ShortSniffer Frequently Asked Questions

(and answers)

 

Finding specific bad components:

Q: On my PCBA, there are a lot of caps connected to ground.  Will your product help sniff out shorted Cap?

A: The ShortSniffer injects an audio current which follows the path of least resistance or impedance.  If the shorted caps are lower impedance than the good caps, more current should flow through the shorted caps and the ShortSniffer can probably identify the larger current flowing through the shorted cap.

Q: Can it find shorts in coils and capacitors?

A: Shorts in coils are extremely difficult to locate since each turn of a coil is a DC short circuit to every other turn.  If the coil is large enough that the test current flowing in individual turns can be sensed by the ShortSniffer, a shorted turn will be sensed as a lack of signal in that turn.  The current that should have been flowing in that turn took the path of least resistance, through the short, bypassing that turn.  The location of the short can be sensed by rotating the ShortSniffer ShortSniffer’s probe to be parallel to the current path, giving a null to the sounds of the test current.  While moving around the coil, continually adjusting the probe’s rotation while listening to the lack of sounds, the location of the short can be heard as the probe passes the location of the short where the current flows across the short, at right angles to the normal current flow path.

Shorts in small-valued capacitors can easily be found with a ShortSniffer.  As the value of the capacitors increase, the test currents will more easily pass through good capacitors in parallel with a bad (shorted) capacitor, confusing the troubleshooting process.  The sounds of the current flowing through a 2uF capacitor or through a 10 Ohm resistor are similar.  The Slope Control switch may make it easier to distinguish the current path through parallel components.  The practice board tutorial demonstrates these relationships.

 

Finding problems on general purpose circuit boards (Motherboards, Laptops, Phones, Game consoles)

Q: I don’t have a schematic of any PCB board is that is bad.  Can I can find a short on this board?

Q: Can I use the ShortSniffer to find a short on an iPhone logic board?

Q: I am interested in a short circuit finder that will speed up the repair process on multi-layer Laptop motherboard PCBs.

Q: I work on arcade boards and I think that would help me out.

Q: Can we use for computer desktop & laptop motherboard?

Q: Can it find shorts in Mobile Phone Circuit boards ICs?

Q: Please let me know if I can use SS3 to find out defect/shorted component in a used PCB and not after production line.

A: ShortSniffers were designed to find solder bridges and PC board faults on boards that have just been produced.  These assembly related short circuits and PC board faults are found in prototypes and production units that have never worked because of shorts that occurred during the assembly process.  These faults are common and the ShortSniffer is the best tool for this job. Circuit boards that have failed in the field often have other problems that are not short circuits, so the ShortSniffers operating principles may not be as useful for those boards.  If your problem is really a short circuit, the ShortSniffer should be able to find it after the shorted nets have been identified.  Your biggest problem is to determine which nets are shorted together.

Boards that have failed in the field (with shorts) are often obvious, with holes in components and discoloration on the board where the short event occurred.  The only use I have had for ShortSniffers on boards that have failed in the field was for systems where the power supply had over-voltaged the ICs and melted many of the large-scale logic (CPU, RAM, ROM, etc.).  I could tell that current was going into all the VCC leads on many of the parts.  With many complex parts shorted out, the boards were not worthy of repair, since the cost of replacing the individual parts was more than a replacement board.

ShortSniffers do work for SMD board components and are good for tracing the short circuit currents, even on inner layers, since the pickup head senses the E/M field of the audio test current.  Since the test current follows the path of least resistance, you can follow the sound to the short.  I have traced “invisible” shorts to within 1mm and then used the microscope to see the hairline short (and fix it with an X-ACTO knife).

You can see the ShortSniffer in action at http://www.shortsniffer.com/ShortSniffing.htm.

The ShortSniffer will not be able to locate the failed component unless you already know which nets are shorted.  You must know which nets are shorted so you can inject the test current into those nets, allowing the ShortSniffer to follow the sound to the short.  The initial determination of which nets are shorted is usually done with an ohmmeter and/or oscilloscope.

Please check the continuity testing brush at http://www.tequipment.net/WavetekMetermanSF10.html.

I have used this product for tracing the continuity of unknown boards.  You can achieve similar results by attaching a brass brush (Home Depot paint department) to a circuit continuity tester

Q: I am a small repairer doing power amp repairs and some motherboards.

Q: I currently have my electronics repair shop and need a trustful component fault tester.

A: The ShortSniffers are designed to find faults caused by manufacturing problems.  They may not be the best tool to find problems on circuit boards that worked at one time, then suffered some kind of component failure.  Typical coil shorts are between adjacent windings of the coils, making very little resistance change, but drastically increasing the high-frequency losses in the part.  Most capacitor shorts do not drop to very low resistances, so they are difficult to identify with the ShortSniffer.  The only IC problems I could identify with my ShortSniffers are when the power supply fails with a high voltage, melting the silicon in one or more of the parts.  The ShortSniffers can identify those parts that are shorted.

If you do have a need for locating shorts that can be identified as true short circuits with an ohmmeter, the ShortSniffer is the right tool, able to locate the exact spot where the short is occurring.

The ShortSniffers were not designed as component fault testers but do occasionally work for that purpose.  For instance, if 4 FETs are in parallel and one is shorted, the ShortSniffer can show you which one.  Usually, failed components don’t go to short circuits (below 10 Ohms), so the ability of the ShortSniffer to follow the current (sound) to the short can’t help with that type of troubleshooting.  The main use for ShortSniffers is for finding PC board faults or solder shorts during first-power-up troubleshooting in a manufacturing environment.

 

Is the ShortSniffer better than the Leak Seeker?

Q: Is it better than leek seeker 82B?

A: The LeakSeeker looks like a fine product.  Although I’ve never used a LeakSeeker, the videos are impressive.  I think the ShortSniffer might be better for many manufacturing needs.  The LeakSeeker does require contact with the shorted trace to verify the resistance, while the ShortSniffers only require contact to the two shorted nets for current injection.  The ShortSniffer’s inductive pickup probe can follow the current to the short circuit under components and on inner layers since it does not require contact with the current path to follow the sound to the short.  You can see the ShortSniffers in action on the ShortSniffer website (http://www.shortsniffer.com/ShortSniffing.htm).

Power and Ground plane problems

Q: I have a 4-layer board, where the power input is shorted to ground.  But the ground has the whole layer as ground. The power input of 48V is exposed. In this case, will the short sniffer be useful when the whole board will beep because of the ground plane?

A: The SS2 was designed for locating short circuits on multi-layer boards with power planes

Ground plane shorts can be found with relative ease in about half of the cases, with the difficult ones taking more practice.  Most customers are getting the SS3 Pro Kit because of the three different pickup probes. The Sensitive Probe often makes the difference between success and failure on the most difficult ground plane shorts.

My favorite plane short story is about a customer with a 3-foot square, 32-layer board with 100 BGAs (1000 pins each) and a power-to-ground short.  With a little phone help and his stubborn persistence, he located a place at the corner of the board where there were no components or traces, but a slight dimple where the short had occurred (most likely, something was dropped on the board, causing the short).  With his trusty Dremel, he was able to abrade through the board layers to remove the short and was able to take his prototype to the next day’s trade show.

 

General questions about ShortSniffer operation, characteristics, performance, and specifications

Q: Do you have the ShortSniffer Pro still available as shown on your website?

Q: What is the delivery time?

A: The ShortSniffer SS3 Pro Kit is in stock and can be purchased using a credit card or PayPal in our shop.

Q: Importance: High

1) What is the Resistance range that ShortSniffer can operate on?

2) What ohm resolution does each resistance range have?

3) What voltage level is applied?

A: There are no ranges for the ShortSniffer, although there are Drive and Gain controls to address special conditions beyond the standard solder bridge and PC board defect shorts.

The ShortSniffer injects audio frequency current pulses (about 170Hz) into the short circuit.  The maximum applied (user adjustable) peak current pulses through the output drive capacitor are about 1A, while applied voltage is limited by a pair or back-to-back Silicon diodes for higher resistance shorts.

The ShortSniffer can trace “shorts” above 1k Ohms, as long as the parallel capacitance is not too high, but was optimized for low resistance shorts, including power plane shorts. You can see some of the ShortSniffer Practice Board exercises at:

http://www.shortsniffer.com/ShortSniffer_Practice_Board.htm, and videos at http://www.youtube.com/user/ShortSniffer.

Q: Was searching online for testing equipment to use for RF/MRI product and wanted to ask a few questions about 2 of your items:  ShortSniffer SS3 or SS2

I’ve read the online information regarding the products and noticed the SS3 does indicate being utilized within circuits with inductors and capacitors; is this same concept applied to SS2?

Being that the product will primarily be used for PCB for MRI product(s) that have more inductors/capacitors/diodes and transistors/FET’s I was more interested the SS2, since it doesn’t indicate you have to use other equipment: oscilloscope, power generator, etc. and being that this is equipment I don’t have at my disposal would that be doable for good circuit board issues?

A: The SS2 was the previous high-end product.  It has been replaced by the SS3, which has been optimized, enhancing performance at the extremes of functionality.  For most shorts, any of the ShortSniffer models work very well, following the sound to the short.  The SS3 has adjustments to minimize the shunting effects of parallel capacitors and semiconductors, along with improved gain for the most difficult power-plane shorts.  The SS3 also can indicate the direction of current flow, using stereo headphones and LEDs on the probes.  In most cases, all you need to know is which nets are shorted together, and then the ShortSniffer will help you find the location of the short.

Q: I have a question about working near and around ESD devices. Has the ShortSniffer SS3 been qualified to work near ESD sensitive devices? If so, could you pass that info to me?  We work in a very sensitive area.

A: The ShortSniffers are not specifically designed with ESD reduction components.  The plastic case may cause static build-up when moved across non-conducting surfaces.  The same can be said of the insulators on the current injection cables, the USB cable for the probes, the probe heat-shrink tubing, and the cable for the headphones.

The test current drive system has been specifically designed to work with unpowered electronics circuitry.  The voltage applied to the circuit being tested typically drives into a short circuit, so the applied voltage may only be millivolts.  Under conditions of high resistance shorts (up to 1k Ohms), higher voltages may be applied.  The drive circuitry has a pair of back-to-back silicon diodes across the output terminal, limiting the applied voltage to less than 1 volt.  This level is typically lower than that required to turn on the input protection circuitry of most integrated circuits.  This voltage is also less than what is typically applied by multi-meters in “diode test” mode.

Q: I saw some videos about your product and I would like to know if it can do a continuity test with its probe?

A:  The ShortSniffer requires continuity (a current flow path) to work, so it does perform continuity tests, but is much less convenient than an ohmmeter or beeper, since it also requires the pick-up probe to sense the current flow from the test signal generator leads.  Can you let me know more about your testing needs so I can help you determine if the ShortSniffer is appropriate for your task?

 

Specific troubleshooting approaches

Q: I was wondering if there is any tutorial available to find shorted nets.

A: A voltmeter and ohmmeter are the usual troubleshooting tools for locating shorts.  Following the schematic signals while looking for the area where things go wrong is the usual method for boards that have never been powered up before, and don’t work right.  For a board that has been working, a short circuit is not usually the problem.

Here is a video showing a process of finding shorted nets on a board with shorted data lines on a microcontroller:  https://www.youtube.com/watch?v=oJQq5_gqkqM

And here is information on the practice board that comes with the ShortSniffers:

https://www.youtube.com/user/ShortSniffer

http://shortsniffer.com/ShortSniffer%20Practice%20Board%20Instructions%20_production%20rev%201_.pdf

Q: I have a shorted power bus and have isolated it to an area of the board and have removed the closed components on the board.  The power bus in question is a large internal layer copper pour with vias (both ground and power are internal) that tap into as required I would like to rule out the possibility of internal short to a via.  I would not be able to trace.  Would the ShortSniffer be able to detect a short of this nature?  If so, what would be the process for examining the via?

A: The original ShortSniffers were designed for general purpose short circuit locating.  Most of the enhancements of the SS3 were added to help with the most difficult power plane shorts.  The current spreads out in the power plane, becoming difficult to follow, but it must come back together at the short circuit location.  If your initial connection for the current injection happens to be at the location of the short, you won’t be able to sense the location, since it is right next to the current injection wires.  Moving the current injection points to the other side of the board will usually allow you to locate the short as the only other place the noise can be heard.  Occasionally, you may have to remove large bypass capacitors across the same plane, since they will also provide low impedance current flow paths.

The only power plane board that foiled my attempts at short circuit location had shorts at every power or ground via on the board.  You can see the pictures at the bottom of the page at http://shortsniffer.com/ShortSniffing.htm.  This page also has links (at the top of the page) to videos showing some of the SS3 features by using the practice board.

Q: We have already purchased a model SS3 and I am trying to set this equipment up in our system for use by our trouble shoot technicians.  I have a question concerning preventive maintenance.  What is the expected battery life for this model?

A: The ShortSniffer SS3 draws about 30mA from the 9V alkaline battery.  It will operate properly as the battery discharges down to the 6V to 7V range.  The published alkaline battery discharge curves indicate approximately 20 hours of continuous use before a new battery becomes non-usable.  Please let me know if you need more information.

 

Solar Cell production troubleshooting

This (attached) was super hard to photograph with the lighting we had.  It’s a semicircle where the blue insulation lines have been turned a brownish (sometimes purplish) color.  These make the short sniffer scream, and when I remove all of the insulation lines (including silicon below) in these areas the overall power output of the module increases by about 10%.

I’m sending to you the cells and modules that I’m just tired of looking at.  There are two sets of two unlaminated cells on the bottom. One of those cells has an arrow to one of these spots that is shunting current.

I have no idea what is wrong with the other modules.  I probably could find the problems now after 12 hours of staring down a dissecting scope, but I’m so tired of looking at those modules I figured I’d send them your way.

The ShortSniffer is good at detecting bad modules.  Usually, once I get it to stop screaming the module is finally fixed to high power output.

Thanks for your help!  The short sniffer is so useful!!!

 

Voltage Probe

Q: What is the voltage probe used for?

A: The ShortSniffer Voltage Probe was developed to take advantage of the very high (and non-linear) gain of the ShortSniffer amplifier chain.  The probe provides an AC coupled and voltage limited signal to the input stage of the amplifier chain.  This probe is the only ShortSniffer accessory that is intended to be used on circuits that are powered up and operating.  For safety reasons, do not contact any areas that are operating above 50V, since that is the rating of the AC input capacitor.  The signal is amplified, and presented to the user, with the headphone output being most useful.  Analog signals over the range of 10uV to 10V can be heard with the headphones.  Even with signals that may have frequencies beyond the response of the headphones, there are often low frequency (audio) components that can be heard, whether because of non-linear processing (diode junction detection), of intermodulation byproducts.

Lots of gain . . . now what?  I have used the voltage probe, and have had reports of successes for the following purposes:

1:  The thermal printer in an interactive set-top box was causing video artifacts (snow) during printing.  Using the Voltage Probe, I could hear the pulses on the printer power line.  Following the power trace away from the printer, I heard the pulses beyond the first bypass capacitor and continued to hear the pulses past the next few bypass caps as I progressed to the power supply.  Changing the first cap from 1uF to 50uF reduced the noise so it wasn’t heard past the first cap, and eliminated the video noise.

  1. The OSU Solar Car racing team was assembling modules of cells, laminating them into shapes that fit the shell of the car. Some of the modules were intermittent showing significant efficiency losses.  By placing the Voltage Probe on the panel output and shining a bright light on the panel, monitoring the sound while tapping a stick on the hand-soldered (by student volunteers), the less-than-perfect solder joints could be identified.  A little X-AXTO knife work allowed the defective contacts to be re-soldered, restoring the panel to full functionality.
  2. An Ethernet module for a home-battery power system was having intermittent reboots, with the service technicians making module substitutions without success. One engineer grabbed his ShortSniffer Voltage Probe system and began randomly probing around between the intermittent system and a non-intermittent system.  He was amazed at the difference in noise he heard on the power supply of the intermittent system.  Swapping the power supply, he heard much less noise on the power rails, and the problem “disappeared.”

You can often hear signals that you can’t easily detect with your voltmeter or oscilloscope.  Next time you are confused in a troubleshooting task, set the other tools aside and probe around the design with your ShortSniffer and Voltage Probe.  You may be surprised at what you hear and the insights you can gain.