LT1054 gets hot, Problems with 7905?

Hi!
I’m build the SMR-4 filter board to the point where you check the voltage levels and the 1054 gets hot after a short time. I already found a topic where the issue was solved by resoldering stuff but I don’t think I’ve shortened anything or soldered incorrectly. Could there be a problem with the 7905 and how could I test it? When measuring the voltages at green points, the current keeps dropping from 3 Volts or something (So there might be a soldering problem after all, but I don’t really know where :S)

Maybe some of you can help me :slight_smile:

Cheers

Yo, Zundborg,

in 95% of the Cases it is a soldering problem. As the you only have done the PowerSupply and some caps (that wont cause a problem if not soldered totally weired…) just resolder every Pad. If this doesnt helpt #2 Issue is a faulty 1054, if you have a spare try swapping.

Also, check for shorts between GND and the +5 / -5V rails.

I resoldered all the pads with no success and there are no visible shorts.
I tested again and while the blue and red points keep being stable, the current on all green points drops from 5V (I unplugged the adapter at 2,5V because I’m scared of stuff reaching zero…)

I assume there is no way of testing the 1054 (right?). I think I’ll pay my electronics store a visit and hope they have those.

The LT1054 has nothing to do with the positive rail.

Try removing the LT1054. The points at -5V should be at 0V. If you still see something wrong with the points at +5V, you’ll know the 1054 is not the problem.

I just tested it and the points at +5V kept being stable while the -5V points were at 0V.

And I just realized I should have said “-5V on all green points” in the last post. SOrry :S

What is the voltage on pin 5 of the LT1054?

Uh… it’s already dropping there (starting a little bit above -5V and steadily decreasing).
This means the current isn’t dropping because of the 1054 right? But i can’t really understand why it would get hot then…

If it’s decreasing, there’s something wrong with the LT1054 or one of the part around it. Do the solder joints of all the capacitors around the 1054 look OK?

The soldered pads are all shiny and clean. When I checked this time the current on the middle pin of the 7905 started at -7V and dropped rapidly to -5V.

Just a quick notice:
I replaced the 1054 and it’s working now. Thanks for the support!

Issue #2 :wink:

I’m not really a soldering hero and couldn’t really believe the problem wasn’t my fault :3

:smiley: