STF-8300M -20deg setting @35deg ambient ramps up 100% cooler power within short time

Discussion in 'STF Series CCD Cameras' started by astrodwp, Mar 21, 2019.

  1. astrodwp

    astrodwp Cyanogen Customer

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    SFT-8300M; ambient Temperature at 35deg with 60% humidity......Set cooler at -20deg....sensor reached -20deg in normal time using about 50% cooler power. but in less than 40 minutes the cooler was at 100% and not holding temp.
    i also tried ramping up from -5 deg, -10 deg, -15deg and -20deg every 10 minutes....same result.
    I also have an ST-8300c camera and tried same experiment and it reached -20deg with 30% cooler power and held all night.
    Any ideas as to what is wrong?
    also telescope is at remote site....any way to do trouble shooting?
    thanks
    dave
     
    astrodwp, Mar 21, 2019
    #1
  2. Doug

    Doug Staff Member

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    Usually not maintaining delta is indicative of a weak fan.

    That said, a 55 degree delta is more than expected for a single stage cooler.

    Can you provide serial numbers for both cmaeras?
     
    Doug, Mar 21, 2019
    #2
  3. astrodwp

    astrodwp Cyanogen Customer

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    don't have serial number handy.....is the SN on outside of camera? if so can probably get them in a couple of days.....snow storm going on now.
    If it is not something simple....like some foreign object causing fan to lose RPM....can the fan be replaced in the field or does it need to be replaced at the repair shop.
    both camera are out of warranty.
    dave
     
    astrodwp, Mar 21, 2019
    #3
  4. astrodwp

    astrodwp Cyanogen Customer

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    probably should of added that i am using maxim DL for cooler control.....and i thought maxim DL cooler set point waa a delta? so the delta, i thought, would be 20 deg?
     
    astrodwp, Mar 21, 2019
    #4
  5. Doug

    Doug Staff Member

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    No, MaxIm DL temperature setpoint is absolute. It has to be, because otherwise calibration files would not work properly.
     
    Doug, Mar 21, 2019
    #5
  6. astrodwp

    astrodwp Cyanogen Customer

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    Reply:.........................................

    STF-8300M SN: 83F010777
    ST-8300C SN: 831001179

    Also some clarification: ambient temp was 35deg F or (+1.7 deg C).....cooler set point was -20deg C. (delta of 21.7 deg C)
    1) Set cooler set point at -20deg C, started at about 50% power and next time i looked about an hour later cooler power was at 100%
    2) Ramped down cooler temp starting at -5 deg C, -10deg C, -15deg C and -20deg C every 10 minutes.

    -5 deg C first reached -5 deg C at about 55% cooler power
    29% at 5m
    25% at 10m
    -10 deg C first reached -10 deg C at 38% cooler power at 1 min
    38% at 5m
    35-39% at 10m
    -15 deg C first reached -15 deg C at 50% cooler power at 1.5 min
    48-53% at 5m
    50-55% at 10m
    -20 deg C first reached -20 deg C at 71% cooler power at 1.5 min
    76-79% at 5 min
    92-94% at 10 min
    100% at 11 min

    second test with ST-8300C
    ramped temp directly to -20deg C.....Held -20deg C temp all night at about 30% cooler power

    dave
     
    astrodwp, Mar 23, 2019
    #6
  7. Bill

    Bill SBIG Service and Repairs Staff Member

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    Dave,

    I think this camera should be sent in for evaluation. Send me an email, bill@sbig.com, and I'll give you the details for doing so.

    -Bill
     
    Bill, Mar 25, 2019
    #7

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