420
The Tektronix 420 is a high-voltage power supply used in the Type 507 and Type 517 scope. It contains the transformers, rectifier tubes and filter capacitors in a separate enclosure with ceramic output feed-through posts.
Key Specifications
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Output voltages are +20 kV and –4 kV. Later models add +13.3 kV and +6.6 kV output taps.
Internals
The 420 contains two transformers, one for the high voltage, and a second for the HV rectifier heaters. The HV rectifiers are five 1X2 tubes, one for the negative and four in a Cockroft-Walton multiplier for the positive outputs.
The transformers are driven by independent oscillators using tubes located on the mainframe chassis, a 6AU5 for HV and a 6AQ5 for heaters. In the 517, the HV oscillator runs off an unregulated supply through its own DC series regulator with no feedback path from the HV side, only the oscillator input voltage is regulated. The 507 HV oscillator, supplied from the regulated +225 V rail, takes feedback from the negative HV output..
Pictures
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Entry in 1950 Catalog
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Schematic of 420 in the Type 517
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later model 420 (with 13 and 6 kV outputs) in a 517
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opening power supply type 420A, five 1X2 high voltage rectifier tubes
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opening power supply type 420A, many capacitors
Some Parts Used in the 420
| Part | Part Number(s) | Class | Description | Used in |
|---|---|---|---|---|
| 1X2 | 154-0005-00 | Vacuum Tube (Diode) | high-voltage rectifier | 420 • 507 • 565 |