e-licktronic Forum

I'm about half-way through the build. When hooking up the board to the power, I accidentally laid the power board on a piece of solder wire, shorting one of the 2200uF caps. Now my -15V power is misbehaving. It drops lower and lower (I turned it off at -19) and the negative regulator gets very hot.

I hope this is just a matter of replacing whatever part(s) I broke, but I have no idea where to start. Anyone got an idea?

Update: 5V and +15V look fine, that is why I think it is just the -15V.

I am going to start by ordering a set of replacement parts for the -15V power: 2x 100 nF ceramics, 2x 1N4004 diodes, 100/35 electrolytic, 2200/35 electrolytic, LM7915 regulator.

Might be able to save a little money by desoldering and testing components first. I fried my 7915 in a similar way. In was the only component harmed during the incident...

Thanks FactoryDefault! I already ordered the parts; it is not so much money and it takes several days for them to come. I would rather buy a few parts I don't need than wait 4 days after every part.

I already started desoldering some parts; I took the 2200uF (C7) and the LM7915 off. Unfortunately I lifted one of the pads of the output pin of the LM7915. I wonder if I can jumper it to something, or if it will be OK with only half the pad.

Here you see the LM7915 output pin pad on the top side is out (I still have it but not sure if I can push it back in). The caption says 'track' but I meant 'pad'.

[resize=640]https://s3-eu-west-1.amazonaws.com/yoct ... .34.00.jpg[/resize]

Here you see the pad on the bottom is not sitting well anymore either. The caption says 'track' but I meant 'pad'.

[resize=640]https://s3-eu-west-1.amazonaws.com/yoct ... .35.58.jpg[/resize]]

Edit: track -> pad

Looking at the solder side of the board and at schematics of similar power supplies such as http://www.musicfromouterspace.com/anal ... SUPPLY.php I think the output pin of the LM7915 is supposed to connect to three things:

- left leg of C10
- bottom leg of D3
- left leg of D5

That would mean three jumper wires. I am not really looking forward to that, I hope I can salvage the solder side pad of the output pin.

Edit: now that I think about it, a jumper to the left leg of C10 might be enough, because the tracks still run from C10 to those other points.

I reached out to Vincent from e-licktronic and he was nice enough to send me a picture of the schematic of this section of the board. He also confirmed what I wrote above about which components to connect to.

I received my new components and installed the replacement LM7915 and 2200uF/35V capacitor. Now the power works again! I am very relieved. I won't know if there are other problems until I finish the build (just started the Cymbal section) but all the test points on the IC's look good.

While inserting the new LM7915 I ended up lifting the track, but the track seems to be intact.

[resize=640]http://yocto-e04b97363876c567e1fb.s3.am ... .05.47.jpg[/resize]

I attached the output pin of the LM7915 (that needs to connect to the track I lifted) to the nearest diode with a jumper.

[resize=640]http://yocto-e04b97363876c567e1fb.s3.am ... .05.23.jpg[/resize]

Pardon the dust and the workmanship. This is the first time I made such repairs to a circuit board.

I updated the title of the thread because I think this is now resolved. Yay!

jvq wrote:I would rather buy a few parts I don't need than wait 4 days after every part.

Good point. I've placed too many mouser orders where the shipping cost more than the parts...

Glad you got the problem solved.