How hot is too hot?

Discussion in 'Solid State' started by olddude55, Aug 8, 2018.

  1. olddude55

    olddude55 AK Subscriber Subscriber

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    Bought a Hafler DH-200 last week, seller said he had been using it regularly until about a week before he put it up for sale.
    In my system, sounded sweet but got hot driving Maggies. Not egg-frying hot, not hot enough to burn my hand, but hot.
    Whereas, when driving just headphones (Stax with the SRD-7SB box) it was only warm.

    Normal? Again, the unit sounded terrific.
     

     

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  2. Watthour

    Watthour Electron Rancher - JS3600

    Quantified temperature would be helpful. Typically 130°F (55°C) is too hot to keep a finger on for more than 5 seconds without discomfort. That is well below the temperature limits of most components, however. Personally, at 55°C and over I would be looking for a way to improve the heat sinks or force more heat dissipation somehow.
     
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  3. olddude55

    olddude55 AK Subscriber Subscriber

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    D'oh! Never thought of just using a thermometer...
    I could hold my hand on the amp for as long as I wanted without burning. Also, I use an open rack, no back or sides, and there's about 5 inches between the top of the amp and the bottom of the next shelf. Plenty of airflow in an air-conditioned house.
    I'm taking the old Hafler to a tech guy today just to have it checked out. Like I said, sounded really sweet when I had it in the system for a couple of days.
     
  4. icenine

    icenine Super Member

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    I just started using a Hafler P230 and it is very hot to the touch after about 20 minutes, even when driving Klipsch RB-5s.
    It is hot all over. However I don't hear any distortion and it has new output fuses. I left it on for like 2 hours in with the preamp off and it was still super hot. I can lay my fingers on it but it is uncomfortable.

    It is well ventilated but we are also having a heat wave in SoCal so the room is probably 90+ degrees. Last night I used it for about an hour then switched over to a tube amp lol.

    Will these catch on fire or will internal fuses shut it down before hand?
     
  5. invaderzim

    invaderzim AK Subscriber Subscriber

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  6. techguy0192

    techguy0192 AK Subscriber Subscriber

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    Wow.....I can't imagine listening to music in a 90* room as being enjoyable.
     
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  7. icenine

    icenine Super Member

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    MY AC is dead.
     
  8. olddude55

    olddude55 AK Subscriber Subscriber

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    I've done it. Hope I never have to do it again though.
     
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  9. Superampman

    Superampman AK Member Subscriber

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    150F is borderline max for an AB amp even being pushed hard for an extended period.
     
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  10. Roadrash

    Roadrash AK Subscriber Subscriber

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    Thanks for the link. I'm going to order one of those for my Citation 22.
     
  11. slimecity

    slimecity Super Member

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    You can get laser handheld thermometers now for peanuts and that will give you an objective measurement.

    There are rules of thumb for acceptable temperatures for healthy AB amplifiers and also Class A amps, which tend to run hotter.

    Output devices usually have a max temperature rating, and the size of the heatsink is calculated to achieve the proper thermal heat dissipation. If something is wrong then yes, you will need to try to find the cause. Generally if there is an problem then one channel will run hotter than the other - as an indicator that something is actually wrong.
     
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  12. elnaldo

    elnaldo Addicted Member

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    Thermal circuit breakers I've seen mounted on heat sinks (class AB amps) were 90 and 75°C.
     
  13. icenine

    icenine Super Member

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    My DC offset on my Hafler P230 is about 2.5mv DC on both left and right channels with speakers disconnected and preamp volume at zero.
    With volume knob halfwayup it fluctuates between 2.5mv-4.0mv DC on left channel and 1.9-2.5mv DC on right channel.

    I guess its safe to crank. Just very hot!
     
  14. DavidF

    DavidF Active Member

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    That does not sound unusual though the bias current may be set a bit high. I don't recall if there is bias adjustment on the stock boards. I have a modified DH200 with different circuit boards and have the bias set on the high side. The heat sinks run quite warm and you could hold your hand on them, but it would get uncomfortable after a while. Setting the bias down allows for cooler operation but it still gets cozy-warm. I actually do not use this amp in the hot summer months just because it is a bit of room heater.
     
  15. nj pheonix

    nj pheonix AK Subscriber Subscriber

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    It doesn't do people a hell of a lot of good either.
     
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  16. olddude55

    olddude55 AK Subscriber Subscriber

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    Well, it was too hot after all. Tech guy called yesterday, right channel bias pot needs replaced. He's going to replace both pots and recap the amp. Should have it back next Wednesday.
     

     

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  17. bowtie427ss

    bowtie427ss arigato gozaimashita Subscriber

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    Maggies pull a lot more current from your amplifier than the Stax energizer.

    Sounds like you are within normal operating range.
     
  18. olddude55

    olddude55 AK Subscriber Subscriber

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    The right channel is getting hotter than the left. I could feel that before I took it in. The heat sinks felt the same but the top of the amp was hotter on the right side.
    Those Maggies will get the Emotiva kind of warm, too.
    At any rate, can't wait to get the old Hafler back. Got a DH-101 to pair it with, but I'm going to recap the 101 myself.
     
  19. scoloheros

    scoloheros Well-Known Member

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    If you want to go cheap, a laptop cooling pad works, I found one for $4 at a thrift store. Make sure it has the plug you want, some are standard outlet and some have a USB plug, I think. The one I found has the standard plug, I plug it into the back of a unit that gets hot. Place it on top over the vents.
     
  20. olddude55

    olddude55 AK Subscriber Subscriber

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    According to the tech, it should get hot driving Maggies. Not second-degree burn hot, but hot. I used to use a Stereo 70 and that little mother got hot enough to burn flesh. The Hafler doesn't get anywhere near that hot, even with the non-functioning bias pot.
     

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