Got an Apple IIe which is giving various issues - history of the machine is unknown, but apart from being dirty there appears to be no physical damage to the PCB or keyboard.
1. Refuses to boot to the on-board diagnostics - this was working and giving a SYSTEM OK message, but now ignores the Apple keys being pressed on power up
2. With a Super Serial card installed in slot 2 and typing IN#2, CTRL-A will sometimes give the 'Apple SSC:' prompt, sometimes not returning the ] prompt
3. Typing CALL -151 will usually enter the monitor, but sometimes is just ignored just going back to the ] prompt.
4. Using Freitz's SD card interface, gives his copyright message at the bottom of the screen but doesn't boot from any SD card.
The system was originally a standard IIe, but has been upgraded with a Rockwell 6502P4 CPU and the Enhanced ROM set - using a test routine from Chromatix correctly identifies the CPU as a CMOS version - the EPROMS were written and tested by Freitz so have no reason to suspect a problem with them.
It seem to boot reliabily to the Apple BASIC ] promt each time it is powered on, but Control-RESET is also ignored by the machine.
Any help, suggestions etc would be very much appreciated as I'm no Apple II expert and the knowledge I do have is old and very rusty.