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Delay relay: Difference between revisions
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[[File:Amperite delay relays 1953.pdf|thumb|300px|right|Amperite Delay Relays, 1953 (click to enlarge)]] | [[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. | 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. | ||
[[Bruce Baur]] said: | |||
<blockquote> | |||
The reason Tek resorted to time delay on the B+ is that the high current tubes, like the series regulators, did not like to produce current with a cold to warm cathode. | |||
Until the cathode reached its normal hot running temperature there was a tendency for it to strip cathode material off of the cathode and shorten the life of the tube. | |||
The [[5U4]] filament warms up fast, but the [[6X4]] warms up about the same as the other tubes and acts as a time delay for the reference that the supplies need to operate from the 5U4. | |||
</blockquote> | |||
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. | 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. | ||