This has an unusual modification which makes it do the same as a MX-949 adaptor - sort of. The adapter is mounted over sockets A, B, C & D and connects through E. A-D (4, 5, 6 & 7 pin) are not available for use. The MX-949 booklet in the cover does not list all the tubes it can test. The Gilardetti spreadsheet you can find online lists many more types that can be tested than the booklet does. With the adapter it is not suitable for testing early radio type tubes. The grey crackle on the case looks like it was done fairly recently. The 83 is replaced with solid state. Recently calibrated and working well for what it does test. The switch style of the mod is sort of putzy to use. Not a good tester if you\'re trying to test a lot at once where you would need to frequently change the settings.

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