Oh ****, I just blew up U4.

[grandpastar]

I connected the battery box to the circuit board for the first time and when I flipped on the power switch the IC at U4 blew in half!(top piece only) The two pots where connected to the board but not the coil or audio jack. I don't see any shorts (like solder) or any other visible damage. Any ideas or suggestions? Or is it too late. The board is/was complete.

[Qiaozhi]

I connected the battery box to the circuit board for the first time and when I flipped on the power switch the IC at U4 blew in half!(top piece only) The two pots where connected to the board but not the coil or audio jack. I don't see any shorts (like solder) or any other visible damage. Any ideas or suggestions? Or is it too late. The board is/was complete.

I assume you didn't read the part in the Build Documentation where it says:

"If you go through the following steps carefully, and in order, you will have a greater chance of
ending up with a detector that actually works. Please do not proceed to the next step until you have
solved any problems encountered in the current step. If you get stuck at any stage during the build,
then seek help in the Geotech forums before moving on. Do not simply populate the whole board;
discover it doesn't work (which will be the most likely result) and then post in the forums: “I've
built the Minipulse Plus, and it's not working. What's wrong?” …. as you will receive little
sympathy from other Geotech members."

[grandpastar]

I did read that and that's not what happened. I will admit that I'm a novice at this stuff. I thought since I am giving a specific problem maybe there was some hope. If not, then I'll assume it's too late.

[Qiaozhi]

I did read that and that's not what happened. I will admit that I'm a novice at this stuff. I thought since I am giving a specific problem maybe there was some hope. If not, then I'll assume it's too late.

Anything is repairable, given enough time, experience, and the necessary tools.

I assumed you hadn't read that particular section of the Build Document, since you said "I connected the battery box to the circuit board for the first time", and then finished with "The board is/was complete".

There's no shame if that's what happened, as you wouldn't be the first, and probably not the last.

This first thing to do is to identify why you've managed to release the magic smoke.
So, here's some questions:

1) Was the battery pack connected with the correct polarity? (This may sound a stupid question, but it does happen.)
2) Are all the ICs inserted the correct way round? (Also happens a lot.)
3) Are the ICs in sockets?

That will do for a start.

[turboaleks]

I made a stupid mistake and conntected the battery like on page 18 in rev. d document instead of page 11 (vice versa). after replacing power regulator everything was fine again.

[Qiaozhi]

I made a stupid mistake and conntected the battery like on page 18 in rev. d document instead of page 11 (vice versa). after replacing power regulator everything was fine again.

Hmmm ... no-one has ever mentioned that before.

It appears that Fig.14 (page 18 ) is incorrect.
Fig.2 (page 11) shows the correct battery connections.
I suppose that those who have worked their way through the document will get to Fig.2 first, and then not notice the error in Fig.14.

I will correct that one right away, and post an updated Rev-D Build Document.

[grandpastar]

Yes to all three.(like fig.2). The voltage, by the way, reads 12.6. I also don't see anything suspicious on the back side of the board.

[Qiaozhi]

Yes to all three.(like fig.2). The voltage, by the way, reads 12.6. I also don't see anything suspicious on the back side of the board.

In that case I would suggest removing U4 (which has clearly expired). Also, unplug all the other ICs, except U2 and the voltage regulators. Then do a continuity check across PL1 inner and outer pins. Reconnect the battery, without U4 inserted, and check the +5V and -5V supplies.

[grandpastar]

This should be interesting. I did as you said and when I check the continuity it's good for about two seconds and then stops. It's good again if I switch the probes for about two seconds and shuts off again. When I connected the battery pack, the battery pack started to smoke! Now what?

[Qiaozhi]

This should be interesting. I did as you said and when I check the continuity it's good for about two seconds and then stops. It's good again if I switch the probes for about two seconds and shuts off again. When I connected the battery pack, the battery pack started to smoke! Now what?

In that case it's fairly obvious that you have an intermittent short somewhere. If you put an ammeter in series with the battery, you will more than likely register a high current. To debug this problem, a bench power supply (with a current limiting feature) would be better than the battery pack.

After the battery "smoking" episode, did any of the components on the PCB feel hot?

Next I would remove C1 (1000uF), as it's directly across the battery.
If the problem persists, remove U1 (79L05).

[grandpastar]

Thanks for all the help Qiaozhi, but I'm gonna order a new kit, take what I've learned, and go from there. I'm also redoing my power supply with a PCB. Thanks again.

[Qiaozhi]

Thanks for all the help Qiaozhi, but I'm gonna order a new kit, take what I've learned, and go from there. I'm also redoing my power supply with a PCB. Thanks again.

OK - good luck with the new build.
If it wasn't so expensive to send stuff from the US to the UK, I'd ask you to send me the broken board for analysis, so that we could all understand what happened.