EEVblog Electronics Community Forum
Products => Test Equipment => Topic started by: raftronik on November 18, 2021, 04:40:14 pm
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Hello,
I just bought this device Philips PM5133S function generator, I am a bit concerned about the temperatures of several elements marked in the picture, resistors 110 degrees Celsius, transistors 60 degrees Celsius, resistors 55 degrees Celsius.
The generator seems to be working properly but 110 degrees Celsius on resistors is probably way too much.
Does anyone have this generator and could check the temperature of the elements marked in the picture?
Thanks.
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Is the mains voltage switch (selectable by solder links) installed correctly?
Total consumption should not be more than 38 W.
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According to the service manual, the two resistors that you are measuring 110 degrees on are used in the power supply circuit as bypass resistors across the 78xx and 79xx regulators to reduce the power dissipation on those regulators. They are 68 ohm wirewound resistors and I would fully expect them to get real hot. The 60 and 55 degree measurements don't bother me.
You probably should still do a quick check on the voltages surrounding the two regulators. Check with a voltmeter and an oscilloscope just to be sure the power supply is working correctly.
And despite the high temperature, it looks from your photo as though the board hasn't even discolored underneath. I've seen cases where not only was the board discolored brown, but the board actually started to melt.
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Nothing out of the ordinary. The two resistors are mounted well above the PCB and there are holes below them for letting air through. Make sure there is an unrestricted flow of air to the instrument and you hould be fine.
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I checked the voltages and everything seems to be ok with the diagram, I just prefer my equipment not to be too hot.
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Just stay out of the Philps FG if you can't stand the heat. ;D
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If it still a stress concern
Just find the same value resistors with a doubled wattage / same tolerances and you can put some heatsink models on the transistors casings, be sur they dont touch themselves, unless the case is common on the pcb layout ??
But if it aint broke, dont touch nothing