LM317/LM337 temperature differences

[AKlein]

I have been using a diy LM317/337 power supply +15/-15vdc supply rails to power a DIY preamp for a few years.

I have noticed, just, that the positive regulator (LM317) is notably hotter than the negative. Both have the same heatsinks/conditions etc.

Is there a reason for this mystery?

 

[davidsrsb]

More load on the +15V than the -15V?

 

[stv]

Or higher + input voltage?

 

[AKlein]

The load is an Elliot Sounds P97 preamp, P05 dual power supply so input voltage is the same.

Everything works, just the heat imbalance.

 

[stv]

so input voltage is the same

I was thinking about input from transformer secondaries into the regulator. Maybe the positive is higher?
You could just measure current draw for positive and negative supply. And measure input voltages from transformer.
Any additional loads connected to the positive rail? E.g. Leds?

 

[AKlein]

Any additional loads connected to the positive rail? E.g. Leds?

Of course,

Yes, LED's, there are 5 of them, albeit in two series sets, 1x2nr and 1x3nr both sets running around 11ma or so, so the regulator has, at least, another 20ma more current than the negative.

Thanks.