513
The Tektronix 513 is a single-channel monolithic oscilloscope with 18MHz bandwidth. The input impedance is 1M-ohm in parallel with 40pF. It provides power to an optional cathode-follower probe. The 513D has a delay line; the 513 does not. The 513 (and 513D) contains a distributed vertical output amplifier made of 6CB6 tubes.