Hi Guys,
I'm working on a restoration of a TDS540 with all the usual problems. It also has a not very clean square wave on the calibration signal, so have been looking at the front panel board to try and sort it.
But, either I'm being a numpty and not looking at this right, or the board I have is a different version to what the schematics show, but I have not been able to find any other schematics. So can anyone with experience of the 540 help me out here?
I've uploaded some photos to an album called TDS540 Front Panel (is that the right way to do this?). It shows the part of the schematic with the cal signal output coming from Q1, and a shot of the board (with the two screw heads) that is clearly quite different; the collector of Q8 is connected directly to the output.
The other issue is that C12 (in the other shot) has no volts across it. So is it missing a supply rail, or is this just a signal cap? Without the correct schematic it is a little tricky to figure out.
Thanks a lot,
Ralph
RJ