I am working on a Franklin Ace 1000 Apple ii+ clone that I picked up recently. While I have successfully repaired several other systems, I have never owned or worked on an Apple or clone system previously. Before booting it, I installed a new power supply from ReActiveMicro which seems to be working perfectly although 5v is a bit low at 4.77v. The system boots to a "garbage" screen. It generally displays a similar pattern to the first screen shot below but often there are random characters (sometimes blinking) scattered across the screen. There is no beep on boot. I will some list of the steps I have taken to try to figure out the issue after the screenshot and would greatly welcome any suggestions or wisdom.
1) Removed all ICs, put Deoxit in the sockets, and reinstalled the ICs. In the process, I found one ROM and two DRAM chips with legs bent up under the chip and not properly inserted into the socket. I fixed this plus cleaned the legs on many of the 4116 chips which appeared to be almost black although not visibly corroded in any way. I found the transister at G4 had been mashed down and a couple legs were shorted which I fixed. All of this resulted in no change.
2) Replaced all 4116 ships in the "C" row with NOS 4116 chips. No change. I had also swapped those from the "D" row into the "C" row and vice versa when I put the ICs back as a test and also no change there so I don't think bad ram in row "C" is the issue. I don't have a ram tester to be sure.
3) Tried a new 6502 processor. I did not think this was the problem but I had one so why not. No change.
4) I have a decent supply of 74LSxx(x) ICs that I tried. No change. I can supply details on this if that is helpful. I must have tried about 8 different types of 74LS ICs, some of which I tried in mutiple locations where they are used, with no change. Unfortunately, I have no way to verify the ICs I have are good although they are supposed to all be new so not sure how good a test this is. I certainly did not replace all 74LS ICs so if there are specific ones to try please let me know and I will purchase the ones I do not have.
5) I have a logic probe (but not a lot of experience using one) and I confirmed that the 6502 reset pin was high and only pulled low when I pressed the reset button with no change.
6) I removed each of the ROM chips one by one and booted replacing the last chip before pulling the next. No change except in one case that I will list below.
There are only two occassions that I noted any change to the general pattern of "garbage" I see on the screen on boot. The first was booting without any ICs in row "C" just as a test. In that case, the screen appeared very similar to the screenshot above but with only the "checkerboard" symbol in all places instead of alternating with the "@" symbol.
The other time that I noted a change was when I booted without the 2532 eeprom (maybe the character ROM? I cannot find much info on the Franklin system) that is located on the color daughterboard that fits onto the mainboard. When booting without that IC, the boot screen alternates between a completely white screen and one with alternating white and black vertical strips. It changes between the all white and the stripped screen at about one second intervals. I don't know if this indicates that the ROM is bad or whether that is just the normal behavior when it is pulled.
Thank you. All suggestions are appreciated!