661 Vertical Test Load Unit
The 661 Vertical Test Load Unit is a plug-in for testing the power supplies and interconnections in a Tektronix 661 sampling scope. It serves a similar purpose to the TU-4 (for the 560-series) and 1M1 (for the 500-series). It contains load resistors for testing the mainframe's power supply. It also contains a switch for testing the wiring between the plug-in interface and the multi-pin digital output connector on the rear of the 661 mainframe. There is a banana connector on the front of the plug-in that is wired to the +300 V pin on the interface connector via a fuse.
