Thank you, Im glad it helped you! It's a pretty good concept for anyone working on these radios or tube circuitry in general to learn how to do. I will have more on the way soon!
You're welcome, I'm glad you found it useful. I figured it would be a good topic to cover since it's so simple to do with some basic equipment most people have already.
I love your vintage test setup. I like to work on old tube amps so I am using also vintage test tools, like an old Hameg scope, Philips signal generator and Philips RC meter
Thank you, I'm glad you found it useful! It's a simple and handy test to be able to do. It's a Heathkit model IP-32 regulated high voltage DC power supply.
There are so many ways of tetsting capacitors , from using a simple ohmmeter to digital C comparator and the Weinbridge.The one thing most testers fail to do is see how long the cap holds a charge. Aside from its true value, holding an open circuit charge is the real test.
Hi Doc Brown's Radio Lab, I,m Just starting to try and fixed old Radio, Believe me, Not easy at 62 years old, I have ,Medical Problems,and need to keep Busy, I have alway's wanted to learn, And don't plan on dying any time soon, Anyway, I just bought a old Knight majic eye,Capacitor checker, Could this be converted, into what you have, If I added a step up transformer, with variable capacitor to adjust voltage output, and add a voltage meter in circuit.
The only way to do that, that I know of, is with an oscilloscope. But it is very easy. Set the scope's vertical amplifier to some low volts/division, probably around 10 or 20mV. Time base division doesn't matter, just adjust for a solid trace. Connect the probe's ground wire to one end of the cap and the probe tip to the other end while holding the cap body between your thumb and forefinger-- observe the "noise" on the scope. Now, while trying not to move the cap body between your fingers, reverse the probe connections and again observe the noise. The orientation with the lowest noise will be the one with the ground lead connected to the outer foil side of the cap. I disagree to the comment that this is not important. It's just not that important in all situations, but if you're trying to keep as much noise out of your signal path as possible, I think it's important for bypass caps to be connected with their outer foil side on the lowest impedance path to ground... especially in high gain stages.
"Very leaky".... (i.e., dead short) 🙃 an ohmeter would probably more easily tell you that cap is bad. I don't think DC leakage will always be evident with the setup you're demonstrating. I think this setup will work fine for finding shorted capacitors (of course) of any value, and maybe dc leakage on low value capacitors (and if we're only concerned about leaky coupling caps, maybe that's fine)-- but this setup charges the cap through the input resistance of the vtvm (and if using a dmm, in some cases the input resistance may be much higher than a vtvm). So, if the cap is a large value, you would have to let it sit for a very long time to charge before any leakage voltage would be evident. You might be mislead into thinking it's not leaking, but rather, it's just not charging (and with a dmm, it may never charge). Better to substitute the vtvm with a microammeter and put a current limiting resistor in series with the cap. Then you can read the actual dc leakage current directly. But then there's the whole discussion of, "how much leakage current is okay?" Probably none on small film caps, but it can be upwards of hundreds of microamps for larger electrolytics.
Very clever and easy to do DC leakage test. Thanks for sharing this idea, and looking forward to more videos.
Thank you, Im glad it helped you! It's a pretty good concept for anyone working on these radios or tube circuitry in general to learn how to do. I will have more on the way soon!
Great idea and simply straight forward set-up. Great. Thank you for sharing sir.
You're welcome, I'm glad you found it useful. I figured it would be a good topic to cover since it's so simple to do with some basic equipment most people have already.
I love your vintage test setup. I like to work on old tube amps so I am using also vintage test tools, like an old Hameg scope, Philips signal generator and Philips RC meter
Brilliant, thank you.
Great video! This is a surprisingly simple method. What is the model of that Heathkit power supply you're using?
Thank you, I'm glad you found it useful! It's a simple and handy test to be able to do. It's a Heathkit model IP-32 regulated high voltage DC power supply.
There are so many ways of tetsting capacitors , from using a simple ohmmeter to digital C comparator and the Weinbridge.The one thing most testers fail to do is see how long the cap holds a charge. Aside from its true value, holding an open circuit charge is the real test.
Hi Doc Brown's Radio Lab, I,m Just starting to try and fixed old Radio, Believe me, Not easy at 62 years old, I have ,Medical Problems,and need to keep Busy, I have alway's wanted to learn, And don't plan on dying any time soon, Anyway, I just bought a old Knight majic eye,Capacitor checker, Could this be converted, into what you have, If I added a step up transformer, with variable capacitor to adjust voltage output, and add a voltage meter in circuit.
Great info!
Looking at your gear, I have to ask, "Do I need to buy tubes for this build?" :)
Haha I agree, all of my test gear there is tube based as well. It's all been restored.
Could this set be used to ID the "foil" end of the cap?
The importance of the foil end is in most cases overstated
The only way to do that, that I know of, is with an oscilloscope. But it is very easy.
Set the scope's vertical amplifier to some low volts/division, probably around 10 or 20mV. Time base division doesn't matter, just adjust for a solid trace. Connect the probe's ground wire to one end of the cap and the probe tip to the other end while holding the cap body between your thumb and forefinger-- observe the "noise" on the scope. Now, while trying not to move the cap body between your fingers, reverse the probe connections and again observe the noise. The orientation with the lowest noise will be the one with the ground lead connected to the outer foil side of the cap.
I disagree to the comment that this is not important. It's just not that important in all situations, but if you're trying to keep as much noise out of your signal path as possible, I think it's important for bypass caps to be connected with their outer foil side on the lowest impedance path to ground... especially in high gain stages.
Did you change your name?
Yes, I switched my whole account so that's why things were a little different. I'm still sorting things out.
@@docbrownsradiolab1220 Ah ok, thanks for the response.
"Very leaky".... (i.e., dead short) 🙃 an ohmeter would probably more easily tell you that cap is bad. I don't think DC leakage will always be evident with the setup you're demonstrating. I think this setup will work fine for finding shorted capacitors (of course) of any value, and maybe dc leakage on low value capacitors (and if we're only concerned about leaky coupling caps, maybe that's fine)-- but this setup charges the cap through the input resistance of the vtvm (and if using a dmm, in some cases the input resistance may be much higher than a vtvm). So, if the cap is a large value, you would have to let it sit for a very long time to charge before any leakage voltage would be evident. You might be mislead into thinking it's not leaking, but rather, it's just not charging (and with a dmm, it may never charge). Better to substitute the vtvm with a microammeter and put a current limiting resistor in series with the cap. Then you can read the actual dc leakage current directly. But then there's the whole discussion of, "how much leakage current is okay?" Probably none on small film caps, but it can be upwards of hundreds of microamps for larger electrolytics.
Im not quite sure whom you are trying to impress, but nice vintage test bench though.
All that test equipment for a capacitor and the simplest thing to do is just replace it.
We aren't looking for simplicity we are looking for maximum nerdness.