I think I have got my VT100 basically working now except for the actual video display. I think there is a problem with the transistor that drives the flyback transformer. This is Q414 on page 58 of the Feb82 schematic on BitSavers (https://bitsavers.org/pdf/dec/terminal/vt100/MP00633_VT100_Schematic_Feb82. pdf). I have removed it from the circuit and tested it with the diode tester of my multimeter. It does not test as two diodes, indeed across Collector-Base the multimeter beeps for a short circuit, and so I am fairly sure it is bad, The part is the one with the heatsink as shown in this picture: https://rjarratt.files.wordpress.com/2023/12/img_20231221_112305.jpg. I have found some information on it here: https://www.web-bcs.com/transistor/tc/b0/B411.php but the Feb82 schematic shows it is a BU407D. My video board is not exactly the same as the one in the schematic despite having the same DEC part number, but the circuit that drives the flyback is the same on the secondary side of T403, and includes the optional diode CR406 in the form of another B411 transistor that is not connected at the emitter. I am trying to identify a replacement and could do with some help identifying one. I can't find a full datasheet for the B411, all I can find is this https://www.web-bcs.com/transistor/tc/b0/B411.php, which seems to match the part I need to replace, and I have also found one for a BU407 (not BU407D) here https://www.mouser.co.uk/datasheet/2/308/1/BU407_D-2310257.pdf. I have tried to find something that meets or exceeds the voltage, current and switching time specs. I have found a couple of possible replacements and would welcome opinions on their suitability: https://www.farnell.com/datasheets/2861437.pdf and https://www.farnell.com/datasheets/3033460.pdf (assuming that the switching times are a typo and they are in microseconds rather than seconds) Do these seem like suitable replacements? Thanks Rob