502

Manuals – Specifications – Links – Pictures

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.

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.

If the combination of time base setting and magnification selector results in a sweep faster than 1 μs/div, the horizontal scale is not calibrated, and a lamp on the front panel lights up to remind the operator of that.

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
2021 value	$7,740	$7,530	$9,370	$8,530

Internals

The −150 V supply uses a 5651 voltage reference tube as its reference.

The 6.2 V_DC heater supply for the tubes in the first stage differential amplifier is transistor-regulated. This heater supply uses the −150 V supply as its reference.

There is no post-deflection acceleration. The CRT cathode voltage is −2.9 kV.

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.

Later 502A models have a 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 502 has a 123 °F (50.5 °C) thermal cutoff switch.

Links

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

• Tektronix 502A internals @ youtube (German)

Pictures

502

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  502 with (single-beam) X-Y display

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  502 Mod.104 (single sweep), front

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  502 Mod.104 (single sweep), front from lower left

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  502 left interior

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  502 right interior

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  rubber shock mount of amplifier sub-chassis

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  502 bottom

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  502 trace

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  502 trace

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  502 front panel without knobs

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  502 power supply section in operation

502A

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  502A

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  502A right internal

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  502A right

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  502A left

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  502A rear

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  Solid-state input stage with two 6DJ*

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  502A vertical amp sn 25,997 to 30,999

RM502A

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  RM502A

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  RM502A rear

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  RM 502A

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  RM 502A display

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  RM 502A bottom

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  RM 502A transformer wiring

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  RM 502A top

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  RM 502A vibration-isolated vertical amp

Third version 502A, serial number ≥31,000

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

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  late model RM502A

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  late model RM502A

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  late model RM502A

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  late model RM502A

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  late model RM502A

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  late model RM502A

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  late model RM502A

Diagrams

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  502A block diagram

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  502A vertical amplifier

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  Early 502 CRT circuit, 120-114 transformer (secondary transformer pin numbers incorrect)

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  Later 502 CRT circuit, 120-150 transformer

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  502A CRT circuit, 120-150 transformer

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  Cartoon in schematic: Mountain Climber

Applications

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  Tek 502A in a Physiology lab