Later Hickok tube testers with a few exceptions marked the rise of the transistor. Testers became more and more decontented and aimed at a lower priced market. Some had more features but the Cardomatics had shown that simpler devices were desirable.
The followon 800 series was really an updated 600 with some 6000 features. Testing of Compactrons was added making the "A" series probably the best easily portable unit made. This was also the last example to be introduced using the trraditional two tube Hickok circuit, future untits were either transistorized or had no active components (230).
There are three varients of the 800 known: original 800, 800A, and the 800K which carried the odd-sounding legend "Wired as a 600". They are easily recognized by the sockets: 800K has a single horizontal row, 800 has two vertical sockets by the meter, and the 800A has three vertical sockets. The only reason I can think of for the K is that some servicemen were slow learners.
The next new tester that Hickok introduced was the transisorized model 799 "Mustang". This was a return to the drug store many sockets/few knobs style but was still a full Dynamic Mutual Conductance Tester. Also unlike most earlier Hickoks, full calibration capability is provided by five potentiometers located under the access panel at the lower right.
This access panel could also be replaced with the CA-99 Adapter panel which added a number of additional sockets and settings.Note that while there are "only" 37 sockets compared to the incredible 63 provided in two paneld by a contemporary B&K model, the Hickok provides three different settings for each socket, providing over a hundred different configurations.
Hovever the 799 is not quite as exhaustive a tester as earlier Gm units, it tests all tubes as triodes.
With a retail price of $199.95, the same as the model 800 that it replaced, the 799 was not a cheap tester as examination of the craftmanship evidences.
During the '60s, Hickok attemped a number of "low cost" testers oriented to the hobbyist. The rather simple but very portable 820 was one of these. The simple front panel makes it evident that this is at best an emissions teter but is more probably just a continuity/shorts check.
The final tester in this group is far from the least: it is probably the closest thing to a modern laboratory quality tube tester Hickok ever made. Fully transistorized, the model 580 is rarely seen yet was intended to replace the 752A which in turn was intended to replace the 539 at the top of the Hickok lineup.