This Tektronix 7704A sn 102137 was my shop workhorse for a few years. Last year I plugged it in and fired it up, and a cloud of white smoke poured out of the vents on the rear side. I took it apart and couldn’t find any visual evidence of the damage. I think it was a filter cap in the PSU that went to Dead Cap Heaven. I was astonished that the power supply was so small. I never got around to actually attempting a fix yet. This mainframe scope has 4 slots for plugins. The upper and lower halves both have the same serial number.

The Users Manual link is: https://www.dropbox.com/s/ighextucke20jt1/Tek7704A-op.pdf?dl=0

The Service Manual is very large, and its link is: https://www.dropbox.com/s/gmsgmhs6jn4jsig/tek-7704a.pdf?dl=0

Let me know if you have any stories about the Tektronix 7704A Oscilloscope System, or are interested in buying mine at a reasonable offer.