The IO-104 laboratory class 15MHz bandwidth triggered-sweep oscilloscope came on the market in 1973 and was produced until 1975. The IO-100 series of solid-state oscilloscopes consisted of the IO-101, IO-102, IO-103, IO-104 and IO-105. The IO-101 was a vetcorscope but the other were ordinary oscilloscopes, where the IO-105 was dual-trace. The IO-102 was a general purpose single-trace 5MHz oscilloscope that came on the market in 1971 and was produced until 1975. It replaced the IO-18 and the IO-18U*, that in turn had replaced the IO-12 and the IO-12U*. The IO-103 was a laboratory class 10MHz triggered-sweep oscilloscope that came on the market in 1972 and was produced until 1974. The IO-105 was a dual-trace version of the IO-104. The IO-105 came on the market in 1971 and was produced until 1974. The IO-100 series was replaced by the IO-4000 series in 1975.

*The British Heathkit factory in Gloucester produced several kits with the letter U added to the designation. Among them was the IO-12U and the IO-18U. The U meant The United Kingdom. The IO-18U differed from the IO-18 in terms of a slightly modernized style like the rectangular CRT.


My IO-104 had not been used for a long time when a friend bought it for me at a Hamfest flea-market. The controls were sluggish and the scope was way off decent accuracy. I had to clean it and recalibrate it. Now it works like a charm. It has quite some temperature drift though. It has to be turned on for at least half an hour before making any accurate measurements.