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How to Build a DCR Measuring Tool

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build one of the most useful DIY guitar tools.

Welcome back to Mod Garage. After receiving numerous requests to show more DIY tools for guitarists, today we’ll explore one of my favorites. For years I’ve used this one in the shop daily and I’m sure you’ll love it. It’s cheap and easy to build, but very effective for analyzing circuits of electric guitars and basses without opening the electronic compartment or lifting the pickguard. It’s a kind of adaptor or extension to measure a pickup’s DC resistance (DCR) from outside the guitar. After building one, we’ll discuss how to interpret the measurements.

The DCR of a pickup is by far the most common parameter you can read when reading pickup descriptions and often it’s used as an indicator of the output. The reason for this is that it’s easy to measure, but, sadly, it doesn’t tell us anything about a pickup’s output nor its tone. To quote pickup designer Bill Lawrence: “DC resistance tells you as much about a pickup’s tone and output as the shoe size tells you about a person’s intelligence.”

I’ve written about DCR as a pickup parameter in detail and you can read about it in “Mod Garage: Demystifying DCR.”

DCR is not a primary parameter in pickup design. It’s simply the result of the type and gauge of the pickup’s wire, the number of turns, and other parameters like the winding pattern, etc. But it isn’t completely useless, and we can use it as a good reference point for analyzing pickups both inside and outside a guitar or bass circuit. All you need for this is a digital multimeter (DMM). You don’t need an expensive calibrated precision DMM—any entry level DMM will work. You can get a simple digital DMM for $10, but if you want to invest in a better device, it can’t harm.

The easiest way to analyze a pickup is outside a circuit. Simply set your DMM to ohm and connect the two pickup leads to your DMM. If your DMM doesn’t have an auto-range function, set it to 20k ohm. Now you’ll get the DCR reading for your pickup. You can compare it to the factory specs of your pickup and it should be close. If your DMM shows “infinite” or “overload,” you know the pickup wire is broken. Let’s say your pickup should read 7k ohm, but yours reads around 2-3k ohm. Your pickup likely has a short circuit somewhere in the winding. Used this way, the DCR is always good to quickly check if a pickup is alive or not.

To quickly analyze a guitar or bass circuit with one or more pickups, you first need to build the DIY adaptor tool this column is about. There are two different versions, and you don’t need much for this:

  • Version #1: This is the quick and dirty version. You need a standard 6.3 mm straight mono plug (the same type on all your guitar cables), some wire of your choice (preferably in two different colors), and two insulated alligator clips.
  • Version #2: A more elegant version that you can also use with a scope if you have one. You need the same parts as for version #1, but instead of two alligator clips, you need two 4 mm banana plugs, and the two wires need to be longer than what you’d use for Version #1.

So, heat up your soldering iron and let’s get to building version #1.

  1. Solder one piece of wire to the HOT terminal of the mono plug and another one to the GROUND terminal. I prefer a red wire for the HOT and a black wire for the GROUND terminal (Photo 1).
  2. Solder an insulated alligator-clip to each end of the two wires, preferably a black one to the black wire and a red one to the red wire. Ready!

Version #2 is built the same way, but, instead of alligator clips, you solder a 4 mm banana plug to each end of the two wires, if possible, also in black and red. The two wires should be long enough that can place your DMM and/or scope at some distance from the guitar. In Photo 2, you can see version #1 on the top and version #2 on the bottom.

The difference between the two versions is that with version #1 you put the plug into the output jack of the guitar, connecting the two probes of your DMM to the alligator clips: the black probe of the DMM goes to ground (black wire) and the red probe goes to hot (red wire) as seen in Photo 3. With version #2, you need to remove the two probes from your DMM, plugging the two banana plugs directly into your DMM or your scope, also seen in Photo 3.

Both versions work equally well. Version #2 is just easier to operate when you also want to use the adaptor for a scope.

For a quick check, you can also directly touch the hot and ground terminals with the probes of your DMM, but you need both hands or a second person for this if you want to play around with the controls or the pickup-selector switch.

Now we can easily check four things with this tool, assuming everything is connected the way it should be and your DMM is set to ohm and auto-range or the 20k ohm scale if your DMM doesn’t have an auto-range mode:

  1. Do you receive a reading on your connected DMM? If not, check if the volume pot is fully opened. Do you receive a reading now? If so, close the volume pot completely and see if you still receive a reading. No? Perfect, you just proved that the volume pot is alive and well.
  2. With a fully opened volume pot and a reading on your DMM, slowly turn down the volume and watch the reading on the DMM. If you receive some crazy reading, chances are good there is a treble bleed network on your volume pot. If the reading slowly goes down to zero, you know that there is no treble bleed network on the volume pot, and you can check if it’s an audio or linear volume pot (plus the taper it has, if it’s an audio pot). Let’s say we have a 500k volume pot. When you close the volume pot halfway and receive a reading around 250k, you know it’s a linear pot. An audio pot, depending on its taper, will result in a much higher reading on the first 50 percent of the volume pot. If you read 500k until the volume pot is almost fully closed, this means the pot has a 90:10 audio taper—exactly the kind of volume pot you don’t want to have. If you read something around 300k in the middle of the volume pot, you know it’s a 60:40 audio taper.
  3. If the volume pot is fully opened and you don’t receive a reading on your DMM, chances are good that your output jack is broken, not connected, or connected incorrectly. Please make sure there is no activated kill-switch in the circuit that can also cause this “problem.”
  4. Turning the tone knob(s) will make no difference in the reading you receive. If you receive a slightly higher reading with a tone pot fully opened compared to when it’s closed, you know it’s a no-load tone pot.

There is a lot to discover from just the outside of any guitar or bass. So, now let’s see what we can measure from outside the instrument starting with a Telecaster with a 4-way switch. The readings in all examples are the readings I received with guitars I had in the shop, but they can be different in your instruments:

  • Bridge pickup only: 5.85k ohm
  • Neck pickup only: 6.76k ohm
  • Both pickups together: 3.18k ohm
  • Pickup selector switch in position #4: 12.30k ohm

The readings for both pickups are within the factory specs and are in a typical range for a vintage-flavored Telecaster pickup set. With a reading of 3.18k ohm for both pickups together, you know that both pickups are in parallel. With the reading of 12.30k ohm, you know that both pickups are in series with each other.

Here is the simplified math behind these readings:

  • Series connection: DCR pickup #1 + DCR pickup #2
    • In our example, it’s 5.85k + 6.76k = 12.61k ohm, which is very close to the reading of 12.30k we received. The missing 0.31k ohm are eaten up by the resistance of the pots and the tolerance of your DMM. For this test, I chose the cheapest DMM I could find in the shop. A calibrated high-quality DMM will have much less tolerance.
  • Parallel connection: (DCR pickup #1 + DCR pickup #2) divided by four
    • In our example, it’s 5.85k + 6.76k = 12.61k ohm divided by four = 3.15k ohm, which is very close to the reading of 3.18k ohm we received.

Now let’s repeat this with a standard Stratocaster:

  • Bridge pickup only: 7.07k ohm
  • Middle pickup only: 5.88k ohm
  • Neck pickup only: 5.70k ohm
  • Bridge + Middle pickups together: 3.26k ohm
  • Neck + Middle pickups together: 2.94k ohm

All three pickups are within the factory specs of this Strat. We have a slightly hotter bridge and two vintage-flavored pickups. The two in-between positions are in parallel.

Lastly, let’s try a vintage PAF-loaded Les Paul:

  • Bridge pickup only: 7.77k ohm
  • Neck pickup only: 7.09k ohm
  • Both pickups together: 3.74k ohm

Both PAFs have the typical vintage DCR and are in parallel in the middle position.

That’s it. Next month we’ll take a deeper look at changing wires on pickups, which is something I’ve been asked about a lot, so stay tuned!Until then … keep on modding!

by Dick Wacker – PREMIER GUITAR

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You’re neither.

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© Fom Tooley 2022 – All Rights Reserved.

Link: https://pin.it/3IcWNgp

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No one is safe: “This tiny $30 device can break into your car and home.”

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hack home security systems with this cheap electronic pussy device / cum

This super-small piece of electronics can hack into your car and home, and it requires only $30 to make. Not everyone wants to accept this simple truth, but that doesn’t make it any less real: hackers outpace security advancements. When it comes to both online security and real-world security, hackers have already devised 10 new tools by the time security researchers come up with an effective way to block one old tool. As a result, no one is ever truly safe — and a new device recently shown off by a well-known security researcher is yet another example of just how vulnerable we really are.

Online and offline security expert Samy Kamkar took to Defcon 2015 to show off a tiny device he calls “Rolljam.” The device is as shockingly simple as it is devious and brilliant, and it can be used to break into just about any car. Worse yet, it can even be used to break into a target’s home.

Rolljam is a tiny series of circuit boards with three in-built radios, Wired reports. It works by using two of the radios to jam the wireless signal sent out by a car’s keyless entry remote, while the third radio reads the code that was transmitted by the remote, which is then stored on the device.

Keyless entry devices use a system of rolling codes to prevent hackers from stealing them wirelessly and reusing them at will. Once a code is used a single time, it cannot be used again — and therein lies the brilliance of the Rolljam device.

Since the device blocks the signal from a car’s key fob while it is being transmitted, the unique code never reaches the owner’s car. The next time he or she presses the unlock button, a new code will be transmitted and it will successfully unlock the car. But that first code was never actually used, so the Rolljam can then transmit it at a later time and it will successfully unlock the target car.

Kamkar’s device was used to successfully unlock cars made by Nissan, Cadillac, Ford, Toyota, Lotus, Volkswagen and Chrysler, and it also worked perfectly with a number of garage door openers, potentially giving the user access to a target’s home.

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Russia’s ‘Vacuum Bombs’ Could Unleash Hell on Ukrainian Civilians, and Amount to a War Crime

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The TOS-1A heavy flamethrower system is meant to take on fortified enemy positions. Used against civilians, it would almost certainly amount to a war crime.

Russian TOS-1A Heavy Flamethrower System

One of Russia’s most deadly and controversial land weapons is the TOS-1A heavy flamethrower.

  • One of Russia’s most deadly and controversial land weapons is the TOS-1A heavy flamethrower.
  • It uses rockets with thermobaric weapons to destroy entrenched enemy troops.
  • Used in Ukraine’s cities, the weapons would do massive damage to military and civilian targets alike, including ordinary people taking shelter from the fighting.

As Russia’s troops grow increasingly bogged down in their invasion of Ukraine, observers are concerned the Russian military could unleash one of its most devastating non-nuclear weapons in civilian areas: the TOS-1A heavy flamethrower system. Originally designed to destroy fortified NATO targets, the TOS-1A is designed to create shattering waves of searing heat and overpressure, killing enemy troops inside bunkers and other reinforced targets.

The Russian Ground Forces have, until Monday, refrained from using heavy artillery in Ukraine’s urban areas. This has been an impediment to typical Russian combat operations, as Moscow’s military doctrine usually prescribes a liberal amount of artillery to batter the enemy before a ground assault. Although there have been numerous sightings of heavy Russian artillery pieces rolling into Ukraine—and reports that Moscow has already used thermobaric weapons against civilians—there have been no official confirmations yet.

All of that may be about to change. Artillery bombardments of Ukrainian cities and towns are becoming increasingly common, with evidence of BM-30 Smerch 300-millimeter rockets, Grad-P 122-millimeter rockets, and other salvo-fired rocket systems in active use. The worst of all, however, is the TOS-1A. As the weapon’s state-owned exporter states in its marketing materials: “I will create hell for the enemy.” No lie detected.

The TOS-1A is a weapon without equivalents in Western armies. TOS-1A and weapons like it are called “thermobaric” due to their use of extreme heat and pressure to incapacitate or kill. The Soviet Union first developed the TOS-1A in the 1970s as a weapon to fulfill the role of a flamethrower, destroying enemy troops in bunkers. At the time, most armies were shifting away from the traditional role of a flame-spurting flamethrower, but there was still a need for a weapon that could somehow reach through the narrow firing ports of a bunker or fighting position to neutralize the troops inside.

A RUSSIAN GROUND FORCES T-90M AND TOS-1A TRAVEL DOWN TVERSKAYA STREET AFTER A VICTORY DAY MILITARY PARADE MARKING THE 75TH ANNIVERSARY OF THE VICTORY IN WORLD WAR I, JUNE 2020...
A RUSSIAN GROUND FORCES T-90M AND TOS-1A TRAVEL DOWN TVERSKAYA STREET AFTER A VICTORY DAY MILITARY PARADE MARKING THE 75TH ANNIVERSARY OF THE VICTORY IN WORLD WAR I, JUNE 2020…

The original vehicle, TOS-1, was designed to carry 30 rockets with a 220-millimeter diameter. Each rocket was packed with inert—but flammable—metal particles, dispersed in a cloud-like pattern at the target. Ideally, the airborne metallic particles filter into hard-to-reach places through firing ports in a bunker, crew hatches in armored vehicles, and cave entrances. The rocket then detonates the cloud, creating a deadly fireball.

The explosion also has a powerful secondary effect: the generation of powerful positive, then negative, pressure waves. The quick succession of positive and negative pressure waves is why some call thermobaric weapons “vacuum bombs.” The pressure differential has a devastating effect on buildings, structures, and the human body—particularly the lungs. The U.S. Air Force’s Mother of All Bombs (MOAB), the world’s largest conventional bomb, similarly kills through overpressure, and in 2017 was dropped on an ISIS cave complex in Afghanistan.

Russian servicemen load 200mm thermobaric warheads onto a TOS-1A vehicle
RUSSIAN SERVICEMEN LOAD 200-MILLIMETER THERMOBARIC WARHEADS ONTO A TOS-1A VEHICLE..

The modern version of TOS-1 is TOS-1A, also known as Solntsepek (Sun). The weapon still uses 220-millimeter rockets, but only carries 24 at a time. According to Rosoboronexport, the state company that markets and coordinates international arms sales, TOS-1A can launch its rockets just 90 seconds after coming to a full stop. It can fire all 24 rockets in six seconds, and a single vehicle can savage 40,000 square meters, the equivalent of almost ten acres. In addition to the Russian Ground Forces, armies in Algeria, Armenia, Azerbaijan, Iraq, Jordan, Kazakhstan, Saudi Arabia, and Syria also operate TOS-1As.

Here’s a video that Russia’s Ministry of Defense uploaded to YouTube in 2019, showing the loading and firing of TOS-1As during an exercise:

Loading and Firing the TOS-1A

TOS-1A’s effects against soldiers are horrifying enough, but against civilians it has the potential for mass slaughter. The dangers to unprotected civilians are obvious, but it can also damage (or even collapse) non-military buildings, killing or injuring those taking shelter inside.

Two human rights organizations—London’s Amnesty International and New York City’s Human Rights Watch—have both claimed that Russia “appeared to have used widely banned cluster munitions, with Amnesty accusing them of attacking a preschool in northeastern Ukraine while civilians took shelter inside,” according to a February 28 report from Reuters, but those claims have not yet been verified.

TOS-1A HEAVY FLAMETHROWERS TEST FIRING IN NORTH OSSETIA, RUSSIA, 2019. A SINGLE VEHICLE CAN DEVASTATE TEN SQUARE ACRES OF LAND.
TOS-1A HEAVY FLAMETHROWERS TEST FIRING IN NORTH OSSETIA, RUSSIA, 2019. A SINGLE VEHICLE CAN DEVASTATE TEN SQUARE ACRES OF LAND..

TOS-1A will devastate civilian populations in Ukraine if Russia uses it against them. Already, Russian rockets are raining down in urban areas in Kharkiv, a city in the eastern part of the country that has managed to hold out against Russian forces despite overwhelming odds. If Putin grows desperate, he might order his military to deploy TOS-1A and similar rocket systems as terror weapons in an attempt to break Ukraine’s morale.

While such actions might have their intended effect, it would also broadly be considered a war crime, and land Putin and his administration in even deeper international trouble than it’s in now.

BY KYLE MIZOKAMI MAR 1, 2022