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
- removing and re-seating all IC's that were in a socket
looking for leakage / corrosion around caps
fixing corroded pin on power brick (which was just 1 of many ground pins but better safe)
scanning power lines for stable 5v going to chips
alcohol scrub down with "acid" brush (disposable horsehair plumbing flux brush)
I gave it the finger ...
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