6R1A

The Tektronix Type 6R1A is a plug-in for the 567 oscilloscope. It replaced the 6R1. The 6R1A provides digital readout of time and voltage measurements on waveforms. The 6R1A (and the 567 in general) is oriented toward sampling measurements. The 6R1A is a counter and a comparator. To digitize analog voltages, the counter and comparator are used as a ramp-compare ADC. Card Q (Voltmeter) contains a 1MHz crystal oscillator. The counters (Card A) are made of flip-flops made of 2N1754 Germanium PNP transistors.

The 6R1A differs sightly from the 6R1. One difference is the how the 0% zone is determined. In the 6R1, the 0% zone is always the leftmost major division of the trace. The 6R1A allows the 0% zone to be set arbitrarily.

When a 6R1 is used in a 567 with a 3T77, the horizontal sweep signal is generated by the staircase generator circuit in the 3T77 and from R184 in the staircase generator, the sweep signal is sent to the horizontal amplifier circuit of the 3T77, where it enters the sweep mode switch. Assuming that the sweep mode switch is in the NORMAL or SINGLE DISPLAY positions, the sweep signal is sent out through R318 to pin 20 on P22, the connector on the rear of the 3T77. The 567 carries the signal to pin 8 on P32 of the 6R1. Within the 6R1, the sweep signal is carried to pin 7 of the 0% zone card. On the 0% zone card, the sweep signal is buffered by V43, a Nuvistor cathode-follower, and the buffered sweep signal is sent out from pin 10 of the 0% zone card. On the 0% zone card, the sweep voltage is compared with a fixed voltage, putting D43, a 2mA tunnel diode, into the high voltage state whenever the sweep signal is above about 5 V. The sweep signal goes from 0 V to 50 V for a complete sweep, so 5V corresponds to point 1 major division from the left edge of the display.

6R1 Schematics