Well, that would explain a lot; except this: would one dielectric sheet be any different (say, in thickness or chemical composition) than the other? Is the isolation of the two foils supposed to be different in one direction than toward the other side? I'm still confused. One lead of the cap is at a lower impedance, as discussion has shown, than the other; so there's a difference in electromotive potential between the two foils. How does that translate into stored/released energy? How do (presuming they do!) electrons get translated from one foil to the other. As a speculation, I'm answering my first question with a "yes."
Cap outer foil tester build -- Peegoo Custom Special
- Thread starter King Fan
- Start date
I think this is the case. Many diagrams show only three layers in a rolled-up cap example:
There are actually four layers.
There are actually four layers.
They may or may not be. Both act together to keep the plates (foils) separated. The dielectric is 'tuned' to create the specified capacitance.
Some have a dielectric layer and a separator which is made of a different material. The dielectric, however, is what defines the capacitance of the cap.
Here's a rundown on the physics behind the magic.
Thank you for that. What I learned: electrons don't pass the dielectric between the plates. Discharge, and transfer of electrons from one foil to the other happens through the circuit "downstream" (away from the voltage source, the load) from the cap.
I wonder, then, why all the descriptions of film and foil caps make out like there's only one dielectric sheet. And also, how the "tuning" of dielectric operates to establish the capacitance value. At some point does the dielectric, in fact, allow electrons to pass (when charge has built up to some amount), and thus limit the capacitance?
My apologies if this is perceived as having wandered too far from the topic . . .
I wonder, then, why all the descriptions of film and foil caps make out like there's only one dielectric sheet. And also, how the "tuning" of dielectric operates to establish the capacitance value. At some point does the dielectric, in fact, allow electrons to pass (when charge has built up to some amount), and thus limit the capacitance?
My apologies if this is perceived as having wandered too far from the topic . . .
@chas.wahl The dielectric blocks flow of electrons; they cannot pass through a cap. This is why, when a cap is described as "leaky," it means it's leaking electrons (DC voltage) from one side to the other, through the dielectric.
In a capacitor, electrons accumulate on one plate and dissipate from the other. The accumulated and dissipated electrons remain on each side of the insulator; none cross over. This is how AC current works.
You may be confusing capacitor voltage with battery voltage. Even though caps do store voltage, they don't store it like a battery does.
Wanna see something totally cool? I may buy one of these kits. Even when you understand how electronic components work, this is still a bit of a mind blow because it's dead easy to see and understand when it's presented in a mechanical form like this.
The inductor and transistor are particularly fascinating.
In a capacitor, electrons accumulate on one plate and dissipate from the other. The accumulated and dissipated electrons remain on each side of the insulator; none cross over. This is how AC current works.
You may be confusing capacitor voltage with battery voltage. Even though caps do store voltage, they don't store it like a battery does.
Wanna see something totally cool? I may buy one of these kits. Even when you understand how electronic components work, this is still a bit of a mind blow because it's dead easy to see and understand when it's presented in a mechanical form like this.
The inductor and transistor are particularly fascinating.
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I think this is the case. Many diagrams show only three layers in a rolled-up cap example:
There are actually four layers.
Someone needs to invent the Mobius Strip Capacitor.
I thought about that. But it wouldn't work because the insulator has only one side.
Creepy!
ievans
Tele-Meister
Uncle Doug has a pretty great explanation of capacitance & voltage ratings in caps based on the size and spacing of the dialectric material & plates.
OK as promised, I went and tested my old caps, including a bunch of Mallory 150s. A few results:
• Aiken notes smaller caps (like .022uF) make it easier to see the difference on a scope, but since they also seem noisier overall (on average) they may not make it easier to 'hear' the difference; it may even be harder.
• Different cap sizes (in both uF and physical size) seem to have different noise levels -- but again this may not help or hinder testing their end-to-end differences.
• It does mean you want to be selective with your amp volume dial -- some caps are pretty noisy at 4, others only at 7 or even 8.
• The Mallory 150s weren't especially 'hard to tell' with the tester, like they were in the past; in re-testing those I'd formerly marked using the crude gators+plug test, I found I'd got 3 of 10 wrong. I'll say the switch makes testing more accurate as well as easier, quieter, and quicker.
What about the label orientation? I had 15 Mallory 150s, 12 Mojo Dijons, and 3 big huge caps someone out there will recognize.
Yeah, all three of those have the outer foil to the right of the label. But we all know three heads in three coin flips doesn't mean a thing. In fact, neither the Mallories nor Dijons had a consistent relationship of label to outer foil. So testing is necessary; folks are right to say label alone isn't reliable on these brands. (And QC guys will tell you you'd want sample sizes like 30 or better yet 100 before you decided that labels were really reliable predictors).
Fun tip: I'd found it hard to make anything like neat or straight lines on cylindrical caps, but discovered a handy shortcut -- an ultra-fine Sharpie and a rubber band stretched straight...
• Aiken notes smaller caps (like .022uF) make it easier to see the difference on a scope, but since they also seem noisier overall (on average) they may not make it easier to 'hear' the difference; it may even be harder.
• Different cap sizes (in both uF and physical size) seem to have different noise levels -- but again this may not help or hinder testing their end-to-end differences.
• It does mean you want to be selective with your amp volume dial -- some caps are pretty noisy at 4, others only at 7 or even 8.
• The Mallory 150s weren't especially 'hard to tell' with the tester, like they were in the past; in re-testing those I'd formerly marked using the crude gators+plug test, I found I'd got 3 of 10 wrong. I'll say the switch makes testing more accurate as well as easier, quieter, and quicker.
What about the label orientation? I had 15 Mallory 150s, 12 Mojo Dijons, and 3 big huge caps someone out there will recognize.
Yeah, all three of those have the outer foil to the right of the label. But we all know three heads in three coin flips doesn't mean a thing. In fact, neither the Mallories nor Dijons had a consistent relationship of label to outer foil. So testing is necessary; folks are right to say label alone isn't reliable on these brands. (And QC guys will tell you you'd want sample sizes like 30 or better yet 100 before you decided that labels were really reliable predictors).
Fun tip: I'd found it hard to make anything like neat or straight lines on cylindrical caps, but discovered a handy shortcut -- an ultra-fine Sharpie and a rubber band stretched straight...
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LOL, but you're honest. Your note will cheer up @chas.wahl , who's been up nights picturing one conductor lying right on the other. Plus you were nice to keep Mr. Aiken company for a while.
Back at the Peegoo Buckaroo Switcheroo, I trimmed down the clip leads from about 6" to about 4." (I'd originally pictured them sitting neatly on top of that empty side of the box.) In fact 4" is already a bit too short -- you want enough slack and reach that they're easy to clip onto a cap without reorienting the lead in space.
If you're having a hard time with certain caps:
1. Turn up the treble on the amp because some of the noise is hiss that's way up there, and
2. Remember how pedals make noise worse, and players are always looking for ways to eradicate it? Let's buck tradition: put an overdrive or distortobox between the tester and the amp. A wah may also be useful here as well because it's a sweepable-peak envelope filter.
You bought those pedals...you're allowed to use 'em for other stuff besides making music
Your use of banana plugs was a really good idea because it makes the little clip leads movable and removable. These are just under 4" long. I left the 'handles' off the banana plugs because they add bulk; instead, I added heat shrink. I have a roll of silicone test lead wire which was perfect for this. The bent switch tip makes it easier to flip too.
Nice! Looks all-pro.
I’m getting way trivial here, like in 'how many deck chairs can be rearranged on the head of a pin?' But I start to see at least a couple options for test leads.
Shorter, beefier, with gator clips, like yours; caps basically all clip in the same easy obvious way and stay in one basic place. Short, compact, tidy, pro.
Longer, slinkier, with hook grips, like mine. Longer lets you orient the dinky hooks to the cap leads in space and then *move the cap around.* This was helpful when I was testing on top of an amp here; I found laying the cap right across the chassis to squeeze musta supplied some extra EMF, like the old trick of holding the cap across a live power cord. But messy, awkward. Long live the banana plug; at least they’re removable.
When we go into business, we can sell several kinds, $19.95 each or a 'pro pack', all 3 for $57.
I’m getting way trivial here, like in 'how many deck chairs can be rearranged on the head of a pin?' But I start to see at least a couple options for test leads.
Shorter, beefier, with gator clips, like yours; caps basically all clip in the same easy obvious way and stay in one basic place. Short, compact, tidy, pro.
Longer, slinkier, with hook grips, like mine. Longer lets you orient the dinky hooks to the cap leads in space and then *move the cap around.* This was helpful when I was testing on top of an amp here; I found laying the cap right across the chassis to squeeze musta supplied some extra EMF, like the old trick of holding the cap across a live power cord. But messy, awkward. Long live the banana plug; at least they’re removable.
When we go into business, we can sell several kinds, $19.95 each or a 'pro pack', all 3 for $57.
58Bassman
Tele-Holic
Mine is a piece of shielded cable with a 1/4" mono plug on one end and the other end has the shield pulled back & soldered to a piece of black wire, the joint covered with heat shrink tubing and it has a red/black pair of alligator clips. Never thought it needed to be complex and switching the leads doesn't take a lot of time. If I had to check a buttload of caps, I could see making it switchable.
58Bassman
Tele-Holic
Your use of banana plugs was a really good idea because it makes the little clip leads movable and removable. These are just under 4" long. I left the 'handles' off the banana plugs because they add bulk; instead, I added heat shrink. I have a roll of silicone test lead wire which was perfect for this. The bent switch tip makes it easier to flip too.
You could use right angle banana plugs, too.
I've been considering making a single 'universal' clip with two conductors that can handle small and large radial and axial cap leads. One press of a button, stick the cap in.
I know this all seems unnecessarily complicated, but there are a whole lot of folks that don't have a scope.
At that price, you'll be selling them way below basic cost of the components, I think. Oak-Grigsby switch is about $12 retail alone. Then enclosure, terminals (for removable leads), clips and wire, jack. Let's not even begin with "business/approvals" overhead. Sure, you can cheap out on every component, and ignore the business end, but would you sleep at night?
How about a youtube video instead? I thought this one for a light bulb current limiter was a bit fast-paced (about 3 times as fast as Uncle Doug), but certainly comprehensive, with explanations along the way:
58Bassman
Tele-Holic
Permanent connections, or more of a square of breadboard, for repositioning? Or, maybe an IC socket with the arm could be cemented to the box with the connections soldered underneath.
58Bassman
Tele-Holic
Do you think the business can absorb the loss of $.95/unit?
You could use the same motto as 1970s Sony TV dealers, as a joke- "We lose money on every TV we sell, but we make up for it in volume!".
We'll have to come up with some sort of required expendables and sell the box as a loss leader.
Just like ink jet printers and Swiffer mops.
The absolute ultimate Alpha product is toilet paper: it is a single-use item and throwing it away is a critical part of its proper usage.
Just like ink jet printers and Swiffer mops.
The absolute ultimate Alpha product is toilet paper: it is a single-use item and throwing it away is a critical part of its proper usage.
