Just purchased Mac 512k

[Charlieman]

Wally makes a few good point re RTC in this thread:

http://68kmla.org/forums/viewtopic.php?t=686

 

[CaryMG]

I forgot to mention Old SoftWare.Com as an online place to buy new-in-box & used boxmax software, too. lol

Sorry sorry for the mixup!

Once again -- the 3 online stores are ....

1] MacTreasures

2] Old SoftWare.Com

3] B & R Computer Services

:b&w:

 

[Mac128]

Wally makes a few good point re RTC in this thread:http://68kmla.org/forums/viewtopic.php?t=686

That's the one I found too. However, I don't think the problem is the same, though the solution may be. Big Bird's clock would not count normally, a problem which lumpydog does not seem to be having. His software interface seems to have a problem writing to the PRAM itself, even though it maintains other settings, even following power down. Wally does bring up some interesting points about the VIA routing signals into and out of the RTC. I don't pretend to understand the intricacies involved in the discrepancy preventing the retention of the clock setting vs. others though. Or for that matter how the PRAM chip stores data. Could it be that the chip suffers from bit-rot and the portion of the RAM where the clock settings are stored is physically inaccessible (assuming it stores specific data in a specific order like regular RAM). Does the ROM startup routine check the PRAM as well?

The fact that going through the dishwasher solved another seemingly unrelated problem, suggests that there might be something else impeding the clock settings on the board, assuming they travel different signal paths than the mouse and volume settings.

Involving only 8 pins to solder, I would think the RTC should be replaced at this point baring any other input. Perhaps just de-soldering the chip, cleaning underneath it and replacing it will be enough.

 

[JDW]

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

I've been quite curious about this since your original posting. I spoke with my father recently about that Oxiclean, and when used on clothing stains he said it "works wonders." So despite Mac128's encouragement for me to use another brand, I asked my father to send me a small tube of the stuff, as I have two small children with attire stained badly enough to warrant a dose! Plus, with Lumpydog's technique working wonders with virtually no H202 at all (less than 1.5%, from what I see), I can't help but wonder if that OxiClean isn't doing most of the job on its own.

Anyway, I've been worried about the labels because I plan to dip the chassis of my SE/30 in this miracle mixture. While not seen in any of the photos I've placed on Flickr, there is a patch of yellowing toward the back of the case, just above the analog board. It's clear that heat has caused this. I am also curious to see if the OxiClean mixture will make the entire case go back to the new platinum color UNIFORMLY. I certainly don't want to see the yellowing be reduced to the same degree in all places, leaving the machine looking spotty as it does now.

At the same time, I don't want to see my labels damaged or peel off either. And while the label on Lumpy's mouse was apparently not affected, I am curious if all labels will fair so well. I'm also curious how the gray colored paint on the inside of the compact Mac's housing will do after a few hours soaking in this mix. I don't see why labels would be completely unaffected when the Apple logo stands to be utterly destroyed as shown in the photo Lump links too. That's frightful!

I am excited about the potential from this yellow-killing mixture, but quite anxious about it too!

 

[lumpydog]

JDW:

A few comments:

1) I have experienced no collateral damage thus far. That is to say, no logos, screened on labels or serial number labels have been harmed or faded. I did remove the square Apple logo from my HD20 case by popping it out of the case (push from the hole behind it). I personally think the guys in the de-yellowing thread, that I linked to earlier, have been using WAY overkill solutions at 30-40% Hydrogen Peroxide. I'm pretty sure at the 3% to 1.5% solution that I've used, the color apple logo would have been fine without removal. The paper label on the bottom of my mouse and the serial number label on my HD20 look fine.

2) If you cant remove the logo, you might try masking tape... I have not yet tried this approach - I would not recommend it over a paper label.

3) Regarding uneven yellowing and uniformity after the process. I promise you will be amazed. My HD20 had the footprint of the Mac that sat atop it... a halo of yellow around it (see pictures). You can't find it now - no trace - zero. My mouse had some deep yellow spotting (see the pictures). No sign of it now. By the way, the pictures really don't do justice to the result.

4) The insides of the HD20 case (same finish as the Mac case) was not effected in any way that I can see.

At the diluted levels that I've used, I've seen highly effective results and no damage to innocent parts/pieces. I'm excited for someone else to try this - the results are extremely gratifying and worth the hassle to find a the H202, Oxi, a clear tub and a sunny day. It's WAY to easy and appears to be non-damaging in any way.

I'm going to do my 512K Mac case this weekend (big clear tub that I have in my attic) and will post results. I am going to just pop out the apple logo. I'll let you know how the rear plastic label and the paper serial number label fair. It will be a very diluted mix... I'll post pictures.

Lumpy

P.S. To everyone else - I'm trying to find some time to tackle the RTC issue. I have just not had time.... One thing I did notice is the the R16 (capacitor?) which is next to the RTC chip, appears to maybe be compromised. It's hard to tell because these things are so damn tiny.

 

[Mac128]

with Lumpydog's technique working wonders with virtually no H202 at all (less than 1.5%, from what I see), I can't help but wonder if that OxiClean isn't doing most of the job on its own.

As I posted earlier, Oxiclean is mostly sodium percarbonate and to a lesser degree sodium carbonate, which when combine with water, the sodium percarbonate BREAKS DOWN INTO H202!

In other words, whatever percentage of H202 is already in your liquid solution, the "Oxy" product increases it along with the PH level. So you are being mislead by only looking at the H202 percentage lumpdog uses as the Oxiclean is upping it as well. However, since others are starting with a much higher H202 percentage as well as using an "Oxy" product, lumpydog's overall solution is lower in H202, but ultimately more than indicated on the bottle. As for "doing most of the work", I would think not. Since no matter how much Oxy compound you put in water, it still won't produce as much H202 as a mixture already containing it. Plus, there is a limit to how much powder can be absorbed by the water and possible negative effects from the substantially increased soda ash in using an Oxy compound alone.

Since you already have a source for the substance, this is something of a moot observation, but most of those in the Vintagecomputing forum achieved equally amazing results to lumpydog without specifically using Oxiclean, but a generic "Oxy" product. My guess is Oxiclean happened to be the brand lumpydog had on hand (which he may answer for us). While caution is prudent in the restoration of an irreplaceable Mac, I think Oxiclean is more marketing than "magic" (appearing on direct marketing infomercials and commercials frequently here in the US). According to its website, it uses the exact same ingredients as the brand I picked up at my local supermarket (which carried half-a-dozen varieties, none of which were Oxiclean). The use of a local variety might save you a fair amount over Oxiclean's inflated price, not to mention shipping to Japan.

 

[lumpydog]

My guess is Oxiclean happened to be the brand lumpydog had on hand (which he may answer for us).

Yup! What I had on hand :beige:

Lumpy

 

[Mac128]

One thing I did notice is the the R16 (capacitor?) which is next to the RTC chip, appears to maybe be compromised. It's hard to tell because these things are so damn tiny.

C16 or R16? The C16 capacitor is the one right next to the CLK. The R16 resistor is next to the filter. C16 could definitely be a problem as it appears to be connected to the power pin -8- on the RTC chip. Since you know power from the battery is good to pin-11 on the logicboard, and your PRAM does not retain settings after restart, the backup power is likely not making it reliably into the RTC causing who knows what kind of problems. If so, it is definitely an easier fix than finding a new RTC. Could that capacitor have blown when you had the battery in backwards?

I'll let you know how the rear plastic label and the paper serial number label fair.

If your HD20 plastic & paper labels did OK, I'm sure the 512K labels will as well. I suspect the problem with the logos is that they are metal and are painted. H202 is highly corrosive to metal. That alone could account for the paint blistering due to the chemical reaction beneath it. However, the paint could be lead-based, or other susceptible base as well. Considering these as possible explanations for the damaged logo, I am actually surprised that the metal-based coating on the inside of the cases is left alone. Some aluminum is immune to H202's corrosive effects so perhaps that explains it. Anybody know the composition of the RF paint used inside the early Macs? What about the later metallic coatings in the SE?

 

[lumpydog]

Mac128 - you're correct. It was C16.... NOT R16 - thanks for asking. I was at work.

I'll need to look more closely at it this weekend. it appears to be damaged - but it's hard to tell. No burn marks, etc.

 

[lumpydog]

Ok Mac128... My multimeter says C16 on the logic board is toast (it looks it too). Everything else that I tested around the RTC (including the battery checks out).

What is the replacement part number/description for C16 on the logic board? - it is a diode... Where can I get a replacement?

Pina, in his book, does not appear to give the detail to logic boards that he gives to the analog board.

I'm hoping you might be able to provide some help/direction on getting the part to replace C16...

Lumpy

 

[JDW]

According to the BOMARC and Apple SE/30 schematics I have, the positive side of polarized capacitor C16 is connected to pin 6 of UB10 and UB11 (the Sony chips), and is also connected to R5 and R11. And the other side of R5 connects to the Reset switch. Both schematics show C16 as ".1" which I assume is 0.1uF (microFarad). C16 is found on the bottom of the logic board, nearest the two switches.

I have C16 shown in PDF form, in both schematics, hosted on Google Docs. Stupidly though, Google Docs won't let me share PDFs with everyone, so I have to manually plug in email addresses to give people individual access. PM me with your email address if you want to see my PDF.

Now with that said, I suspect your C16 may be just fine. You would likely need to remove it from the logic board to perform an accurate test anyway. C16 is a chip capacitor which, unlike the big tanks on the top side of the board, don't tend to fail over time.

 

[Mac128]

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.

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.

 

[lumpydog]

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...

 

[Mac128]

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

 

[lumpydog]

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?

 

[JDW]

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.)

 

[Mac128]

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).

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.

 

[JDW]

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]

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.

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.

 

[JDW]

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).