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Several tube-era Tektronix oscilloscopes such as the [[549]], [[581]] and [[585]] contain a circuit that delays turn-on of the main supply voltages until the tubes are warmed up. | [[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. | |||
[[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. | |||
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 instrument), the bi-metal strip closes a contact that energizes the main relay. One of the main relay's contacts is used to make it self-holding while at the same time cutting out the delay relay, | 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. | |||
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 original literature used NO and N0 prefixes interchangeably.) | |||
{| class="wikitable" | |||
|- | |||
! colspan="3" | Part # reference | |||
|- style="text-align:center;" | |||
| Tek Part | |||
| MFR Part | |||
| Used in | |||
|- style="text-align:center;" | |||
|148-0002-00 | |||
|6NO45 | |||
|[[535]],[[545]],[[585]],[[555]] | |||
|- | |||
|148-0006-00 | |||
|26NO45T | |||
|? | |||
|- | |||
|148-0009-00 | |||
|6NO15T | |||
|? | |||
|- | |||
|148-0021-00 | |||
|6NO30T | |||
|[[547]],[[549]] | |||
|- | |||
|148-0023-00 | |||
|18NO30 | |||
|[[585A]] | |||
|} | |||
==Links== | |||
* Rajesh's time delay relay video: [https://youtu.be/ma1GSj9XWtM Part 1] / [https://youtu.be/2m3uEKUIWiA Part 2] | |||
==Reference== | |||
* [https://ia804505.us.archive.org/13/items/tek_1977_parts_price_list_number_35a/tek_1977_parts_price_list_number_35a.pdf Tektronix Parts Price List Number 35a (1977) - Page 6.053] | |||
==Pictures== | |||
<gallery> | <gallery> | ||
6N045 1.jpg | | 6N045 1.jpg | 6NO45 delay relay (from [[585]]) | ||
6N045 2.jpg | | 6N045 2.jpg | 6NO45 | ||
6N045 3.jpg | | 6N045 3.jpg | 6NO45 | ||
6N045 4.jpg | | 6N045 4.jpg | 6NO45 | ||
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 | |||
</gallery> | </gallery> | ||
[[Category: | [[Category:Relays]] |