Heat from Legato

[bigpandahk]

Recently, I accidentally touched the resistors on legato and got burnt. I measure the temperature and surprising me that its over 75 deg C. Further measure those underneath the BIII, they are over 80 deg C. Is it normal? Such heat may damage or shorten the BIII life.

 

[Russ White]

There are no resistors under the BIII... What do you mean?

Which version of Legato? What voltage at the supplies? You have not given many details for us to give you an answer.

An any case - both circuits were designed to be used at their indicated supply voltages. You should not have any issues if you stick to the numbers.

 

[bigpandahk]

Just bought last month, it's the latest version. Power supply are +-15V.

The BIII is stack above the legato, those resistors are on the legato just underneath the BIII.

 

[Russ White]

If you run it like that you should be just fine, but you can adjust the Legato supply voltage down to 12V rails if it makes you more comfortable.

Those kind of temperatures below the BIII should not be a problem for the BIII in any case, because it will not be getting anything close to that hot.

 

[mmerig]

Mine ran hot too, as I was setting it up (balancing off-set, etc). The main problem I have is the rails draw vastly different currents, and the resistance to ground for the V+ rail is about 2K ohms, for the V-, its about 9 Mohms.

I am still trouble shooting it, but it would helpful to know what the rails resistance should be, roughly. Which of the rails on my board has a reasonable resistance?

Thanks.