Delay relay: Difference between revisions
m (→535) |
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|148-0002-00 | |148-0002-00 | ||
|6NO45 | |6NO45 | ||
|[[545]],[[585]],[[555]] | |[[535]],[[545]],[[585]],[[555]] | ||
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|148-0006-00 | |148-0006-00 |
Revision as of 10:03, 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. (The original literature used NO and N0 prefixes interchangeably.)
Part # reference | ||
---|---|---|
Tek Part | MFR Part | Used in |
148-0002-00 | 6NO45 | 535,545,585,555 |
148-0006-00 | 26NO45T | ? |
148-0009-00 | 6NO15T | ? |
148-0021-00 | 6NO30T | 547 |
148-0023-00 | 18NO30 | 585A |