Apple II Plus logic board troubleshooting

[Amardeep-AC9MF]

I'm troubleshooting a II Plus board from an ill-treated and poorly stored machine. I get question marks on the screen and a few clicks from the speaker instead of a beep. So far the following has been done:

1. Power supply tested good, all voltage rails within a couple of percent of spec.
2. CPU tested good in another machine.
3. RAM tested in another machine (not thoroughly but it gets to Applesoft prompt when in first row). A couple were not working but scraping the pins got them to work.
4. ROMs were pretty jankety. Corroded and broken pins.
5. Removed dirt, dust, debris and cleaned bugs and buildup under bigger sockets.
6. Completely disassembled keyboard to remove cruft and what looked like a soda spill. No strobe coming from keypresses and logic probe not seeing any columng/row scanning activity so the keyboard controller might be dead. Will deal with this separately.
7. Power supply is early model without X-filter capacitors.

So my question: Instead of pulling all six ROMs from my good machine, will a II plus come up to any useful degree (to indicate logic board is working) with just the autostart F8 ROM installed?

Thanks,
Amardeep

 

[VeryVon]

I'm sure someone on the forum with deeper knowledge of Apple ][ ROMS could comment in much more detail, and I would say go for it. If you get a beep and monitor prompt, non-garbled video on an apple 2 goes a long way to proving much of the guts of the logic board are working due to the chip-saving architecture of woz.

This seems to confirm your theory as well:

Which ROMS are needed in the Apple II / II+ for machine to function | Applefritter

www.applefritter.com

 

[Amardeep-AC9MF]

Thank you. I ended up removing all but the F8 from a good machine and it started in the monitor. Then I tried the dead machine's F8 in the good machine and it doesn't work...so the ROM is bad. But the good ROM won't work in the 'bad' machine so something else was wrong, too. Some chips had corrosion so I pulled everything and scrubbed the pins. Lost a few pins in the process since they had disintegrated so replaced a couple of parts. Still didn't work so I started systematically from near the power input and started testing all the 74LS logic parts with a TL-866. Very early I found the 74LS139 near the F8 ROM was not working. Replaced that and the board is now working. Success!