Hi Group,
I've got a 54540A in need of repair. This is a 4 channel 500 MHz digitizing scope of the generation before Infinium. When first turned on it appears that nothing happens. But it is alive to the degree that it recognizes if you hold down a key during power-up, which is the signal to prompt for a firmware update. In this case a prompt appears on the CRT, and you need to confirm with another keypress if you really want to read in new firmware. If I press another key (even though I don't have a new disk for it), then it appears to go dead again.
I have checked all the power supply voltages and found everything in order. My theory is that some part is failing the power up self test early in the sequence, and it is not able to display an error message at that time. HP service consisted of exchanging keyboard or main board assemblies, which would be determined by swapping in a known good one. A replacement assembly would probably be too expensive even if they had one available.
Before I write this off ... does anyone know how to access any further diagnostc info, or if there are any specific things that I could check and possibly repair to fix this ?
Geo.