Delay relay: Difference between revisions

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Tube_18NO30.jpeg |  18NO30 (from [[585A]])
Tube_18NO30.jpeg |  18NO30 (from [[585A]])
Delay relay.png | Delay relay circuit from [[581]]/[[585]]. K600 is the delay relay, K601 the main anode voltage relay.
Delay relay.png | Delay relay circuit from [[581]]/[[585]]. K600 is the delay relay, K601 the main anode voltage relay.
Amperite delay relays 1953.pdf | Data from Radio's Master, 18th Ed., 1953
Amperite delay relays 1957.pdf | Data from REPCO Radio Electronic Master Official Parts and Equipment Catalog, 21st Ed., 1957
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[[Category:Relays]]
[[Category:Relays]]

Revision as of 03:39, 24 July 2021

Amperite Delay Relays, 1953 (click to enlarge)

Several later tube-era Tektronix oscilloscopes such as the 549, 581 and 585 that already use semiconductor rectifiers for the anode voltages contain a thermal delay relay such as the 6N045T or 6N030T in a circuit that delays turn-on of the main supply voltages until the tubes are warmed up. This is normally not needed in scopes with tube rectifiers because of their inherent slow-start behavior.

When the scope is turned on, a bi-metal strip in the delay relay is beginning to heat up. After the delay time (30 to 60 seconds depending on the instrument), the bi-metal strip closes a contact that energizes the main relay, thereby turning the anode voltages on. One of the main relay's contacts is used to make it self-holding, while at the same time cutting out the delay relay. At this time, the bi-metal strip is beginning to cool so it will be ready to provide delaying turn-on again in the event of a power outage.

The part number is decoded as: 6 − Heater Voltage, NO − Normally Open / C − Normally Closed, XX − delay time, T − B9A (Noval) miniature 9-pin base / no suffix − octal base). For example, a 6NO30T is a 6 Volt filament/heating element with a normally open contact and a delay time of 30 seconds, with a miniature 9-pin base.

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