485: Difference between revisions
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The '''Tektronix 485''' is a dual-trace, portable analog oscilloscope with a maximum | The '''Tektronix 485''' is a dual-trace, portable analog oscilloscope with a maximum | ||
bandwidth of 350 MHz. | bandwidth of 350 MHz, [[introduced in 1972|introduced in March of 1972]]. | ||
The project leader for the horizontal section of the 485 was [[Murlan Kaufman]]. | |||
The impedance of the inputs can be set individually to 50 Ω or 1 MΩ. | |||
The scope achieves its maximum bandwidth when the inputs are in 50 Ω mode. | The scope achieves its maximum bandwidth when the inputs are in 50 Ω mode. | ||
A distinguishing feature – at least in a portable oscilloscope of its period – is the Alternate Horizontal Mode. | A distinguishing feature – at least in a portable oscilloscope of its period – is the Alternate Horizontal Mode. | ||
In this mode, the B timebase is shown in a separate full-width scan, as opposed to the more common Mixed Mode, | In this mode, the B timebase is shown in a separate full-width scan, as opposed to the more common Mixed Mode, | ||
where the B timebase is shown on the same line as the A timebase, after the delay time | where the B timebase is shown on the same line as the A timebase, after the delay time. | ||
The [[465]], which was introduced after the 485, only received this feature in its "B" incarnation (465B). | The [[465]], which was introduced after the 485, only received this feature in its "B" incarnation (465B). | ||
485-1 | Variant 485-1 omits the "A EXT Trigger display", as does variant 485-2 which additionally only has 50 Ω inputs. | ||
{{BeginSpecs}} | {{BeginSpecs}} | ||
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* [http://www.amplifier.cd/Test_Equipment/Tektronix/Tektronix_other/485.html Tek 485 @ amplifier.cd] | * [http://www.amplifier.cd/Test_Equipment/Tektronix/Tektronix_other/485.html Tek 485 @ amplifier.cd] | ||
* [https://youtube.com/watch?v=7Qg6ory3L8Y 485 troubleshooting] @ YouTube | * [https://youtube.com/watch?v=7Qg6ory3L8Y 485 troubleshooting] @ YouTube | ||
==Internals== | |||
The 485 includes a switching power supply and uses [[155-0078-00|custom integrated circuits]] for most of the gain blocks. Triggering uses [[tunnel diodes]]. | |||
==Maintenance issues== | ==Maintenance issues== | ||
Revision as of 05:14, 14 October 2021
The Tektronix 485 is a dual-trace, portable analog oscilloscope with a maximum bandwidth of 350 MHz, introduced in March of 1972. The project leader for the horizontal section of the 485 was Murlan Kaufman.
The impedance of the inputs can be set individually to 50 Ω or 1 MΩ. The scope achieves its maximum bandwidth when the inputs are in 50 Ω mode.
A distinguishing feature – at least in a portable oscilloscope of its period – is the Alternate Horizontal Mode. In this mode, the B timebase is shown in a separate full-width scan, as opposed to the more common Mixed Mode, where the B timebase is shown on the same line as the A timebase, after the delay time.
The 465, which was introduced after the 485, only received this feature in its "B" incarnation (465B).
Variant 485-1 omits the "A EXT Trigger display", as does variant 485-2 which additionally only has 50 Ω inputs.
Key Specifications
| Input Impedance | 50 Ω / 1 MΩ // 20 pF |
|---|---|
| Rise time | 1 ns (50 Ω) / 1.4 ns (1 MΩ) |
| Bandwidth | 350 MHz (50 Ω) / 250 MHz (1 MΩ) |
| Deflection | 5 mV/div to 5 V/div in 1−2−5 sequence, 2% accuracy |
| Time Base | 1 ns/div to 0.5 s/div in 1−2−5 sequence |
| CRT | 154-0652-00 and 154-0652-05, 21 kV acceleration, 8x10 divisions (0.8cm/div) |
| Weight | 21.5 lb/9.3 kg |
| Power | AC 90-136V/180-272V 48-440Hz, 60W @115V |
Links
- Tek 485 @ amplifier.cd
- 485 troubleshooting @ YouTube
Internals
The 485 includes a switching power supply and uses custom integrated circuits for most of the gain blocks. Triggering uses tunnel diodes.
Maintenance issues
A healthy Tek 485 CRT has been observed to have a filament current of 98 mA. A broken Tek 485 CRT that lost its vacuum was observed to have a filament current of 153 mA.
Pictures
External
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Time base A, External trigger display switch
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Internals
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Top, Horizontal Amp board
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Underside, Power supply, A-Trig board
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LHS, Vertical Amp board
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RHS, Sweep/Inverter board
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A-Trigger board
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Vertical attenuator Assy
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Vertical attenuator Assy, 50Ω Board
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Vertical attenuator Assy, Hi-Z Board
