Fried LT1054


I started to assemble a Shruthi-1 today.
I’m a total newbie when it comes to soldering, but I think it’s been going okay…
…part from that my LT1054 got hot and actually started to smoke.

I was testing the voltages and got 4.7 V from GND to all the red points but 0 V to all the green points.
Now, when I’ve removed the LT1054, I still get the same results - but now I’m getting 0V on all of the 7905 pins.

I’m using a 7.5V DC 2A with center pin positive power supply so that shouldn’t be an issue.

Hmm, help?

Was the LT1054 inserted backwards? Was the polarity of the nearby capacitors correct? Check the voltage that your power supply delivers. 7.5V DC / 2A could mean that it delivers a much higher voltage with less load.

Thank you so much for getting back to me.

I’ve been very careful when putting everything in, so the polarity is correct on all the caps according to the instructions.
The power supply is regulated and has got a switch for V amount. The 7.5V reads about 7.8V in the multimeter and the 9.V is 9.8V in the multimeter.


Same goes for the LT1054, it was inserted correctly.

Can you post pics of both sides of the board in the area of the LT1054 and the 7905 ?

The LT1054 is here removed.
Don’t ask me why, but I haven’t cut any loose ends in the back.

looks like there are a bunch of shorts caused by the loose legs on the bottom.

maybe it only looks like it on the picture and you were carefull about them not touching each other, but at least the caps around ic5 look shorted



EDIT. The right joint from the Diode looks ugly.

Yeah, sorry for being such a total newbie at this wasting your time with questions.
I was careful about them not touching each other, I bent them when checking the soldering.

Now I’ve cut them all so that is not the question anymore (in case I didn’t ruin everything).

Still getting the same values, 4.7V from the red points, 0V from the green points.
Now I get 7.12V from the bottom right pin of the LT1054. 0V from all of the 7905 pins.

Where do I go from here?


Well you can start with a ordering a new LT1054. If there was smoke it’s broken now. And i think it has come from a short of the wires you had sticking out. Even if you were really careful it’s hard not to have made a short that way.

Okay, thanks.

Anything more while I’m at it? A new 7905 as well?