7904 and 7A19 attenuator and vertical scale woes

Evan Geller

Hey everyone!

I've run into a few problems with my newly acquired 7904. The first seems to be an intermittent connection underneath S135. I've scoped a test signal up to J12 and everything seems happy... and specifically touching the coupler on S135 makes the signal jump. Any recommendations for cleaning under this switch without damaging anything?

My second question pertains to the on screen display. It seems to have walked off the screen a bit! My first thinking was that the CRT just wound up vertically scaled a bit... but hooking the 7A19 up to the voltage calibration shows that the voltages line up with the lines on the graticule. Is there somewhere that moves the text around on screen? If not, does this just mean that the vertical scale is off in the mainframe and someone decided to compensate by rescaling by rescaling the 7A19? That would be pretty unfortunate. I don't have an extender so I can't trivially pick off the voltages from the card. Maybe some of you have a trick for this that's more elegant than soldering kynar wire to the board and scoping that.


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