Tube warm up time technical measurements

Discussion in 'Portable and Other Gear Measurements' started by atomicbob, Jan 27, 2017.

  1. atomicbob

    atomicbob Friend

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    This thread will be a place for tube warm up thermal measurements.

    I use the following instruments for temperature measurements:
    1. FLIR E4
    2. Fluke 62 Maxx
    3. K-type bead thermocouple with Fluke 80TK and Fluke 189 DMM

    I will add to this collection as I gather more data.

    BH Crack 6AS7 - 12AU7 tube warmup time - PSI plot version.png


    Vali2 6cg7.png


    Saga OTK 6H8C warm up time.png


    EC ZDSE  6C33B-C  6SL7  6D22S warm up time.png
    Svetlana 6D22S Sophia Electric 6SL7
     
    Last edited: Jan 29, 2017
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  2. atomicbob

    atomicbob Friend

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    reserved for additional data.
     
  3. Cspirou

    Cspirou Friend

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    Looks like a minimum of 10min. 30 min would be ideal. At least with the Saga you can use the passive mode while warming up.

    Have you ever tried doing a basic measurement cold vs warm? Like an FR curve or square wave?
     
  4. Priidik

    Priidik Friend

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    From which region of tube are the data collected? Are the results summed somehow or did you end up only showing tc results?
    It's quite unreliable to measure shiny glass with ir so far as I have tried.
     
    Last edited: Jan 28, 2017
  5. atomicbob

    atomicbob Friend

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    I look for the highest temperature on or between the plates of the tube. With the FLIR it is unmistakable from where the highest temperature emanates. Using an IR thermometer such as the Fluke 62 Maxx requires care in aiming, often scanning around the area of interest to obtain the highest temp. Here is an image to help visualize. This is from the Bottlehead Crack and centered on the 6AS7G tube plate.

    FLIR0002.jpg
     
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  6. atomicbob

    atomicbob Friend

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    On the list of experiments for a rainy day.
     
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  7. HitmanFluffy

    HitmanFluffy I like free handies! - Friend

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    Got any of the larger power tube amps to test (2A3, 300B, etc.)?
     
  8. Marvey

    Marvey Loves sex and records

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    Whether tube amps sound better after five minutes or two hours, theres nothing wrong with using tube amps 20-60 seconds after turn on.

    No need to burn incense, make an offering to the gods, memorize spells, recite mantas until tubes reach optimal temperature.
     
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  9. atomicbob

    atomicbob Friend

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    Not at this time. Only big tube amp (well big for me) is the ZDSE. I'll put that one up when measured.

    I would add that for recreational listening a minute is more than adequate. I would prefer to wait a longer, more appropriate time before rendering any judgement on the sound quaility of either the amp or tubes in question.

    My own ritual involves turning on the amp, fixing a beverage, sit and enjoy. This gives the tube 2 ~ 5 minutes of warm-up. Usually have the lab cat join me for the listening session. He prefers old school jazz.
     
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  10. JimL

    JimL Rando

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    Let's remember how tubes work - by thermionic emission. This means that the heater "boils" electrons off the cathode by heating it to operating temperature. In the case of DHT the heater and cathode are one and the same. That process is temperature dependent, but once the cathode has reached operating temperature, the electrical characteristics of the tube should be stable and independent of the temperature of the grid(s) or plate. So, really, the the major temp dependent process is the heating of the cathode, which should occur relatively quickly as its thermal mass is small. The plate heating occurs due to radiant heating from the cathode plus absorbing the energy of the electrons hitting it, but that should not affect the characteristics of the tube since those are primarily dependent on the voltage on the tube and the number of electrons "boiling" off the cathode. So measuring the heating of the plate does not really indicate the temperature dependence of the tube's operation.

    Now, contrast this with transistors, where the characteristics of the transistor or IC chip are also temperature dependent. In the case of a power transistor attached to a heat sink, the characteristics will vary until the entire structure reaches operating temperature. For example, in my SRX Plus amp the output voltage drifts about 50 volts from turn-on and stabilizes in about 30 minutes, due to the MOSFET current sources warming up.

    And in fact, the heat sinks reaching operating temperature is only a rough indication of the characteristics of the chip, since transient increases or decreases in current and voltage passing through the chip can cause localized increases or decreases in heating, which can temporarily alter its temperature, and hence operating characteristics, while minimally affecting the average temperature as reflected by the heatsink. In fact some have argued that solid state devices have a "thermal memory" so that its characteristics will vary depending on what has recently passed through it and this can cause a "memory distortion".
     
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