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Al-1500 blower question

Discussion in 'Amateur Radio Amplifiers' started by KN4CTD, Jan 20, 2019.

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  1. KN4CTD

    KN4CTD Ham Member QRZ Page

    I’m not sure what it’s seeing either. When using the laser function, I have pointed that red dot everywhere on that copper cooler. Even down inside the center of the cooler where it bolts to the tube doesn’t show any higher. I would think that possibly this may be the hottest part due to the closeness to the actual anode and the lack of airflow right there. I get the same results, maybe a tad higher, not using that laser dot function. This does seem to change with distance toward or away from the tube slightly. I’m only gonna get so close to that 3600vdc plate voltage with anything though. I’m guessing the temp gun just isn’t accurate enough for this job.
     
  2. KD2ACO

    KD2ACO Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    It may have a large target (not pin point focus) and the integration is making the measurement read low.

    I use an IR camera attachment on my phone for this kind of stuff but haven’t had to measure tube finals in operation.
     
    Last edited: Jan 22, 2019
  3. N6UH

    N6UH Ham Member QRZ Page

    I guess you're doing this with the covers off? There's probably too much dispersal through the cover. The best way to get the max reading is to move the sensor aperture around until you get the max reading. Some thermometers have a peak hold function as well. The sensor in the Hoo Chung Chong Amazon one I have is below the laser sight and the capture area isn't as parallel to the laser sight as the specs claim it is.
     
  4. KN4CTD

    KN4CTD Ham Member QRZ Page

    I do have the cover off. What do you mean by too much dispersal through the cover? Not much information regarding this thermometer online It’s just another cheap Chinese import that says “tool shed” on it.
     
  5. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I don't trust the 60C reading, that's not very hot at all.

    Try the boiling water test, it's pretty easy. The tube anode should be much hotter than boiling water under normal operation when it's generating power.
     
  6. N6UH

    N6UH Ham Member QRZ Page

    If you have the cover on which you don't some air gets dispersed around the insides of the cabinet, cooler air gets mixed with the main flow etc.
    For the IR thermometer I have the measuring patch is about 2cm (about 3/4 inch) below where the laser is illuminating. Also the optimum distance is about 14 inches away from the target. The size of the target patch read by the sensor also alters in size with range. I guess they're all similar. Try a few experiments with it to make sure you are reading the right area.
     
  7. KN4CTD

    KN4CTD Ham Member QRZ Page

    Just tried boiling water. Opened the microwave door right as it started boiling over. Temperature shows 211 Fahrenheit
     
  8. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Well, that's about right.

    I don't see how the tube could be generating serious power at 60C anode temp, though.

    Sounds like a reflection problem. At 60C, if you could turn off the B+ and have it instantly discharge to zero, you could hold your hand on the tube anode and it wouldn't burn you.

    (Don't try that.:p)
     
  9. KN4CTD

    KN4CTD Ham Member QRZ Page

    Should I try it with the cover on? This thing seems to read half way accurate except on that tube. I’ll try it one more time and see what it reads. I’m not real keen on using it with the cover off anyways!
     
  10. KD2ACO

    KD2ACO Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    The copper could be just the wrong color or reflectivity... throwing the sensor off.

    I wouldn't try putting a thermocouple on an anode at 3kv...

    If you really need to know the temp, maybe it's time to try Ye Olde Fashioned heat indicating paint. These guys may have something.

    https://markal.com/pages/tempil/tempilaq-indicating-liquids
     

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