[cctalk] Re: Identifying This Component from VT100 Monitor Board

I somehow thought that you had another board with two TO-220 packages on it or had seen a picture of one or something like that. If there is a possibility that a previous owner has been fitting random components in an attempt to get it to work, I'm inclined to agree with Tony and Holm here and suggest the correct component to fit is a BU407(D) or the BU508D suggested by Holm. It looks likely CR406 is supposed to be a two terminal diode, not a TO-3 package and this component is not required if the transistor at Q414 has an integral diode. As Holm alluded to, the board could have been designed to accept either TO-220 or a TO-3 packages in the Q414 position. Even if you received it with a TO-3 package present in this position, this doesn't mean it left the factory like that, especially if the solder joints didn't look original. Its looking increasingly likely to me that the B411 components do not belong there, whatever they are and I would suggest forgetting about trying to figure out what they are and just get rid of them. I don't think it is in any way likely that some VT100s have a BU407 in the Q414 position and others have a germanium PNP transistor in the same position with the same component reference. If you don't have another VT100 board to look at, maybe you could ask someone else to look at theirs and see what is in the Q414 position? I doubt the component varies significantly between VT100 versions unless the board was changed really drastically and if that were the case, the component reference numbers would have changed. (I don't have any VT100s) Unfortunately, if you do fit a BU407 or a BU508D, the terminal might still not work as whoever worked on it previously may have failed to identify the original source of the failure. Did the terminal ever work since you got it? Regards, Peter Coghlan.