560-series scopes

The 560 series scopes which were introduced with the 560 and 561 in 1961 were tube scopes that began to introduce some solid state circuitry.

They use 2-series or 3-series vertical plug-ins and 2-series or 3-series horizontal plug-ins (exception: 560 only takes 2-series because of weak power supply).

560-series mainframes contain no amplifier stages, requiring the plug-ins to drive the CRT deflection plates directly. While promoted by Tek as having the advantage of “not limited by additional circuitry between the plug-in and the deflection plates”, this configuration has a significant disadvantage in that when swapping plug-ins, gain or sweep have to be calibrated.

In scopes with amplifiers in the mainframe, touching up the gain or sweep cal when swapping plug-ins can be skipped, as doing so only tunes the accuracy to a small amount of additional precision. In the 560 series however, this step is required to even get crude accuracy, as the raw deflection factor of the CRT has a relatively large range, and the mainframe has no circuitry to normalize it.

To maintain good phase match over a wide range of frequency, the mainframe does not contain a delay line in the vertical path. The faster vertical plug-ins contain the delay line, which limits the available volume for amplifier circuitry.