Heathkit IO-102 PC Boards 
Heathkit IO-102 CRT and Vertical Amplifier
The Heathkit IO-102 is a transistor based oscilloscope. I replaced the electrolytic capacitors and some transistors that were very temperature sensitive and caused the unit to drift badly. This unit is used regularly on my test bench. I built one of these from a kit many years ago, but not this one.
Hi there. I just acquired the same model, and am excited to get it working. It powers on fine, but all I get is a large green dot on the screen, and not a line. I tried fiddling with all the knobs, but nothing seems to work. Do you have any pointers for me where to start looking? Thanks in advance!
Download a manual and see if that doesn’t help.
Eric,
Try setting the sync to internal and crank up the gain until you can see a horizontal sweep. You will need to connect a signal (audio from TV or stereo is a good demonstration source) to the vertical inputs to see a waveform. Also from the size of the dot you describe you probably need to adjust the focus. Manual PDF: https://archive.org/details/HeathkitIO102Manual