Delay relay: Difference between revisions
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Several later tube-era Tektronix oscilloscopes such as the [[549]], [[581]] and [[585]] that already use semiconductor rectifiers for the anode voltages contain 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 | [[File:Amperite delay relays 1953.pdf|thumb|300px|right|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 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. | |||
The part | |||
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Revision as of 03:16, 24 July 2021
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.