Power supply temprature question

Lkaskel · Aug 29, 2019

Hi Gang,
I have 2 identical Robyn SB-520's. They both are pulling .4 amps at idle (19 LSB). They are both set at 13.8 VDC. One of the power supply's is running about 30 degrees higher than the other. I am measuring it at the heatsink near the regulator. I measured it with a fluke digital thermometer. You can feel that it is hotter as well.

Any thoughts why?

Thanks as always!!!

OldTech03 · Aug 29, 2019

You may suspect Electrolytics leaky, shorted etc?

Lkaskel · Aug 29, 2019

OldTech03 said:
You may suspect Electrolytics leaky, shorted etc?

I forgot to mention. Fully re-capped. Thanks OldTech03!!!!

Shadetree Mechanic · Aug 29, 2019

Did it do this before you recapped it? Maybe you got one in backwards?

nomadradio · Aug 30, 2019

Does the power transformer have the same part number in both radios?

Two ways to make that kind of voltage regulator run hotter.

1) Pull more current. But both radios are showing the same.

2) Increase the unregulated voltage feeding into the regulator. The difference between the unregulated DC voltage and the regulated output is called the "pedestal". The higher this voltage is, the more heat you'll throw per Amp of current draw. But if both radios have the same transformer, that can't be it.

A puzzle, for sure.

73

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Power supply temprature question

Lkaskel

Well-Known Member

OldTech03

Sr. Member

Lkaskel

Well-Known Member

Shadetree Mechanic

Delaware Base Station 808

nomadradio

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