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Oh, good idea. I actually used your webpage to pick the SST flash parts in the first place, because the other replacements weren't carried by Digikey. I also picked the IIcx EPROM replacement with help from that page, so it's already been incredibly helpful. I don't personally mind bodges in...

I got a TL866II Plus, which was pretty affordable and works great in Windows VMs. I considered a Relatively Universal ROM Programmer as well, but my Arduino is currently serving as a Nintendo 64 Joybus to USB adapter, and the thought of having to adjust a trimpot to control programming voltages...

Yes, and the relevant part of the datasheet (which I completely missed) supports this. OE has to be low input and WE high to read. Vice versa during erasing and flashing. Since I used a normal OTP/windowless EPROM for the IIcx ROM repair on the same day, this one difference with the flash chips...

Oops, sorry if I forgot to clarify this, me mucking with ROMs just to get stock ones must've sounded pretty silly in the OP. I was using a ROMinator this entire time because there was a fault in the mask ROMs in my otherwise fully functional IIci. I've been trying to get the machine's built-in...

Recently, I ordered four SST39SF010A chips and flashed them with the correct four parts of the Mac IIci stock ROM (DWORD bytes 1,2,3,4 interleaved). I inserted them to my sockets in the correct orientation and order, powered on the IIci, and got the normal speaker pop with no chimes or any...

Final(?) update, and hopefully with enough time in between for replying to myself not to be spammy. I finally bit the bullet and bought a universal ROM flasher/programmer, so after coming a long way, my IIcx has closure! The flashing software was featureful enough to load the second bytes out...

Managed to ruin the ends of three traces while removing dead mask ROMs, only on the final chip. Everything was going smoothly until the last possible moment. At least the bodge wires will end up snugly pinned beneath the DIP socket, but it'll be weeks before I forgive myself for blemishing such...

This brings to mind another riser/Twinspark quirk that made me uneasy, the EMI near that top card... Ever put your hand near the anode cap while wearing headphones? BZZZZT.

Seconding most of what's been said, I have a DiiMO 030 and a TwinSpark, but have since removed them. DiiMO's a perfect fit for my recently-revived IIci, but that TwinSpark is just an expensive egg on my face. It was a huge improvement, sure, but without color and 640x480, I eventually regretted...

My "new" IIci's soft power was stuck always signaling on, but I found the three micro-breaks in the relevant traces. Wish I'd spotted them during the board washing, but oh well. Humorously, both could've been fixed by simply bridging pins, but I wanted to make this look as elegant as I could, so...

Do you have a bench power supply of any kind? ATX->10pin adapter? I'd second the PSU suggestion, and test with a known good one, just to quickly confirm whether the PSU has the fault.

Got a hold of a cheap IIci and made the logic board sparkle again. Lifted dull-looking chips, cleaned the legs and pads, drag-soldered back fresh. Nice new caps, no broken traces in the acid zones, power circuit works. However, either the ROMSEL circuit or the ROM chips themselves are again bad...

You are not going to enjoy hearing this, but I found the break in the circuit, at least on mine. It was between R33 and C107+C105 (back side.) I did this IIsi in 2017 or so, before I was anywhere near as good at neutralizing and washing PCBs, and some residual electrolyte was trapped in my...

I have this as well on my good IIsi. I have a broken motherboard where this circuit works as intended, but the test pads near the oscillator and the MCU do not have a pulse on the good board. I've been checking continuity, resistances, hertz, etc for hours and would be curious to know if anyone...

It looks so beautiful that I'm already dying to see someone talented at drag-soldering put one together. These things always make a great visual aid to schematics, and seeing as you've gone back and patched the Bomarc ones, it's a win-win. Whether someone needs bodges and trace repair or a brand...