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.
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 |
| 2018 value | $7,070 | $6,890 | $8,560 | $7,790 |
Internals
There is a transistor-regulated 6.2 VDC 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.
The 502 has a 123 °F (50.5 °C) thermal cutoff switch.
Links
- Tektronix 502A @ amplifier.cd (many internal pictures)
Pictures
502
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502 without Mod 104, front
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502 with Mod 104 (single sweep), front
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502 front view
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502 left
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502 right
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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
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
