I'm reading the diagnostics manual section for the A5 timebase board. The 8 LEDs, ST0-7 come on at power on and stay on while it runs through the self tests I have J710- J713 set to 0. There is never any change in the brightness of the LEDs and all the diagnostics run until it stops with an E5622 error.
I'm somewhat at a loss with regard to the divergence between the manual and the actual behavior.
There is evidence that the underside of the case got damp in the form of brownish discoloration of the external surfaces of the end frames and white powder at several points where the bottom cover touched the frames. However, there is no indication that the boards got wet. The discoloration is consistent with what I'd expect if it sat on a concrete slab for a long period of time in a non-climate controlled room. The unit came from Arizona.
I have removed and reseated all the board connectors on the A5 board except for the coaxial lines. If the other end of the A5 cables was within reach I reseated the other end also. I've also reseated the 4 ROMS in unmarked sockets next to U501 and U511. The ROMs are marked U300, U310, U400 & U410 V10.1 1991.
Instrument serial number is B030215.
