I have a Sam Coupé and the last time I turn it on, i noticed a smell of components overheating. After opening the power supply I came to the conclusion that is the resistance R1 (50ºc with IR thermometer).

I took the power supply to two technicians who measured the values in the components and the final output. Both said that everything was fine and that the resistance in question was made to warm up. However I'm worried about the situation because I had never noticed this smell before.

Is this heating really normal?

Can someone with a Sam confirm?

Thanks for the help.

Power Supply

  • 2
    50C isn't particularly hot for a 4 Watt resistor. It looks pretty much like this one farnell.com/datasheets/… which will handle the full power up to 70C, and has a maximum temperature rating of 350C, not 50C! – alephzero Feb 15 at 21:33
  • I used my childhood Sam virtually every day for probably several years but have no recollection of a smell from the PSU. – Tommy Feb 15 at 23:43
  • Hi, thanks to both of you. Today i give it a try. I turned on the Sam and used it for about 2 hours, apparently without problems. The PSU continues to smell to hot components. I also noticed that the diode D4 (the first one over the R1 resistor) also heats up a lot (about 60 ° C). The resistance reached 50ºC but was always close to that value. – Bruno Vilela Feb 16 at 18:30

50ºc is nothing for a 4W power resistor, so the 'overheating' smell was probably coming from something else.

As this power supply has a single-sided pcb (tracks on the bottom side only) I would examine all the joints and resolder any that look cracked or burnt. You might also consider testing the electrolytic capacitors for ESR and capacitance value, or just replace them anyway as a precaution.

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