I purchased and built a Heathkit IO-4225 scope in the mid 80s and after it had been "updated" a couple of times at the Local Heathkit store it worked flawlessly for quite a few years. When I no longer needed it found itself in the attic for a number of years. I recently rescued it from it's exile and found that it no longer worked - imagine that. When turned on there is a trace until it warms up a few minutes then the trace goes away. I have looked for my manual and I fear that it was lost during a move and the "new" Heathkit web site does not list one. Apparently this is a somewhat "scarce" model being the last O-scope they put out before going under. If anybody has one I would be eternally grateful!