18-11-2025, 04:00 PM
SOT = select on test. Nominally 5M to make up the total to 500M. I have a dim memory of how I calibrated it when I first built it. I had access to a DVM that went up to 1kV and a stabilised PSU that went to more than 1kV. I set exactly 1kV on the PSU and used a small resistor, possibly 4K7, at the "cold" end of the resistor chain as a potential divider. Then used the DVM to measure the voltage across that. The rest was simple arithmetic.
That sort of testgear was fairly exotic in 1974. But I was working in a professional lab with lots of nice kit. For example HP180 series scopes, which seemed to be the preferred type, rather than the solid state Teks of that era (465?). When I went to Imperial College in 1975 I was rather disappointed to find very mediocre scopes etc in the labs. Elderly Telequipment etc.
That sort of testgear was fairly exotic in 1974. But I was working in a professional lab with lots of nice kit. For example HP180 series scopes, which seemed to be the preferred type, rather than the solid state Teks of that era (465?). When I went to Imperial College in 1975 I was rather disappointed to find very mediocre scopes etc in the labs. Elderly Telequipment etc.
www.borinsky.co.uk Jeffrey Borinsky www.becg.tv
