68kMLA Classic Interface
This is a version of the 68kMLA forums for viewing on your favorite old mac. Visitors on modern platforms may prefer the main site.
| Click here to select a new forum. | |
| anyone have a //c power supply and multimeter? | |
| Posted by: Osgeld on 2010-04-07 17:05:29 kinda looking at my //c, it sometimes has boot issues and i have never seen the video pop up, starting with its brick on a leash I thought I would check its output it says its putting out 15 volts, and since it is not a regulated supply (that happens inside the computer) when there is no load on it, it will naturally float up happens on all non regulated supplies, 12 becomes 14, 5 becomes 9 etc, on this supply i am getting just a shade over 19v with no load attached to it, and while this sounds a tad high, it does not sound outrageous so if anyone has a //c brick, a multimeter, and a couple spare moments to help me verify this, it would be appreciated thanks | |
| Posted by: Osgeld on 2010-04-07 20:17:02 never mind I tore it apart, looked it over and fixed a couple minor issues, it post's but has no video disk or keyboard function, obvious signs were a corroded pin on the power regulator unit which was cleaned and tinned, but there is 2 green sips with lumpy epoxy dipped packages, both have heavy corrosion, and BS generic part numbers, one is right next to the "rgb" output which actually outputs everything BUT rgb, the other is directly after the power regulator my best guess to what these things are and how to replace them is to scower the parts reference in the manual this machine is a A2S4000, with basically boils down to power problems tween these two similar components, everything else in the machine is pristine, severe yellow, but ... TN, late July the sun is like a death ray + retroBrite (and while I am at it the 2 compacts I got today too!) yes I need to replace the E-caps but none of them show physical signs of failure, in fact they are quite well made, tho I cant test them without power, and I would rather get it to boot before dumping $$ on caps | |
| Posted by: Osgeld on 2010-04-18 00:17:48 So I sat down and fixed this thing, those mysterious green sips are house branded IC's which meant if they were toast the machines functionality would be lost without becoming a parts house, they are mostly integrated op amp subsystems Luckily, the one near the power supply deals with audio and after "stuff" was cleaned up, and a inspection with a magnifying glass showed no issues, and it has no sound issues from the internal speaker or the headphone jack other than a dirty volume pot (she crackles a little) the sip near the video outputs showed heavy corrosion and green crystal growth, and was my main suspect from first opening the machine Initial tests / fixes from the last post include
today I traced the composite output back to this nasty looking area on the motherboard, and it was not making a connection with the IC, looking under magnification the trace was well beyond broken, pcb repair is needed! now I could shotgun it, and try to fix dirty, nasty, corroded, eaten though traces blind, or do it right, so I did it right, first step is to carefully remove components in the effected area for cleanup, in this case it was only the sip ic, and a resistor style packaged inductor, In this first pic the sip is already removed, the best way on this board is with a fine tipped soldering iron (+-25 watts), soldering wick and patience, these boards are soldered on both sides and in between also so it takes a few extra seconds   there is some obvious damage, but that is not all of it, corrosion causes solder mask to blister up and become brittle, and corrosion can hide broken traces in the above images you can kinda sorta guess where broken traces are, but to clean up the mess, what I did was to take a small square of scowering pad that fit the end of my index finger and (lightly) scrubbed the area. This removes all blistered solder mask and removes corrosion, and makes broken traces really easy to find  note: do not force stuff to come off, If it needs to be removed it will happen with little effort Now instead of guessing where stuff is broken or exposed you can plainly see it, starting from the left of the 10 holes in a row ... pin 3, pin 7, and pin 9 traces are broken, the remaining copper has been exposed to air for a while, which is the reason the other pins vanished over time, to keep them in line we either need to re coat them in pcb mask paint, which I do not have, or tin them with solder Get your iron, and some solder wick, heat both up and add some solder, move it onto the board and do a hot mop around all of the exposed copper(if you have ever owned a asphalt/tarmac driveway you may know the large scale idea). This will leave a CRAP ton of half burned flux goo, which you need to clean up with alcohol, but it will also place a thin top "sealant" coat of solder on top of your copper traces Finally replace the components after cleaning their leads   so we have exposed broken leads, retinned the coper traces exposed, but what about repairing the broken leads? I used a multimeter to trace paths, in this case there are 3 broken paths, all of the broken paths on this board eventually lead to a via, which sends the connection to the back side of the board, using ribbon cable segments its fairly easy to reconnect, using my photos, notes, and connectivity probing ... although probing 2 sides of a large pcb is less than graceful   moment of truth, I hooked up the mobo to power and video (leading to a pc with a tv tuner card) flipped the switch and got a classic OH SHI! WTF screen from the confused + naked machine   once set back in its case, with the disk drive and keyboard in place I got a proper response, and even entered in some applesoft example scripts      | |
| Posted by: Osgeld on 2010-05-09 18:36:03 Since this weekend my was booked solid (graduation party, and mothers day stuff) I took Monday off, and WAS going to Retr0brite my apple //c, then looked at the weather and saw it was going to be "overcast and 40% chance of rain" Great, so ... since I was running around like a madman today anyway I went ahead and did it, if you look at the last picture in the post above I am still trying to discribe its yellow, ... maybe mayonnaise mixed with plain yellow mustard?? Also I wanted to see how well the "drugstore" 3% mix would work on a machine so badly yellowed. few weeks ago I hit up "dollar tree" (a store that every thing is only 1$, hit and miss goldmine) and got 6 1 litre bottles of 3% hydrogen peroxide and a half pound tub of "LA's totally AWESOME Oxy booster", I love that store last night after my friends graduation dinner I soaked the case in warm water with regular dish soap, then scrubbed it with a nylon dish brush, that alone made the case nearly a shade lighter + it removes the question of "is that 25 year old coffee spit, or 25 year old flu snot?" from the keyboard today I got up a little earlier and cleaned a couple clear plastic bins out, and made my mix which ended up being 3 bottles of3% hp, with 1, 4 gallon office waste can (clean) of water + 1 scoop of oxy per each bin, it took 2 of my bins to lay everything out http://www.sterilite.com/ProductDetail.html?ProductId=409&Section=Storage and the results! after 8 hours still a hint of yellow on the worst places, but dramatically better, and due to constant stiring, flipping and poking, everything is very even in between the different case pieces, the parts are uniform with no splotches etc and no damage to the print on the case Over all I am very happy with the 3% mix, and while it did not get every single bit of yellow off of this really bad case the first time, it was well worth the little (but lets face it, hand scrubbing keys is tedious) effort, and the questions from my dad when I went to check my grill 🙂)  ps: yes all the keys match now, Ill post a assembled pic when its had a chance to fully dry out | |
Posted by: Osgeld on 2010-05-11 19:50:10  -- fuzzy sorry  | |
| Posted by: Paralel on 2010-05-12 06:35:10 I never realized they were supposed to be white. I've only ever seen yellow ones. | |
| Posted by: Osgeld on 2010-05-12 07:34:26 earlier ones are "snow white" later ones are platinum like the macs of the same era (later 80's) | |
| Posted by: Anonymous Freak on 2010-05-12 12:28:21 It had been my understanding that all //c's are "Show White", and all //c+'s are Platinum. | |
| Posted by: Osgeld on 2010-05-12 12:42:22 could be, Idunno | |
| Posted by: Scott Baret on 2010-06-02 04:12:00 The "snow white" color (not to be confused with the "snow" color used on iMac G3s) was, as I recall, named for a design language of the same name (in which all the products had codenames of the dwarfs--read the old AppleDesign book for more on this). The color was used only on a few products, all of which were produced in the mid-1980s: -Original Apple IIc (platinum came about with the IIc+) -UniDisk 3.5" drive -Mouse IIc (which has a more recessed button than the other serial mice and is uniform in color) -Disk IIc (a 5.25" drive) -ImageWriter IIs produced in 1985-1986 It looked as though some of the prototype Macs were in this color as well, such a BigMac and BabyMac. The Cassie Keyboard prototype was also white. | |
| Posted by: ppuskari on 2010-06-04 19:21:44 OMG - I am already a huge believer in the power of H202 but this makes me want to disassemble and RetroBrite a few soldiers in my collection. I have two of the white ImageWriter II s that should clean up quite nicely. Would love to get the Platinum back on a sentimental IIGS as well. AWESOME job you did there! Congrats! | |
| 1 |