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Thread: "Acceptable" CPU Temps?

  1. #21
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    Right. Probably the power supply board. There is no heating coming from the inverter board.
    http://cgi.ebay.de/202654235492

    Blew out dust from the power supply board. Will give it another try. Also put a fan right on top of the power supply air inlets. That may help.
    Last edited by PeterNC; May 27th, 2020 at 10:35 AM.

  2. #22
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    Sorry for hijacking the thread. I have requested the moderators split this off.

    With the fan on the power board air inlet the screen flickered and shut down again. Now experimenting with another fan on the inverter air inlet. Also turned the brightness way down (which should put less strain on the inverter).

    So far this seems to work pretty well. Will know more by 5PM when I shut it down for the day.
    Last edited by PeterNC; May 27th, 2020 at 12:27 PM.

  3. #23

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    Back to the original thread. I'm not sure how the older Intel CPUs measured the temperature. They used to do what was called a corner temperature. This was an external sensor at the corner of the die. It is not junction temperature.
    The Junction temperature should not go over 100 degrees C.
    As for Chuck's notes, the silicon grease has low thermal conductivity. The grease evaporates over time, as all silicon oils do.
    His other choices may work better or worse than the recommended stuff. The zinc oxide is a better conductor than the oil.
    As for putting metallic grease, I tend to agree but there are those that use the low temperature metal.
    I don't recommend the indium/gallium metals for any computer you expect to keep for more than 3 years. It does cause pitting of the heat spreader and heatsink. never use it on aluminum. One tiny nick in the oxide coating of the aluminum and it will turn it to junk. For gamers that expect to upgrade in a couple years it is fine. Please don't put that stuff on classic machines.
    As for temperature readings. A corner temperature of 100 degrees C is way too much. I would allow at least 10 or 15 degrees window there. Also, the heat spreader on older Intel processors use ordinary silicon heat sink grease. It ages faster with temperature. Any temperature spec is likely designed for a 5 year half life.
    I see the note that it seems that there was only a small amount of the compound. As long as it was covering the entire surface it was doing fine. That is the way it should be, just enough to cover without big gobs around the edges. You want it to be as thin as possible ( no more than needed ).
    Dwight

  4. #24
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    Quote Originally Posted by PeterNC View Post
    With the fan on the power board air inlet the screen flickered and shut down again. Now experimenting with another fan on the inverter air inlet. Also turned the brightness way down (which should put less strain on the inverter).

    So far this seems to work pretty well. Will know more by 5PM when I shut it down for the day.
    I've repaired quite a few monitors with faults similar to yours. Basically what happens is that the components get so hot that they desolder themselves from the PCB. The solder joints will develop micro cracks which appear under magnification as a double ring on the solder joint that make intermittent connection. No amount of cooling will fix this issue, you'll need to go in and repair those joints. The best method is to remove all of the existing solder on the joint via your preferred method (solder sucker or braid) and then use new solder on the joint. Touching up the existing joints with flux isn't recommended because the solder has been damaged by the heat and becomes brittle, especially the lead free ROHS crap.

    Fortunately, it's usually pretty easy to spot where the fault is because the solder will start turning a golden color from being overheated, and in extreme cases, the PCB itself will turn yellow/brown. You'll also have to look out for bad components, dead power resistors and diodes are the most common after cooked capacitors.

    The power supply board is almost always the culprit, I've not encountered a faulty inverter board in monitors yet. usually the CCFL backlights fail long before the inverter board does, and those are a pain to change. I usually opt to LED mod the LCD panel instead because it uses far less energy and is much brighter.

  5. #25
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    Faulty inverter boards weren't uncommon in earlier LCD monitors, mostly because of terrible design. You could purchase complete kits of replacement semiconductors for inverter boards. Of course, the silliness in PSU layout was legend. Electrolytic caps hot-glued to heat sinks, is a good example.

  6. #26
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    The stupid yellow adhesive that was used to attach components to the PCB is also an irritating issue.

    It's corrosive, and as it's baked by years of heat, it gets hard and turns brown or black. In this state, it becomes conductive and starts shorting out various parts of the board and has to be removed. I've had to spend hours chipping that stuff off of PCBs, sometimes having to remove dozens of components to get all of it out.

    I've seen the stuff eat components legs completely off, probably as a result of electrolytic corrosion due to it being conductive.

  7. #27
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    Cool. Once it fails again soldering or replacing the power unit board will be the way to go.

  8. #28
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    Has been fine so far from 745AM to 1045AM without flickering or shutting down.

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