Tips on locating shorts?

[mlabbee]

Gaah!  All soldered up and no sound.  My battery is heating up, which means I have a short (right?). I'm getting ready to go over everything with a fine tooth comb to figure out whether I just soldered something wrong or screwed something up on the PCB - does anyone know any good tricks for locating a short?  This is a TS clone with switching between two clipping stages, true bypass with 3PDT switches and LED indicators.

[Lonestarjohnny]

Down at the Mall this time of the year, all the Girls are wearing them !  :mrgreen:
Seriously though, just look back threw the circuit slowly as you compare the schematic, you'll find your short, sometime's it's just a small trace, hard to see sometime's and make sure your transistors are oriented properly for the pinout used on the schematic,
Johnny

[R.G.]

Yep, I know a couple of shortcuts, but you won't like them.

The simplest in theory is also the hardest to do. Hook an oscillator to the shorted path through some limiting resistor to keep from killing the oscillator. Now the shorted path is singing at the oscillator frequency. Now take a cassete recorder's playback head and hook it onto the end of a shielded cable which is plugged into a high gain amp. Use the cassette head to follow the current. You'll hear the oscillator as long as the cassette head is over the trace where the current is flowing. Works every time.

The simplest to actually do is to use a magnifying glass.

[petemoore]

What a Great way to do that !!!
 Makes sense now that I'm thinking about that.
 "Activating a recording head/playback head would be a good thing to get good at.
 Now that I think of it, all that would be figured out in a tape player, except the extension wires and head removal, maybe shielded wire for the extension.
 Have you ever done that? Seems like you'd at least be able to find what part of the board was 'carrying at least on a tightly strewn circuit, I think tape heads are about 1/2'', of course then you'd only need to use one side of the stereo head...
 When you say short, did you test for continuuity across the battery clip connectors + and - ?
 Sometimes 'something touches ground killing the circuit sound, Ive found these with the DMM beeping on a certain part probed with the other DMM lead to ground.
 I like to check for PS shorts between battery terminal clip, because it'll fry the battery or other stuff when battery's connected.
 I just clip black to ground and check all over the board and pots etc. for ground that shouldn't be..remeber to turn the pots half way so you don't get 'erronious' ground readings off a pot that has another lug wired to ground.

[mlabbee]

Well, thank goodness it was something easy - it was just a screw up wiring in the jacks, so I didn't have to go trace-by-trace.  I did go to the mall, though. Thanks for the tip :-)

RG - that's a great idea.  They do something similar to hook-up phone lines, don't they?  I've seen phone installers clip an oscillator to a line and then check the jacks with a little noise maker that picks up the signal.  Never thought to do something similar for boards - fortunately, I don't need to rig it up today (phew!) but I will keep it in mind for future projects.

[Toney]

Shorts located under pants.
Best to check there first.
If no go, recommend mother/girlfriend/wife.
Excellent resourse for missing shorts.

[Paul Marossy]

In your case, with the battery getting hot, I would use the continuity checker on my DMM to check out all the connections on the power supply. If I hear a beep when I shouldn't, that usually indicates where the short is.

As noted, a good magnifying glass is also very helpful.

[Lonestarjohnny]

Glad you got it goin, and hope you enjoyed the site's at the Mall :mrgreen:
Johnny