You really just need to find one working board, then you can use an actual program to test the others.
Now, I don't actually own an IMSAI, but I've used a front panel before -- some old PDP system, I believe (played with it at a display). I found a high-res pic of the IMSAI 8080 front panel, and that's what I'll be going off of. Just keep in mind I've never actually used an IMSAI! (but if anyone wants to send me one or the CP-A card, I'd be happy to write a guide to the front panel!)
A note: 0x is the prefix I use for hex data. 0b is the prefix I use for binary data.
First off, we're going to see if our RAM board is at all functional by depositing a single byte and then recalling it. Turn on the IMSAI with the CPU card, CP-A front panel and NO RAM BOARD INSTALLED. Push the RUN/STOP switch down to STOP. Push the RESET/EXT. CLR switch up to reset the machine. Set the address toggle switches to all off (all 16 down). Push the EXAMINE/EXAMINE NEXT up toward EXAMINE. The ADDRESS BUS LEDs should all go out to represent address 0x0000. The DATA BUS LEDs will display whatever exists at that address...the DATA BUS LEDs will be either all on or all off. Remember which they are, as this is the condition of the data bus without a RAM board.
Turn off the IMSAI, insert your RAM board jumpered for 0x0000, power on, and reset. Repeat the process of examining address 0x0000: there should be a bit pattern there that's different from what you saw without a RAM board installed. If it's not, you have a problem with your RAM board...either jumper settings or a fault. If you do see something there, or just to double-check even if you don't, set the ADDRESS-DATA switches to 0b10101010 and push the DEPOSIT/DEPOSIT NEXT switch up toward DEPOSIT. The DATA BUS LEDs should now display 0b10101010. If it does, RESET the IMSAI, and examine 0x0000 again: it should still contain 0b10101010. If it doesn't, there's a problem with your RAM board: if it contains the value originally observed when you first powered on and EXAMINEd 0x0000, it may be write-protected. If not, but the data is still different, you may have a stuck bit somewhere.
As long as that works, you know your first position in RAM is alright. You should then set the ADDRESS-DATA switches to 0x10101010 again, and press DEPOSIT. Now press DEPOSIT NEXT, and the ADDRESS BUS LEDs should increment by one (they should now display 0x0001). Do this a number of times, and then reset the IMSAI. EXAMINE 0x0000 again, and press EXAMINE NEXT to make sure 0b10101010 has been loaded. You can continue this for the entirety of the RAM board, but that's tedious! Verifying a few dozen bytes at the beginning of RAM will be enough to let you get started with further testing.
The next test is a simple HALT test. Reset the IMSAI, EXAMINE 0x0000, and then DEPOSIT 0x76 (0b01110110). 0x76 is the opcode to HALT the 8080. Press the RUN/STOP switch up to RUN, and the processor should HALT (does the HLTA/WAIT/etc LED light for this? Someone with experience might enlighten us). The RUN LED should stay off. If this works, your 8080 is reading from RAM and HALTing correctly.
The next test is a little more complex. We'll load some opcodes into RAM that will output something on the PROGRAMMED OUTPUT port, 0xFF. Reset, STOP, et c., and follow these:
EXAMINE 0x0000
DEPOSIT 0b00111110
DEPOSIT NEXT 0b10101010
DEPOSIT NEXT 0b11010011
DEPOSIT NEXT 0b11111111
DEPOSIT NEXT 0b01110110
EXAMINE 0x0000
RUN
0b10101010 should show up on the PROGRAMMED OUTPUT LEDs. If it does, your IMSAI is probably in working condition!