502

The Tektronix 502 is a dual-beam oscilloscope introduced in 1958, followed by the 502A in 1963. There is also a rack-mount model, the RM502A.

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1 MHz dual beam differential scope Tek 502 front (with Single Sweep Mod 104) Produced from 1958 to 1973 Manuals 502 (early) Instruction (OCR PDF, 15M) 502 (late) Instruction (OCR PDF, 26M) 502A Instruction (OCR PDF, 8M) Tektronix 502A sn 31,000-up Factory Calibration Procedure, June 1969 (PDF, needs OCR) (All manuals in PDF format unless noted otherwise)

Manuals – Specifications – Links – Pictures

Both beams have differential inputs. The horizontal deflection plates are common to both beams.

Mod 104 on a 502 provides single sweep lockout. This feature is standard on the 502A, which also has beam finder switches for each channel.

A recessed switch in the left side panel allows the upper beam amplifier to be connected to the horizontal deflection plates for single-beam X-Y operation, providing a differential X input with the same sensitivity as the Y channel. The upper beam is positioned off screen in this mode.

Key Specifications

Deflection	100 μV/cm to 20 V/cm, 1−2−5, ±3%
Bandwidth	1 MHz @ 200 mV/cm and above; 400 kHz @ 50 mV/cm, 200 kHz @ 5 mV/cm, 100 kHz @ 200 μV/cm
CMRR	502A: 40,000:1 @ 100 mV/cm and 1 kHz
Input impedance	1 MΩ // 47 pF
Sweep	1 μs/cm to 5 s/cm, 1−2−5, ±3%; magnifier ×2, ×5, ×10 or ×20
CRT	Early 502: Type T60P2/T502P2/T5020P2; Late 502, 502A: Type T5021P2; (P1, P7 or P11 were available as options) 10 vertical and 10 horizontal 1 cm divisions 3 kV acceleration
Dimensions	597 mm (23½") × 286 mm (11¼") × 381 mm (15") L×W×H
Weight	23.6 kg (52lb)

Prices

Year	1959	1961	1963 (A)	1971 (A)
Catalog price	$825	$825	$1,050	$1,265
2018 value	$7,070	$6,890	$8,560	$7,790

Internals

There is a transistor-regulated 6.2 V_DC heater supply for the tubes in the first stage differential amplifier. This heater supply uses the −150 V supply as its reference. The −150 V supply uses a 5651 voltage reference tube as its reference. There is no post-deflection acceleration. The CRT cathode voltage is −2.9 kV.

Later 502A have solid state (plus nuvistor) input stage, a 6DJ8 as the deflection amplifier, and transistors as amplifiers and emitter followers (only in the newest version).

The early 502 uses a single supply for the upper beam and lower beam CRT cathodes (HV transformer 120-114). Later models (1959+, see 070-090) and the 502A have separate supplies for the two CRT cathodes (HV transformer 120-150). This improvement allows slight differences in horizontal CRT sensitivity between the two beams to be cancelled out in step 8 of the calibration procedure.

Links

Tektronix 502A @ amplifier.cd (many internal pictures)

Pictures

502

502 without Mod 104, front
502 with Mod 104 (single sweep), front
502 front view
502 left
502 right
rubber shock mount of amplifier sub-chassis
502 bottom
502 trace
502 trace

502A

502A
502A right internal
502A right
502A left
502A rear
Solid-state input stage with two 6DJ*
502A vertical amp sn 25,997 to 30,999

RM502A

RM502A
RM502A rear
RM 502A
RM 502A display
RM 502A bottom
RM 502A transformer wiring
RM 502A top
RM 502A vibration-isolated vertical amp

Third version 502A, serial number ≥31,000

top side lower beam input amp and attenuator, bottom side of upper beam vert input board
late model RM502A
late model RM502A
late model RM502A
late model RM502A
late model RM502A
late model RM502A
late model RM502A

Diagrams

502A block diagram
502A vertical amplifier
Early 502 CRT circuit, 120-114 transformer (secondary transformer pin numbers incorrect)
Later 502 CRT circuit, 120-150 transformer
502A CRT circuit, 120-150 transformer
Cartoon in schematic: Mountain Climber