On 07/06/2020 18:27, Charles via cctalk wrote: > Until a few minutes ago, my VT240 was operating normally, but now it's > unresponsive (fails during power-on self test). > > Normal behavior was: display a checkerboard, then two different > intensity all-white bands growing slowly up from the bottom of the > screen, then a beep and the expected "VT240 Monitor Error 9" (because > I'm using an old B&W composite monitor instead of the DEC VR201 with > special cable). Thereafter, normal operation. > > Now, it briefly displays the checkerboard (and all four keyboard > lights turn on, then off); then the Lock and Wait lights come on and > nothing else happens. Blank screen. >
The keyboard LEDs are used to indicate the test being performed, in this case test 5 failed. They are listed in the pocket service guide. For the first 6 codes it just says fatal error, replace terminal controller board. I don't think it is the keyboard. You should get an error code 7 on screen for that. I'm afraid I haven't looked into the VT240 firmware but I have looked at the VT220 previously. Here are some of my notes on the self test: 0 = 8051 Internal RAM Test (Data=0xAA) 0 = 8051 Internal RAM Test (Data=0x55) 0 = 8051 Internal RAM Test (Data=0x00) 1 = 8051 Internal ROM Checksum (8840: lcall $8870) 2 = External ROM Checksum 0x8000 (884B: lcall $8870) 3 = External ROM Checksum 0xC000 8 = Screen RAM 0 (Addr=0xA000 Data=0xAA) 9 = Screen RAM 1 (Addr=0xA800 Data=0xAA) A = Atrrib RAM 0 (Addr=0x8000 Data=0xAA) B = Attrib RAM 1 (Addr=0x8800 Data=0xAA) 8 = Screen RAM 0 (Addr=0xA000 Data=0x55) 9 = Screen RAM 1 (Addr=0xA800 Data=0x55) A = Atrrib RAM 0 (Addr=0x8000 Data=0x55) B = Attrib RAM 1 (Addr=0x8800 Data=0x55) 8 = Screen RAM 0 (Addr=0xA000 Data=??) 9 = Screen RAM 1 (Addr=0xA800 Data=??) A = Atrrib RAM 0 (Addr=0x8000 Data=??) B = Attrib RAM 1 (Addr=0x8800 Data=??) C = Character ROM (read only) D = Alt Character RAM (read/write) E = Alt Character RAM (?) I know the VT240 uses a different processor to the VT220 but this gives you an idea of the sort of things that are being tested early on. I imagine the VT240 will carry out a similar set of tests. Matt
