503

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Tektronix 503
450 kHz differential-input scope
Tektronix 503

Produced from 1960 to 1973

Manuals
Manuals – Specifications – Links – Pictures

The Tektronix Type 503 is a low-cost, low-bandwidth monolithic oscilloscope introduced in 1960 specializing in X-Y mode but also containing a sweep circuit. It features differential signal inputs.

There is a similar sister model, the 504, with single-ended inputs. A rack-mount version, the RM503, was also available.

The 503 was $625 in 1960 versus, for example, $1000 for the 516 in 1960.

Due to is its low bandwidth, the 503 can operate at high sensitivities while not responding to interference from broadcast transmitter RF fields, making it suitable for biomedical work.

A large market for the 503 was in electronics labs of educational institutions. The differential inputs are useful for entry level students to experiment with observing voltages not referenced to ground.

Key Specifications

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The 503 features two identical phase matched amplifiers with true differential inputs. The scope has a bandwidth specification of 450 kHz and sensitivity to 1 mV/cm.

The standard version 503 utilized a P2 phosphor CRT that provides a slightly longer trace decay time for ease of photographing the display.

Internals

The 503 is mostly a vacuum tube design with a differential transistor stage following the differential input amplifiers.

The CRT (T5030) does not use post-deflection acceleration, resulting in the CRT cathode operating at -3 kV.

The power supply design is unique in that unlike other scopes where the high frequency transformer only generates the CRT operating voltages, in the 503 it generates all the operating voltages other than the two filament circuits which are supplied by the AC mains power transformer. It is basically a tube-based (secondary) switch-mode power supply (SMPS). A 6DQ6 power pentode, V620, feeds switched primary current to transformer T620. The switching frequency of V620 is between 25 kHz and 30 kHz, enabling T620 to operate efficiently with much lower core mass than would be required for a transformer operating at mains frequency.

Pictures


Some Parts Used in the 503

Page Class Description Used in
5642 Vacuum Tube (Diode) directly-heated high-voltage rectifier 310 310A 316 317 360 453 502 502A 503 504 506 513 515 516 529 RM529 533 533A 535 536 543 543A 543B 545 545A 545B 547 551 555 556 567 575 581 581A 585 585A 647
6AL5 Vacuum Tube (Dual Diode) high-perveance dual diode 163 181 190 310 310A 315 316 317 502 502A 503 511 511A 512 516 517 517A 526 535 535A 545 545A 549 581 581A 585 585A 551 C T Telequipment S52
6BC7 Vacuum Tube (Diode) triple diode 503 504
6BJ7 Vacuum Tube (Diode) triple diode 503 526
6BL8 Vacuum Tube (Triode/Pentode) triode-pentode combo 503 504 516 549 Telequipment D52 Telequipment S31 Telequipment S32 Telequipment S32A Telequipment S51 Telequipment S52
6CB6A Vacuum Tube (Pentode) pentode 105 112 316 317 503 504 513 517 517A 541 535 545 63 2A63
6DJ8 Vacuum Tube (Dual Triode) dual triode 80 132 161 310A 316 317 3A75 502 502A 503 504 515 516 519 526 529 RM529 533 535 536 543 544 545 545A 545B 546 547 549 555 556 565 581 581A 585 585A 661 2A60 63 2A63 3A7 3A8 1121 1A4 67 81 82 86 3B1 3B4 1S1 B O W Z Telequipment S32A Telequipment D52 Telequipment TD51 Telequipment S52 Telequipment S51 Telequipment Type A
6DK6 Vacuum Tube (Pentode) high-frequency miniature pentode 180 503 513 514 541 543 535 545 545A 551 555
6DQ6 Vacuum Tube (Pentode) power pentode 503 504
8393 Vacuum Tube (Triode) Nuvistor triode 453 454 1A6 1A7 503
T5030 CRT CRT 503 504 560 561 661