Originally posted on Dave Mac’s Window on the World: In an amongst the guitar building I decided to break out the soldering iron to build an …
A DIY valve overdrive pedal
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DIY valve overdrive pedal
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Long Island Iced Tea Recipe
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How to Build a DCR Measuring Tool
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.
- 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).
- 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:
- 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.
- 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.
- 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.”
- 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
This is what one town in Ukraine looks like after Russian troops withdrew:
In the devastated town of Borodyanka, northwest of Kyiv, Natasha Romanenko has pushed paper into the bullet holes peppered across her windows.
It’s to keep the cold out, she tells us.
“You can see, there are holes where they were shooting directly in our window when we were hiding there,” she says, speaking through NPR’s interpreter.
When Russian forces invaded and occupied the town, the damage was devastating. Ukrainian officials say Russia deliberately bombed civilian areas and that hundreds are still missing more than a week after the invading forces withdrew. Now, crews are sifting through the wreckage to see what — and who — survived.
We start to see signs of the destruction on the drive from Kyiv into Borodyanka. What should be a quick trip now takes hours as destroyed bridges mean more cars crowd onto the few reliable routes, and the military checkpoints create long lines on narrow roads.
We pass through the village of Dmitriovka and see a burned-out car near homes reduced to rubble. A little farther on, there is a flattened tank.
Then, another destroyed car that has the word “children” spray-painted in Russian along the side door.
We arrive on Borodyanka’s main street — Central Street — with a humanitarian convoy that immediately begins handing out food and water.
It’s here that we meet Natasha. She and her family spent a month hiding in a cramped, dark root cellar.
“What did we eat? Mostly potatoes,” she says. “I had some spare oil, and I have a cow, so I had milk. And I went to my neighbor, I gave her some milk. She gave me some other things, some cheese. So this is how we survived. Our cow saved us.”
Natasha takes us to the cellar, which is mostly filled with crates of potatoes. She explains that at night, they would lay a carpet over the crates and try to sleep on top of that, keeping warm under all the blankets they had.
In the final days of the occupation, Natasha says, a Russian soldier confronted her. She had ventured out to milk her cow, and he thought she was scouting Russian troop locations. She says he took her out to the middle of the road and pointed a gun to her head.
“He was threatening me,” she says. “And what did I say to him? I said I just wish one thing: that he would see my face for the rest of his days, so he would never forget what he’s done here.”
The soldier spoke to someone else on his radio. Then, Natasha says, he let her go.
As the aid workers move through the main street, we break from the group, and the scale of the destruction starts to sink in. It’s utter devastation everywhere you look.
There’s an apartment building blackened from flames, with the middle collapsed from the bombing. The windows in all the storefronts have shattered and roofs have collapsed. There are burned vehicles in the streets, and most of the power lines are down and frayed on the ground.
Across from the destroyed apartment building, there’s a small park with a monument in the middle. On top sits a giant bust of Taras Shevchenko, the famous Ukrainian poet. Bullet holes pierce his forehead.
The tall pillar that the bust rests on is cracked and crumbling from all the shrapnel. Three policemen are holding a ladder while another man stands nearby, ready to climb to the top.
Yaroslav Halubchik is an artist from Kyiv and has come here to help create an ad hoc art project — an instant memorial of sorts.
“We’re calling it ‘The Curing of Shevchenko’ or ‘The Healing of Shevchenko,’ ” he says.
Yaroslav steps up the ladder and starts to wrap a big gauze bandage around the bust’s giant head. As he does that, a man in a Ukrainian military uniform comes up and asks him what he’s doing.
Yaroslav explains that it’s performance art, and the soldier seems satisfied. It turns out, he was worried that they were repairing it.
“In this case, it is vital that we keep this monument as it is right now, it shouldn’t be touched,” the soldier says. He adds that it’s especially important because of who Shevchenko was.
“This is really important, because we all know that Shevchenko and other Ukrainian poets were always enemies of Russia,” he explains. “I really hope that people will rebuild everything here as it was, but we should keep this as it is now.”
We ask his name. He’s Yevhen Nyshchuk — the former Ukrainian minister of culture. He’s in the military now and based nearby.
We keep making our way down the main street. Building after building has collapsed from the bombardment of tank and rocket fire.
In the nearby town of Bucha, bodies were found in the street. Here, with so many collapsed structures, the worry is that bodies are still trapped underneath.
Several cranes carefully pick up debris, as recovery teams look for remains. There’s a playground in front of one of the buildings and a woman is sitting there on a bench next to a slide, watching the recovery work.
Her name is Ludmila Boiko.
“My sister and her son lived here. This is what’s left of them,” she says, pointing to a pile of old notebooks. “His mother kept his old notebooks from school.”
Ludmila found them scattered around the debris of the apartment building. That and some pictures, she says, are the only things she’s found.
Ludmila’s sister Olyna Vahnenko was 56. Her nephew, Yuri, was 24. He had just graduated from college.
They’d left their apartment and sought shelter. But on March 1, during a break in the shelling and bombing, Olyna and Yuri went back. Ludmila says they talked on the phone, and Olyna said they had been able to shower and eat some food.
An hour later, Russian forces destroyed the building.
“Our friends were trying to help us, but for four days, it was a huge fire here,” Ludmila says. “And so first they were trying to fight the fire. They didn’t have a chance to do excavations right away.”
When the fire stopped, people started trying to look for survivors. Then shelling began again, and they had to flee.
After that, she says Russian forces were posted here, and nobody could get near the building.
Searching couldn’t resume until a month after the attack. So Ludmila sat, and waited.
“I just want to see how they discover all the bodies that they assume should be there, and then probably I would like to do something like with DNA testing because I want to know for sure what happened,” she says.
“I was so close with them that I don’t even know how I should live now. How should I live in this place?”
The crane continues to slowly remove rubble from a collapsed building.
Soon, workers discover a woman’s body. Ludmila climbs up the pile of rubble to look.
The body is removed, covered and placed next to three others found earlier that day.
Ludmila goes back to the playground and sits down, continuing her vigil.