looks like a ROM 0.

there's some surface rust to clean up.

these RIFA capacitors will need to come out. they're just waiting to go up in smoke at this point.

many of the electrolytics have also gone bad.

ooh yeah the RIFA caps were on the verge of failure

need to fix up some Apple 3.5 drives.

the feet come off easily on these drives. maybe I'll try printing replacements with TPU.

something's not right! actually it's very common for stuff from ewaste to be missing any captive cables. those get cut off for copper scrap and to prevent items from tangling. engineers: please don't design products with captive cables!

this'll need cleaning and lubrication. probably also a new eject gear.

yeah that gear is basically a nilla wafer at this point

good thing you can just 3D print a replacement gear.

going back to the IIgs enclosure, i'm soaking it in Evapo-rust to clean it up. i don't have enough to dunk the whole thing...

I hate working on AC power supplies. this one seems to have issues with the bootstrap.

welp, the bootstrap resistor is open circuit! it should be 100K. the main power transistor (NPN BJT) is in the background, a Motorola 20595. pin 1 is the base, 2 is the collector, and 3 is the emitter.

well that was the problem. it powers up and provides 5V into a 1A load. (the big ceramic resistor is something I bodged as a way to discharge the input reservoir capacitors). it chirps pretty loudly during power on, not sure what's up with that.

this power supply needs an initial "kick" to get voltages to appear in a bunch of places that bias up the oscillator and power transistor drive circuit. the 100k resistor (circled) provides that.

load testing. this thing really needs a minimum load on the 5V rail otherwise the 12V rail misbehaves.

for the curious, the power supply schematic can be found here: http://www.appleiioz.com/AppleIIoz/Projects/Entries/2016/10/9_240V_Dyna_Comp_PSU_Circuit_Diagram_files/Dynacomp%20A2E%20Schematic.pdf. minor differences: it shows Q1 as a MOSFET when it is actually an NPN BJT.

made a little video adapter. this should work with my NEC Multisync (original).

well, we have video output! just need to get the drives connected, but i'll need to get my hands on some DB-19 cables first.

got a cable installed in the drive so now I'm bootstrapping ADTPro. it boots over the serial port, but then I write it to a disk to save time

thinking about how to upgrade the ROM 00 to ROM 01, i noticed that some (but not all) 27C1000 chips have the OE# input on pin 2 rather than on pin 24. this means that i could fit this 32 pin chip in the 28 pin ROM socket and let pins 1, 2, 31, and 32 hang off the end, and the remaining pins match 1:1!

i found an MBM27C1000 in my stash which has the pin 2 OE#, so it's time to program it up. it takes around 5 minutes so it is quite slow to program.

Pins 1, 32, 31, and 30 are tied together (5V) and pin 2 (OE#) is tied to pin 16 (GND).

it fits in the socket very cleanly. using the "stacked sockets" approach can interfere with some expansion cards.