I may have done something stupid but I can't seem to find exactly what. I was looking for some plugins better than what I got or at least another vertical. Right now I have two 7B50s and a 7A18N. The N stands for Nothing, it is a 7A18 without the readout. No biggie, I know how to count divisions.

My bright idea was to use this thing as a component tester but still have it easily switchable back to normal scope use. It is fast enough for most of my applications and is still bright and sharp, so why not ? It was not going to be mobile - to say the least.....

So I got me down to BAMA and got the print for the mainframe, mainly becasue I had to fix it. A couple of those forty year old filters had failed, how dare they ? I had the thing all up and running and was pleased. Then I decided on this component tester idea. I looked at the mainframe print and determined that I could indeed use a horizontal plugin as the second vertical in the right slot, just use the external input for the trace, and apply whatever waveform to the DUT. So far so good and it was actually working. I hadn't really finished, I was going to find an OPAMP or something to boost the sensitivity a bit so I could use a lower amplitude applied signal and possibly a few other refinments as I got round to it.

However the other day I go to fire the old beast up and I have no sweep. The readout for the time/div is no longer at the top, it is more toward the center. The first thing that came to my mind was that I missed something and you actually cannot use the 7B50 in a vertical slot, but neither one of them work now. Surely I didn't fry the both of them. So I figure maybe again, that I missed something and somehow wiped out one of the sources on the mainframe but they all check good, at least out of the rectifier board.

I thought fairly sure that Tek stuff wasn't like a Sony TV and it unlikely a shorted plug in would fry the power supply or anything like that, though it is not impossible.

At this point, if the problem is in the 7B50s, obviously I caused it and shame on me. If the problem is on the mainframe then it is possible that it just happened. This is what I question becasue each scenario would put me in a slightly different mode in troubleshooting old Betsy here. I know the thing isn't worth a fortune but I like it.

Between the plugins and the final horizontal amps does work because an external input will work, or at least when the selector is set to "line". In timebase mode the display is there, this tells me a few things that it is NOT..

Whaddya think ? Anyone around here ever have success using a horizontal plugin for a vertical in a 76XX ? I am sure you can go the other way to get an X/Y display (I think), but is there some reason you can't do what I did ? I checked the prints paying attention to the plugs to the plugins. If anyone cares to give them a second look they are on pages 146 of the 7603 PDF and 105 of the 7B50 respectively. I can't seem to find anything that would indicate that it was an ID ten T error. Nothing seems to point to that but I find it hard to beieve both 7B50s failed the same day for no reason. Still, when you put it in auto trigger it should be able to get a trace. It does not.

The main question here at this point is if there is simply a fault in the mainframe or if I blew it. If it "just happened", well then I know what to do. I think.....

Any ideas ?