Tube warm up time technical measurements

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

  1. atomicbob

    atomicbob dScope Yoda

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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

    (added 20180116)
    4. Keysight E2308A thermistor temperature probe
    5. Omega OS136-1-MV infrared sensor D:S=6:1 field of view
    6. Picotech Picoscope 2205A with PicoLog Recorder SW for data logging

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

    Continuous IR temperature measurement logging system:
    (added 20160116)
    DSC_0005a.jpg

    The following five temperature measurements were made manually with the FLIR and Fluke instruments:
    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


    20171218 ZDT Jr tube warm up time deg F.png

    The following measurements were made using the system shown in the picture above:
    (added 20180116)
    20180111_BH_Crack_6080_temp_warmup.png
    During the measurement period a fan turned on to redistribute heat through the room. Bet everyone can find both fan on and fan off times.

    20180109_BH_Crack_6080_temp_cooling1.png
    A continuous data logging system is conducive to measuring all sorts of changes.

     
    Last edited: Jan 16, 2018
  2. atomicbob

    atomicbob dScope Yoda

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    reserved for additional data.
     
  3. Cspirou

    Cspirou They call me Sparky

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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 dScope Yoda

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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 dScope Yoda

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

    HitmanFluffy Hoping to see real genitals someday! - Friend

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    Got any of the larger power tube amps to test (2A3, 300B, etc.)?
     
  8. purr1n

    purr1n Finding his inner redneck

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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.
     
  9. atomicbob

    atomicbob dScope Yoda

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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 Tongues KG's hairy starfish for fun

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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".
     
  11. atomicbob

    atomicbob dScope Yoda

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    @Cspirou discussion about a RaspPi temperature data logger in the Modi MB for the masses thread inspired me to create the system shown in the picture added to post 1 and repeated again here:

    DSC_0005a.jpg

    I had a Picotech Picoscope 2205A sitting on the shelf in the lab, not getting much use since the Picoscope 5243b arrived. Turns out Picotech has a data logging application for the 2205A. With an OS136-1-MV sensor from Omega, custom cable and an iFi 15V power supply the above continuous non-contact IR temperature logging system was born. A couple of measurements using this system have been added to post 1 above. This is superior to manual measurements in several ways. No more babysitting the measurements. Time of measurement interval precision is improved. Higher resolution of measurement intervals are easy to perform given the automation.
     
    Last edited: Jan 17, 2018
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  12. zhouharvey

    zhouharvey PayPal’s $2 Sensible Enforcer

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    30 minutes is too long to wait!
     
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  13. zhouharvey

    zhouharvey PayPal’s $2 Sensible Enforcer

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    Whoever loves to wait 30 minutes to warm up some tubes, is real XXX!
     
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  14. Hands

    Hands Overzealous Auto Flusher - Measurbator

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    I put tubes up my ass before listening to expedite the warm up process. Win-win for sonic perfection and personal stimulation.
     
  15. Elnrik

    Elnrik Super Friendly

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    I guess Hands is really into anal-log sound reproduction.
     
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  16. maverickronin

    maverickronin Friend

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    You have to be careful with that to avoid breakage.

    Also, many people with 2A3 or 300B based amps also experience trouble with this technique. Better to start out with something more manageable like an MCTH.
     
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  17. winders

    winders Mentally ill. Do not engage.

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    Nah. Tubes are much smaller than his head so they fit just fine! :bird:
     
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  18. Hands

    Hands Overzealous Auto Flusher - Measurbator

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    Yeah, even the 7 6SN7 tubes from my Super 7 aren't really enough for me.
     
  19. zerodeefex

    zerodeefex Grumpiest admin

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    Forget the pot, this is like the asphalt calling the kettle black.
     
  20. winders

    winders Mentally ill. Do not engage.

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    So I guess the three of us are in the same boat then!
     

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