Those 381LL are for sure going to last forever, did you just buy them from Newark.com? I had a few in my cart and now they are sold out…..
Last edited:
Naw. Bought from Mouser over a year ago.
Mouser currently has a 100 that can ship immediately. https://www.mouser.com/ProductDetai.../381LL183M050A062?qs=Cb2nCFKsA8pf5Xbf2Z56ZQ==
Mouser currently has a 100 that can ship immediately. https://www.mouser.com/ProductDetai.../381LL183M050A062?qs=Cb2nCFKsA8pf5Xbf2Z56ZQ==
I guess it happened just because any description of a good (or bad) component represents a form of advertising.
It triggers imitative behaviour even though there are so many other good components out there...
Does the leakage increase with time as increase of ESR is also about temperature or is there a natural chemical aging of the cap : chemical ; proof of the polymer base sealing ; electrode interface ; else ; ?
Can I know how is my amp caps after 30 years of service ? I mean, some use their amp one hour a week, some others several hours a day ! Should one desolder it and test them cap by cap ?
Actually, ESR isn't important in the least in audio circuits except maybe for an output coupling cap in single supply designs. You need to look at D/A. For power supply filter capacitors, your oscilloscope tells a complete story. Both the amount of ripple, and the shape of the ripple waveform tell you a lot. Long before an ESR meter will indicate. D/A is also a more sensitive measurement.
Supply filter capacitors have better seals than most others, and a lot more electrolyte. Therefore they tend to last longer than the smaller capacitors with rubber seals where the leads just poke through. Aging in use forms the oxide layer, so leakage current will drop. Expect leakage current to be higher after initial turn on, but rapidly drop depending on how much time passed from the time it was last used. If you don't subject the capacitor to voltage, that layer deteriorates and the next time you power up, there will be current forming to reform that layer. If the cap has deteriorated enough the forming current will be excessive and overheat the capacitor. Sometimes they may vent as a result. The better quality capacitors suffer less from this, but as noted above it does depend on running temperature and run time.
Vintage gear I have tested (30 - 50 years old) have shown that often the filter capacitors are fine. However you will see failures due to age, and also because newer capacitors have better manufacturing and chemistry these days. However that doesn't mean that replacing old caps for new will improve performance. Newer capacitors are often smaller, so you may also have mounting issues. Don't increase capacitance, use a higher voltage part to get into a larger can size.
-Chris
Supply filter capacitors have better seals than most others, and a lot more electrolyte. Therefore they tend to last longer than the smaller capacitors with rubber seals where the leads just poke through. Aging in use forms the oxide layer, so leakage current will drop. Expect leakage current to be higher after initial turn on, but rapidly drop depending on how much time passed from the time it was last used. If you don't subject the capacitor to voltage, that layer deteriorates and the next time you power up, there will be current forming to reform that layer. If the cap has deteriorated enough the forming current will be excessive and overheat the capacitor. Sometimes they may vent as a result. The better quality capacitors suffer less from this, but as noted above it does depend on running temperature and run time.
Vintage gear I have tested (30 - 50 years old) have shown that often the filter capacitors are fine. However you will see failures due to age, and also because newer capacitors have better manufacturing and chemistry these days. However that doesn't mean that replacing old caps for new will improve performance. Newer capacitors are often smaller, so you may also have mounting issues. Don't increase capacitance, use a higher voltage part to get into a larger can size.
-Chris
"Actually, ESR isn't important in the least in audio circuits except maybe for an output coupling cap in single supply designs"
True heat wise. Having used normal capacitor in PC SMPS to stay online until getting a proper low HF impedance part it went very hot. But worked fine in a linear PSU for audio.
True heat wise. Having used normal capacitor in PC SMPS to stay online until getting a proper low HF impedance part it went very hot. But worked fine in a linear PSU for audio.
Hi Salas,
Once ESR reads high, that capacitor is well along the road to failure. Want to scan boards quickly? Use your oscilloscope for filter capacitors. For others, you are into a removal exercise to actually measure that capacitor properly. In circuit it is in parallel with everything else. If you want a real valid reading you have to do it correctly.
When I pull a capacitor, I am replacing it unless it is an expensive type. I measure each so I know what issues I am dealing with and if this could have been a problem. I also get a very good idea of the condition of the rest of like parts in a set. So I know how important it is to check others in locations not stressed or in high temperature areas. This saves time and gives the customer the highest value. Obviously some brands of capacitors just need to be replaced due to demonstrated quality issues.
I pull capacitors that are suspect due to use and circuit location, and also past history in some models or with some brands of capacitors.
ESR? I'm of the opinion you are wasting your time measuring that. You won't catch developing problems, and in circuit you cannot be certain what you measured - not really. I think these are cheap instruments that are advertised as being able to measure in-circuit (the ultimate time saver!). Works in most tube circuits, but not in solid state. It comes down to spending the money for a real capacitor tester that measures real performance and characteristics. That and it takes time. So, both unpopular suggestions to people who want to save money and believe they did a good job.
How many filament testers were sold as "tube checkers"? Then we have emission testers. Better, but do not detect bad tubes unless they are really toast. You need to measure "dynamic mutual conductance" to determine if a tube can do it's job properly. Basically the ability of the tube to amplify. You also need to check gas (leakage) and noise. The same holds true for capacitors and resistors - and active solid state devices. My point is, you can buy inexpensive toys that "test" components. Or, you can buy something that tests capacitor characteristics that are of value at various frequencies and possibly voltage levels - with and without DC bias. ESR meters are toys.
-Chris
Once ESR reads high, that capacitor is well along the road to failure. Want to scan boards quickly? Use your oscilloscope for filter capacitors. For others, you are into a removal exercise to actually measure that capacitor properly. In circuit it is in parallel with everything else. If you want a real valid reading you have to do it correctly.
When I pull a capacitor, I am replacing it unless it is an expensive type. I measure each so I know what issues I am dealing with and if this could have been a problem. I also get a very good idea of the condition of the rest of like parts in a set. So I know how important it is to check others in locations not stressed or in high temperature areas. This saves time and gives the customer the highest value. Obviously some brands of capacitors just need to be replaced due to demonstrated quality issues.
I pull capacitors that are suspect due to use and circuit location, and also past history in some models or with some brands of capacitors.
ESR? I'm of the opinion you are wasting your time measuring that. You won't catch developing problems, and in circuit you cannot be certain what you measured - not really. I think these are cheap instruments that are advertised as being able to measure in-circuit (the ultimate time saver!). Works in most tube circuits, but not in solid state. It comes down to spending the money for a real capacitor tester that measures real performance and characteristics. That and it takes time. So, both unpopular suggestions to people who want to save money and believe they did a good job.
How many filament testers were sold as "tube checkers"? Then we have emission testers. Better, but do not detect bad tubes unless they are really toast. You need to measure "dynamic mutual conductance" to determine if a tube can do it's job properly. Basically the ability of the tube to amplify. You also need to check gas (leakage) and noise. The same holds true for capacitors and resistors - and active solid state devices. My point is, you can buy inexpensive toys that "test" components. Or, you can buy something that tests capacitor characteristics that are of value at various frequencies and possibly voltage levels - with and without DC bias. ESR meters are toys.
-Chris
Scope is good on psu ripple inspection but many times smaller caps fail in other positions. Nothing like extracting a cap for full inspection. Especially for trying leakage. There are good specialized meters with smaller than Vbe test signal to catch gross cap problems on board quickly. Bob Parker's improved version with Kelvin wired probes is very handy. No zeroing procedure for each time it gets powered on. Not very cheap though.
Funny enough as I had in mind a smps when asking !
(Chord Amp... mine should be close to 30 yo !)
I would call on board ESR meters "suspicion meters" to be absolutely fair. By experience they are successful enough for bad caps detective work. Except if in paralleled arrays and when hiding sneaky problems in their developing phase. Nice example the different tube testers you mentioned Chris. Fortunately I have a TV-7 mutual conductance beast for such. One like this guy uses.
Hi Salas,
Well, my point is that many depend on ESR to determine a capacitor's health without looking further. If the ESR indicates bad, then the cap is definitely bad! However it could be bad while testing okay when other tests will show it deteriorating before an ESR test reads off.
Yes, I collect tube testers. I use a Stark 9-66, made under licence from Hickok. You know well why you use such a tester. The same holds true for all components. For caps, I use an HP 4192A, 4263A and ESI 2150 Digibridge and some GR analogue types. I even have the tube type Heathkit, Sprague and a few others. For real detail work I have an HP 4195A with the impedance test kit. That's a Network Analyzer.
Well, my point is that many depend on ESR to determine a capacitor's health without looking further. If the ESR indicates bad, then the cap is definitely bad! However it could be bad while testing okay when other tests will show it deteriorating before an ESR test reads off.
Yes, I collect tube testers. I use a Stark 9-66, made under licence from Hickok. You know well why you use such a tester. The same holds true for all components. For caps, I use an HP 4192A, 4263A and ESI 2150 Digibridge and some GR analogue types. I even have the tube type Heathkit, Sprague and a few others. For real detail work I have an HP 4195A with the impedance test kit. That's a Network Analyzer.
Hi Salas,
I just saw your post re: scope viewing ripple.
The shape of the ripple tells you a great deal, increasing ripple occurs after waveform changes in most cases.
Yes, for capacitors not used as the main reservoirs in a power supply, the scope won't show much unless you see a lot of AC within the range where that capacitance is effective. You have to pull those and test them.
I just saw your post re: scope viewing ripple.
The shape of the ripple tells you a great deal, increasing ripple occurs after waveform changes in most cases.
Yes, for capacitors not used as the main reservoirs in a power supply, the scope won't show much unless you see a lot of AC within the range where that capacitance is effective. You have to pull those and test them.