog, the markings are on the capacitor itself as seen through the magnifying glass. However, in sampling several boards, I discovered depending on how the cap was mounted, the marking could be on the bottom.

Mac128, look at section 3-D of the Digibarn 512k schematic you link to. You can see the word "AUDIO" just above J1 (the audio jack). Follow the lines from J1 down and to the left, through the transistors and op-amps. You can then see C15 just above C16. It is this C15 and C16 that I refer to in my post above.

Mac128, look at section 3-D of the Digibarn 512k schematic you link to. You can see the word "AUDIO" just above J1 (the audio jack). Follow the lines from J1 down and to the left, through the transistors and op-amps. You can then see C15 just above C16. It is this C15 and C16 that I refer to in my post above.

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Ah. Again, the only problem I have with that is I cannot trace back to C16 on the actual board. I'll post a traced route on one of the unfinished logicboard photos when I can. But C16 appears to be equivalent to C21 on the Digibarn schem, i.e. a trace directly from pin 8 (battery) of the RTC to a 1mF C16 which is terminates into a ground. The DB schem. shows C21, which literally appears to attach to nothing on the actual board. Is it possible that the actual production board differed from this schematic?

UPDATE: I think my supposition is quite likely. The schematic seems to refer to this board which DigiBarn indicates is the final board ("200 BUILD"). The board I was going to use to back-trace is noted as the FINAL board. NOTE: C16 is NOT in the same place on the 200-BUILD board, or the "Final" board as on the actual production boards. ALSO NOTE: the 200-BUILD part number is 820-0068-00, the "Final" board is 820-0086-B and the actual production board is 820-0086-C. Amazing. It's definitely worth taking a look at the schematics and updating them against the actual production board which seems to have a major re-working of the B&C/1&2 sections. This had the effect of changing the component numbering across the board.

I back traced what is indicated as C15 on the Final board (C21 on the 200-BUILD) and C16 on the production board. Even this is a significant difference as the Final and 200-Build boards definitely traces back from CLK pin 8, directly to the battery pin 11, respectively. This seems to indicate this area was constantly changing between this schem. draft and the production build. So the lesson here is don't rely exclusively on schematics. Are there indeed ANY schematics available for the final rev. B board (or even photos of unpopulated boards to compare revisions)?

I believe this has come up before, but since both the rev. B & C boards are © 1983, it is unlikely the rev. B board made it into any production models. It is worth mentioning that a final rev. was made to the board, though the board itself was not modified. A resistor network was attached to the VIA chip (the chip responsible for interacting with the RTC) and C30, which Larry Pina describes on page 179 & 183. Evidently it was added to the later boards to prevent a tendency for the Mac to "lock up". Without testing the absence of this resistor may or may not affect the RTC settings.

Yes, the white silkscreening of all three boards you mention are different. My Flickr photo shows the 820-0086-C board which differs from the "Final" board shown on Digibarn.

Therefore, the 512k schematic on Digibarn (from Dan Kottke) is a general reference only document that we should not rely on to help us debug production "C" boards. For reliable work on these production boards, we need a BOMARC schematic (which are reverse engineered based on actual boards).

For reliable work on these production boards, we need a BOMARC schematic (which are reverse engineered based on actual boards).

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Do you only have the SE/30 schematics?

Too bad this one is not more legible.

Correct. The only BOMARC schematics I have are of the SE/30. But I also have Apple schematics of the SE/30. I've compared them in many places, and they appear to be the same (which is reassuring). BOMARC does a great job.

Man. Your link to those Beck-Tech schematics have me drooling now. Anyone know someone who used to work there who could provide us readable copies?

Beck-Tech sold the schematics so there should be a few copies around.

Beck-Tech sold the schematics so there should be a few copies around.

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You have to wonder how accurate they are and why Apple would allow them to be sold contemporarily with their technology.

lumpydog, my apologies for hijacking your thread, but at least we know that C16 may be suspect and should be easy enough to replace, before you go looking for an RTC replacement. If not that, then I think you have to really start suspecting that clock.

Having said that, this seems as appropriate a venue as any to post this. I found this ebay auction for a 820-0086-F logicboard. The seller confirms the part number, though he has not confirmed the picture or whether it has 128K or 512K RAM installed. BOMARC likewise shows a 128K/512K 820-0086-C/F board, but does not show a 820-0141-A hybrid board, which is the only 512K variant I have seen.

So what is going on here? Is the "F" variant actually the original part number for the hybrid "Fat" Mac board? If so, why change the part number? Was the hybrid board further redesigned? Or did Apple decide the redesign was more significant than to be labeled a mere revision of the original? The only other reference I find to the "F" board is this website which also shows the same picture of a hybrid board as the eBay seller does. Not enough to ensure both are not using the wrong picture, but seems unlikely.

Mac 128 - this thread has covered so many different things, I don't think it could be hijacked...

Update on my Mac 512K: Still no luck with the clock. I did de/resolder the RTC chip. No luck. I purchased a 512Ke on eBay (arrived Friday) and swapped logic boards. Clock worked. So it confirms it's something on the logic board. I'm still focusing on C16 as it looks damaged.

JDW - I did de-yellow my Mac 512K AND 512Ke cases in the solution this weekend. This time, the mix was 1/3 Hydrogen Peroxide - the rest was water (and Oxi powder). Used a big plastic clear storage bin (I think my wife bought it at Target). Six hours in the sun. Results were the same as the other parts - incredible. The plastic model number sticker on the back - undamaged. The Apple Logos and Labels - undamaged (I did not remove them - watched closely). The serial number label - some water seepage/absorption around the edges but it dries out.

Another thing to mention - after the plastics come out of the solution and are dry, I've been using "Aerospace 303 Protectant" on them. The 303 Aerospace Protectant has a UV block.

I purchased a 512Ke on eBay (arrived Friday) and swapped logic boards. Clock worked. So it confirms it's something on the logic board. I'm still focusing on C16 as it looks damaged.

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Since we've determined the C16 directly interfaces with the power supply into the RTC it is definitely worth replacing if it looks suspect anyway. However, I don't think you can conclude it is not the RTC without actually swapping the known good RTC for the bad. Try the C16 first (perhaps borrow the one from the good board), then swap the RTC if that doesn't work.

The Apple Logos and Labels - undamaged (I did not remove them - watched closely).

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The 512K and HD20 had entirely different logos from the picture that showed the corrosion (and LC?). I wonder if the diamond-cut inlaid logo was stamped out of a steel alloy while the square 3-D logo was stamped out of something less reactive with the H202 like aluminum.

I've been using "Aerospace 303 Protectant" on them. The 303 Aerospace Protectant has a UV block.

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Interesting stuff. I can remember using something like it to clean my mom's patio furniture in Florida. It must leave some kind of film on the case in order to work, though I assume it is undetectable? As such, it would seem necessary to reapply to maintain effectiveness. This is a good solution since it should allow for repeated dunkings as the unit yellows from heat and chemical breakdown. Would be nice to leave it on display in a sunlit room without having to worry about the UV degradation which seems to be ironically both the Mac's main nemesis and savior.

Interesting stuff. I can remember using something like it to clean my mom's patio furniture in Florida. It must leave some kind of film on the case in order to work, though I assume it is undetectable? As such, it would seem necessary to reapply to maintain effectiveness. This is a good solution since it should allow for repeated dunkings as the unit yellows from heat and chemical breakdown. Would be nice to leave it on display in a sunlit room without having to worry about the UV degradation which seems to be ironically both the Mac's main nemesis and savior.

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The 303 Protectant is nice because it does not make the plastic look wet or feel slick like Armorall does. It gives the plastic a "new" look.... The UV block is a bonus. Not sure how long that lasts, but after the H202 dunk and the 303, the plastic looks brand new. I'm pretty pleased.

I'd love to see some crisp closeup shots of the BEFORE and AFTER 303 application (after the H202 dunking).

JDW:

I have a keyboard that I washed and have not yet treated with 303 - this weekend I will take some pictures of is (before/after 303 protectant) and some pics of my cleaned 512K and 512Ke.

Charlie

I appreciate those photos, Charlie. And I am very curious how the compact Mac cases will fair in light of the gray colored spray on the inside of the plastic case. Mac128 mentions that metal under the Apple logo could have resulted in the destruction of the colored paint on that same logo. Hence I wonder what will happen to that gray paint. Because doesn't that gray coating contain metal flakes in it?

JDW:

I'm not sure about the content of the gray paint used on the interior.... Mine looks fine after being dunked.

I promised some pictures - see: http://www.flickr.com/photos/33624199@N08/3301745527/ you can move through the series by clicking to the right (you know the drill with Flickr as I've seen pictures posted by you there).

The first series of pictures is of my 512Ke - which has been treated in the H2O2 solution and then wiped down with 303 Protectant.

The last six pictures show a keyboard after it had been washed in H202. The first three are before 303 had been applied - the last three are after. It's hard to tell the difference up close - but the protectant does make the plastic look slightly newer. More of a satin finish - but not wet (like Armorall) -and it does not feel slick or slippery/greasy.

Let me know if you have any more questions.

Oh - one other observation. I think the Compact Macs can get away with such a low percentage of Peroxide because the plastic is relatively soft/porous. I put the yellowed plastic from my MacEnhancer case in the solution - 3 days so far and it's only slightly changed.... Also - you will notice in the pictures that the spacebar on the keyboard of my 512Ke looks pretty good - that took 4 days out on the sun and 1/2 to 1/3 3% solution to get it looking that close to the other keys - it's a harder plastic...

I'm not sure about the content of the gray paint used on the interior.... Mine looks fine after being dunked.

the spacebar on the keyboard of my 512Ke looks pretty good - that took 4 days out on the sun and 1/2 to 1/3 3% solution to get it looking that close to the other keys - it's a harder plastic...

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The gray paint has a metallic content. The whole point of it is to prevent RF interference. Given that the RF shield is aluminum and the Apple III used a solid aluminum chassis, my guess is, it's an aluminum based paint. Aluminum is not particularly reactive with H202.

As for the spacebar ... that explains a lot, in particular why it tends to discolor and the other keys do not. Clearly supplied by a different manufacturer. Did you dunk all of the keys as well as the spacebar? If so, how long did they take by contrast?

The gray paint has a metallic content. The whole point of it is to prevent RF interference. Given that the RF shield is aluminum and the Apple III used a solid aluminum chassis, my guess is, it's an aluminum based paint. Aluminum is not particularly reactive with H202.
As for the spacebar ... that explains a lot, in particular why it tends to discolor and the other keys do not. Clearly supplied by a different manufacturer. Did you dunk all of the keys as well as the spacebar? If so, how long did they take by contrast?

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I did notice that any screws put unto the H202 solution suffered from minor corrosion (steel?) I think you may be right about aluminum. Also, I am using a much lesser percentage of peroxide - compared to the solution that ate the Apple logo in the earlier picture that I linked to.

I did not dunk any of the keyboard keys - with the exception of the spacebar, which was clearly yellowed in comparison to the rest.

Apple would have to be careful with any aluminum - based paint. If it came into contact with steel parts/screws - Galvanic corrosion.

Lumpy, so how many cups/tablespoonfuls of that OxiClean powder are you using versus the total volume of Water + H202 again? (For example, 1 cup Oxiclean to 1 gallon of H20 + 1 gallon of H202 @ 3% concentration -- 2 gallons total liquid, with 1.5% H202 concentration?)

It also seems that you are just leaving the plastic items in the solution, out in the sun, until your eyes see a physical change in the color of the plastics, correct? That explains why you removed some items after several hours in the sun, while others were not removed for 72 hours or so (which includes sunlight and darkness at night).

JDW:

The solution's percentages have been pretty approximate... but here is what I've used:

First time (Mouse): 100% Bottled Hydrogen Peroxide (3% concentration), 0% Water. For each gallon of this solution, a tablespoon of Oxi... maybe a little more

Second time (HD20 Case) (Needed more fluid to fully submerge larger plastics in larger tubs): 50% Bottled Hydrogen Peroxide (3% peroxide concentration), 50% Water. For each gallon of this solution, a tablespoon of Oxi...

Third time (Mac 512 Case) (Needed even more fluid to fully submerge larger plastics in larger tubs): 30% Bottled Hydrogen Peroxide (3% peroxide concentration), 70% Water. For each gallon of this solution, a tablespoon of Oxi...

Yes, I've been eyeballing it - I don't think there is a "too long" in the solution - the plastics don't get any lighter after a certain point, when the yellow is gone.

The diluted H202 seems to be just as effective as the undiluted. I've been cleaning out my local Wallgreen's supply of bottled H202. At less than $2 per bottle, I've purchased about 15 bottles to date. The recycling truck must think I'm nuts.

If you're concerned, try it on your mouse first - you wont need much solution or a big container... Use a clear plastic container to get max UV penetration.

I used the 303 Protectant, because I reasoned that it would protect the plastic and replenish it/keep it from drying out. The protectant improves the result.

I did notice that any screws put unto the H202 solution suffered from minor corrosion (steel?) I think you may be right about aluminum. Also, I am using a much lesser percentage of peroxide - compared to the solution that ate the Apple logo in the earlier picture that I linked to. ...

Apple would have to be careful with any aluminum - based paint. If it came into contact with steel parts/screws - Galvanic corrosion.

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The screws would most definitely be steel, cheapest of all the screws and no reason to use anything else. Actually you may be onto something re: the aluminum reacting with steel. The coating is judiciously applied and no metal parts come into contact with it at all. Of course they couldn't for electrical reasons. In fact, the only part that does come in contact with it is a specially designed aluminum strip mounted to the case that comes into contact with an aluminum patch on the analogue board left exposed through the vinyl. As Apple's tolerances were ridiculously tight, they later added a plastic liner that ran the length of the logicboard extending from the RF shield to prevent any contact by the chassis or logicboard caused by misalignment. I believe the steel chassis is further coated as well, though the sharp edges certainly defy any protective coating.

My yellow-capped 24oz tub of Oxi Clean "Versatile" arrived recently. While this product is clearly being used outside its intended purpose in restoring classic computing plastics to their original pristine color in combination with H202, I did find it interesting that the label recommends "warm to hot water" (apparently to dissove the OxiClean powder). And yet they recommend rinsing in cool water. Not sure why cold is required for the rinse. Here is the exact text off the label:

USAGE GUIDELINES1) Test in an inconspicuous are first. Rinse, then allow to dry. Always follow the manufacturer's instructions for water temperature and for cleaning garment or item. OxiClean works best in warm to hot water. Treat stains while fresh. Always rinse well with cool water. Do not place fabric that has not been thoroughly rinsed into dryer.

2) Do not use on wool, wool blends, silk, silk blends, leather or on fabrics labeled dry clean only. Not for use on jewelry, latex paints, woven baskets, unpainted wicker, jute, teak, or finished woods. Metals must not be soaked and must be rinsed immediately and thoroughly. Not for use on rust, dried paint, or bleach damage. Safe for septic tanks.

3) Keep container closed and dry between uses.

4) Some stains require repeated, longer or stronger treatments. Adding more OxiClean powder than recommended increases the risk of color loss. If washing in cold water, pre-dissolve OxiClean first in 16oz of warm to hot water. Add to cold water/wash.

WARNING

...AVOID PROLONGED CONTACT WITH SKIN...WEAR GLOVES WHEN MIXING OR USING SOLUTIONS. DO NOT STORE UNUSED SOLUTIONS FOR MORE THAN 6 HOURS, AS PRESSURE CAN BUILD UP AND RUPTURE THE CONTAINER AND CAUSE INJURY.

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I asked Lumpy about "tablespoonfuls" of this powder in a previous post, but the instructions talk about "scoops" with the included plastic scooper. Since the scooper holds more than a tablespoon, I assume you meant "1 scoop" instead of "1 tablespoon" correct? But even at 1 scoop per gallon, it is still less than the "SOAKING" and "HARD SURFACES" instructions recommend. Those instructions say 2-4 scoops per gallon of water.

JDW:

I was using the scoop to dispense the powder, but the amount I was using was roughly a tablespoon - albeit a heaping one. I didnt pay much attention to water temp - the Oxi dissolved pretty easily. You can see from my pictures that it was set outside in 30 degree temps.

In one batch I added too much Oxi and the surface got pretty foamy - not a big deal, but it did obscure some of the sunlight in the tank of water. My recommendation is to start with less - and strengthen if you're not seeing results. Otherwise, you're just wasting materials and subjecting the plastic to a stronger than necessary solution.

On the vintage-computer.com thread that I link to, I believe they mentioned that the solution stays useful for about 4 days...

In the 3-4 batches that I washed, I was not scientific in my measurements - all of the results were the same though. As I mentioned, start out with something small (your mouse) and see what you think. Harder plastics (keyboard keys) take longer and de-yellow more gradually. Softer plastics (most Apple case materials used in compact Macs) seem to de-yellow in diluted solutions in about 6 hours.

The screws would most definitely be steel, cheapest of all the screws and no reason to use anything else.

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For durability when inserted by machine tools and/or idiots, most computer screws are steel and have a bright plating which serves no engineering function. Case screws have coarse threads because their security is unimportant and the female thread may not be well formed. Some screws are japanned (ie given a gloss black coating) for aesthetic reasons, similar to plated screws. In the early days, Dell and other PC clone manufacturers used plain steel screws. PC motherboards are secured by brass mounts which use fine threads -- I don't understand the reason for this, unless it is just copying what IBM did donkey's years ago.

Actually you may be onto something re: the aluminum reacting with steel. The coating is judiciously applied and no metal parts come into contact with it at all. Of course they couldn't for electrical reasons.

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Inside a compact Mac, the RF paint is probably aluminium and carbon suspended in acrylic. The paint is too grey to be aluminium on its own.

I believe the steel chassis is further coated as well, though the sharp edges certainly defy any protective coating.

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The chassis is painted for rust protection. It was almost certainly brought into the assembly plant from an external supplier, in the same way as a floppy drive or CRT tube. It was probably dipped rather than sprayed -- if you were spraying it seriously, you would perform a second pass to cover the rounded corners properly.

Having looked at a few photos of naked compact Macs, I am impressed at how little steel is inside them.

I did find it interesting that the label recommends "warm to hot water" (apparently to dissove the OxiClean powder). And yet they recommend rinsing in cool water. Not sure why cold is required for the rinse.

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Are you trying to wash your colored laundry or restore your Mac? LOL

The manufacturer is covering its ass. Cold water will not cause colors to bleed or set as badly as warm water. If there is any bleed, the cold water rinse will help prevent any bleed from setting and prevent further bleed to transfer to other garments which the dryer would then permanently set. H202 is commercially used to encourage the setting of dyes in a new garment, thus a similar situation could occur in your laundry. None of this of course is a concern with your Mac, unless of course you throw your MacTV in the same bucket as your SE/30. :beige:

Lumpy, now I'm up against yet another hurdle. In all my 14.5 years of living here in Japan, I've never actually had the need to purchase H202. I know how the English translates into the Japanese (3% H202 sells under the brand name "Oxydol"), but most of the over the counter 3% solution products in 500ml sizes are priced higher than your US$2/bottle perhaps because the ingredients are different that what you have there in the US. The Oxitol I've seen contains ingredients like Phenacetin (pain killer) and either Ethanol or Phosphoric acid (the latter being more expensive than the Ethanol versions). What are the exact ingredients in the H202 you used? My guess is 3% H202 and 97% water, but I cannot find anything that basic here in Japan. All the Japanese stuff has other ingredients in it.

I've Googled up some H202 in the US and I see that when purchased in a case of 12 or 24 bottles, each bottle can be fetched for about US$1 each. However, stupid USPS no longer offers ocean shipping anymore, and it makes no economic sense to have a family member ship me 24 0.5L bottles of the stuff by AIR. Some of you here are Australian. Does Australia Post offer overseas ocean shipping? If so, is 3% H202 (97% water, no other ingredients) economically priced in case form like it is in the US?

The longer I live here in Japan, the more I shake my head at what we DON'T have here. We don't have even basic things like Cheerios or Raisin Bran cereal for crying out loud. So I'm not surprised we don't have basic, cheap H202 like in the US.