The Tektronix 515 is a 15 MHz single-trace all-tube oscilloscope introduced in 1955. It does not use plug-ins.
A rack-mount version, the RM15 was also sold. There is also a 515A.
The HV power supply uses three 5642 rectifiers to produce +2325 V for the CRT anode and -1675 V for the CRT cathode. The LV power supply is linear, using a 6080 tube as the pass tube of the series regulator for +300 V and +100 V supply. The -150 V supply is regulated by a 6AU5 tube. The voltage reference for the -150 V supply is a 5651 tube. The 515 and 515A use selenium rectifiers. A kit was later made available for converting them to silicon rectifiers for improved reliability.
The vertical amplifier is fully differential, DC-coupled, and all tube. The stages are as follows:
- input buffer, cathode followers, 6AU6
- first gain stage, differential amplifier, T-coil, 12BY7
- unity gain buffer, cathode follower, 6DJ8
- output amplifier, differential amplifier, T-coil, 6CL6
The horizontal amplifier uses half of a 6DJ8 as a buffer, followed by a 6DJ8 as a differential amplifier and phase splitter, followed by the two halves of another 6DJ8 as the output cathode followers driving the horizontal CRT deflection plates.
The trigger is a 6DJ8 differential trigger amplifier followed by a 6DJ8 Schmitt trigger.
The 515A has a Z-axis input and slightly higher vertical sensitivity than the 515. The maximum vertical sensitivity is 100 mV/Div for the 515 and 50 mV/Div for the 515A. The 516 is essentially a dual-trace version of the 515.
Serial numbers 101 through 1000 are "Type 515". Starting with serial number 1001, they are "Type 515A".