We took the caps out, connected them to an osciloscope witch showed a graph telling us the input and output voltage of the cap. When 10V was pushed to it on the output you could find the same voltage with only a 50mV drop witch shows it's resistance is minimal and he should still be in great condition. At least that's the explanation i understood.
If i remember well we used an AC square wave with a freqency of 10khz.
The device we used for testing was this thing:
http://www.testequity.com/Images/new/keysight/DSOX4024-825.jpg
Or something very similar
The device we used for testing was this thing:
http://www.testequity.com/Images/new/keysight/DSOX4024-825.jpg
Or something very similar
No, it doesn't sound like it was anything worthwhile though?.
Obviously testing it's ESR with an ESR meter would probably be the most worthwhile test.
So a capacitor in ideal world would not affect the electricity getting trough it. In real world that does not exist and just like any other conductor it resists electricity getting trough it. It's resistance is very small but the capacitor itself can be shown as a combination of an ideal capacitor and a small resistor.
By what the guy explained to me, the older the capacitor gets the higher it's resistance gets, therefore lowering the voltage getting trough the capacitor and generating more heat. The heat dries out the capacitor event faster so it exponentially gets worse and worse because of drying out.
What we were testing is resistance of the capacitor witch has shown to be insignificantly small, meaning the capacitor is still not nearing it's life cycle end.
That's as much as i understood.
You can measure impedance of any device by 1. Hooking it up to a load of a known impedance 2. exciting the device under test (dut) with a sine waveform of known frequency voltage and source impedance 3. Measuring the current and voltage on the DUT including the phase shift.
This requires a signal generator, a load, and a scope.
Then you calculate the DUT impedance using vector algebra.
If you have a signal generator and scope, this is cheaper than buying a ESR meter.
However, old electrolytic capacitors can have rubber seals that work today, and fail tomorrow due to oxidation of the rubber. You can make some prediction by taking the DUT up to operating temperature where the water vapor will pressurize the seal, putting it under stress. This requires, a load resistor to put the amp at maximum output, or an enviromental chamber to put the removed capacitor at the proper temperature, plus the test setup or meter.
If I've taken the amp case off and removed the boards and unsoldereds the capacitor because the amp has problem, I just change the **** e-capacitors. I use ones with service life >3000 hours from five vendors known for high quality caps.
At home, I just run audio equipment until it fails, although bad sound and or low power may happen long before a no output fault happens.
Other organizations I attend, just sell off old equipment that might fail and buy new ones every ten years. America is the throw away society, after all. If you are a pro sound DJ, then you are in that category. Replace 15 year old e-capacitors, fans and pots, or trade off the amp, is my advice. New amps won't generally be capable of being economically repaired, consisting of surface mount components and proprietary parts like microprocessor containing copywrited firmware, but that is in general what consumers want. The organization I'm a member of loves their new shiny Behringer and other import equipment, and the salesman that sells it to them with a beautiful smile. The nine year old equipment of a similar source that started failing during meetings, well, "it was old". Meanwhile at home I listen to and make beautiful music with equipment 20-54 years old: with some new parts like e-capacitors, pots, fans, occasionally a tube or resistor.
This requires a signal generator, a load, and a scope.
Then you calculate the DUT impedance using vector algebra.
If you have a signal generator and scope, this is cheaper than buying a ESR meter.
However, old electrolytic capacitors can have rubber seals that work today, and fail tomorrow due to oxidation of the rubber. You can make some prediction by taking the DUT up to operating temperature where the water vapor will pressurize the seal, putting it under stress. This requires, a load resistor to put the amp at maximum output, or an enviromental chamber to put the removed capacitor at the proper temperature, plus the test setup or meter.
If I've taken the amp case off and removed the boards and unsoldereds the capacitor because the amp has problem, I just change the **** e-capacitors. I use ones with service life >3000 hours from five vendors known for high quality caps.
At home, I just run audio equipment until it fails, although bad sound and or low power may happen long before a no output fault happens.
Other organizations I attend, just sell off old equipment that might fail and buy new ones every ten years. America is the throw away society, after all. If you are a pro sound DJ, then you are in that category. Replace 15 year old e-capacitors, fans and pots, or trade off the amp, is my advice. New amps won't generally be capable of being economically repaired, consisting of surface mount components and proprietary parts like microprocessor containing copywrited firmware, but that is in general what consumers want. The organization I'm a member of loves their new shiny Behringer and other import equipment, and the salesman that sells it to them with a beautiful smile. The nine year old equipment of a similar source that started failing during meetings, well, "it was old". Meanwhile at home I listen to and make beautiful music with equipment 20-54 years old: with some new parts like e-capacitors, pots, fans, occasionally a tube or resistor.
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What you explained in the first 2 rows is exactly what we did. Pushed known voltage in a form of a sinewave at a know frequency from a source of a known impedance, trough a capacitor and then the scope showed us the voltage drop that cap causes (or in the other words, the impedance of the cap).
But i don't know how to explain this well because i'm a sound engineer, not an electrotechnician, my friend who is an electrotechnician did the testings while i watched.
And yes, i'm kind of shocked by how simple these old amps are. All the parts are so easy to reach and replace. Today things like this don't exist anymore.
I am probably going to run these amps untill i hear a significant performance drop. Then i will be replacing caps because this big ones are not that cheap at all.
But i don't know how to explain this well because i'm a sound engineer, not an electrotechnician, my friend who is an electrotechnician did the testings while i watched.
And yes, i'm kind of shocked by how simple these old amps are. All the parts are so easy to reach and replace. Today things like this don't exist anymore.
I am probably going to run these amps untill i hear a significant performance drop. Then i will be replacing caps because this big ones are not that cheap at all.
What was the load?
You have given us the frequency of the sqw, the voltage input and a voltage output.
I need help with one more thing.
Guys from peeckersound just told me my amp is stable at 2ohms stereo / 4 ohms bridge.
But on the back of my amplifier it's written "4ohms" near each connector and then 8ohms bridge. Is there any way to check if an amp is stable at 2 ohms stereo and 4 ohms bridge withouth damaging the amp or the speaker?
Guys from peeckersound just told me my amp is stable at 2ohms stereo / 4 ohms bridge.
But on the back of my amplifier it's written "4ohms" near each connector and then 8ohms bridge. Is there any way to check if an amp is stable at 2 ohms stereo and 4 ohms bridge withouth damaging the amp or the speaker?
stable and able to drive are very different.
An amplifier can be stable, i.e. does not oscillate, when connected to a resistive dummy test load.
An amplifier that is capable of driving a reactive speaker load and does not damage itself is a different specification.
You can have an amplifier that is capable of driving a 4ohms reactive speaker load and it is stable when driving a 2r0 resistive test load.
That means you do not connect a 2ohms speaker load.
If you ignore the reactive speaker loading recommendation, you have no recourse when it blows up. You would have abused the equipment and your guarantee will not cover abuse !
An amplifier can be stable, i.e. does not oscillate, when connected to a resistive dummy test load.
An amplifier that is capable of driving a reactive speaker load and does not damage itself is a different specification.
You can have an amplifier that is capable of driving a 4ohms reactive speaker load and it is stable when driving a 2r0 resistive test load.
That means you do not connect a 2ohms speaker load.
If you ignore the reactive speaker loading recommendation, you have no recourse when it blows up. You would have abused the equipment and your guarantee will not cover abuse !
When you bridge a pair of amplifiers the maximum output voltage is effectively double what each single amplifier puts out.
If you double the load impedance, then the doubled voltage will drive the same current into the doubled load impedance from the bridged pair of amplifiers.
Now look at that in a slightly different way.
A bridged pair of amplifiers will give double the power into double the load.
The TOTAL power output from the bridged amplifier is exactly the same as the TOTAL maximum output of the two single amplifiers.
A bridged amplifier does not magically deliver more power !!!!!! read that again. It is important.
Very many Members here and an even higher proportion of the general audio public believe that a bridged pair of amplifiers magically deliver three to four times the power. They are all wrong.
You get double the voltage into double the load impedance from TWO amplifiers.
If you double the load impedance, then the doubled voltage will drive the same current into the doubled load impedance from the bridged pair of amplifiers.
Now look at that in a slightly different way.
A bridged pair of amplifiers will give double the power into double the load.
The TOTAL power output from the bridged amplifier is exactly the same as the TOTAL maximum output of the two single amplifiers.
A bridged amplifier does not magically deliver more power !!!!!! read that again. It is important.
Very many Members here and an even higher proportion of the general audio public believe that a bridged pair of amplifiers magically deliver three to four times the power. They are all wrong.
You get double the voltage into double the load impedance from TWO amplifiers.
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The problem is, i don't have a specsheet/speaker loading reccomendation. There is a high possibility these amps are able to run continuous 2 ohm loads but i can't know for sure.
So the question is, how do i find out withouth destroying something?
And yes, we are not talking peak loads, if they can run 4 ohms bridge/2ohms stereo. I will when i get the first chance bridge each one of them and connect it in parralel with 2 8 ohm RCF L18S800 drivers. And then expect them to do 8 hours of dnb bassline rape at the limits of clipping.
So i can only do this if the amp has a continuous stability rating at these impedances.
The things i know are, the next generation that came after these amps that i have ARE 2 ohm stereo stable (continuous). Guys from peecker sound claim that my TVA amps have same specs as the generation that came after them.
But on the back of my amp this is written:
http://i30.photobucket.com/albums/c316/athlon-64/IMG_2514_zpsxdaltatb.jpg
What do you think about this and how can i test for sure if my amp is 2 ohm stereo stable withouth having a specification sheet of any kind.
So the question is, how do i find out withouth destroying something?
And yes, we are not talking peak loads, if they can run 4 ohms bridge/2ohms stereo. I will when i get the first chance bridge each one of them and connect it in parralel with 2 8 ohm RCF L18S800 drivers. And then expect them to do 8 hours of dnb bassline rape at the limits of clipping.
So i can only do this if the amp has a continuous stability rating at these impedances.
The things i know are, the next generation that came after these amps that i have ARE 2 ohm stereo stable (continuous). Guys from peecker sound claim that my TVA amps have same specs as the generation that came after them.
But on the back of my amp this is written:
http://i30.photobucket.com/albums/c316/athlon-64/IMG_2514_zpsxdaltatb.jpg
What do you think about this and how can i test for sure if my amp is 2 ohm stereo stable withouth having a specification sheet of any kind.
I didn't fully understand you. I'm going to try and simplify what i understand so then correct me if i'm wrong.
Let's assume my amp has got these specifications:
2x500w @8ohms
2x800w @4ohms
2x1000w @2ohms
1x2000w @4ohms bridge
So, guys from peecker sound claim these are specs of my amp because it had the same specs as the next generation for witch they have a datasheet.
Assuming that is correct, we are in the next situation:
I have 2 horn loaded 8ohm 18inch subs.
So far i have been connecting them stereo, each one on it's own channel, witch means they would get a maximum of 500w each.
Now, if i connect both of those subs in parralel, both of them together will present a 4 ohm load.
Then i connect both of them parallel to the amp in bridge mode.
So now we have a 4 ohm load bridge connected to the amplifier.
The amp can push 2000W at 4 ohms if bridged.
That means both of them together will be getting a maximum of 2000w now / 1000w each box. This is twice as much compared to stereo connecting.
Witch part did i get wrong?
There's the first question: Why does it appear to be current crippled into 2r0 resistive loading? That is a warning!
The second is more subtle.
The max voltage into 8r0 test load is 63.2Vac, the max voltage into 4r0 test load is 56.6Vac
The maximum has dropped by 0.96dBV
The amplifier is struggling to drive current into the 4r0 test load. 4r0 is near the limit for this amplifier. That's your second warning !
This specification is telling the truth. The two amplifiers can do a maximum of 1000W+1000W into 2+2ohms and the bridged amplifier can do exactly the same total power of 2000W into 4ohms.
If the amplifier is labeled as 4ohms capable then you risk blowing it up doing ordinary duty bridged into 4ohms . PA duty into 4ohms is asking for trouble.
Who refunds the customers when your amplifier shuts down?
Quote:
This specification is telling the truth. The two amplifiers can do a maximum of 1000W+1000W into 2+2ohms and the bridged amplifier can do exactly the same total power of 2000W into 4ohms.
Yes but right now it's doing only 500w per channel into 8 ohms! That's why i'm saying i'm possibly only using half of it's potential by wiring it the wrong way.
If we were in situation where i was running 4ohm subs, one per channel, then i would allready be using 900w per channel and that is the amps maximum power. So i would have no headroom of getting more out of it and bridge connecting would make no sense.
BUT i'm running 8ohms per channel and getting only 500w per channel / 1000w total.
What i'm trying to do is finding a way to make this amp put it's maximum power output of about 2000w total into two 8 ohm subs.
Now, Yes, i asked this hypotetical to check if i'm getting it right and that if the amp was stable 4ohms/bridge i would be able to get more power out of it.
Now comes the question of IS IT capable of being raped at 4ohms bridged withouth blowing up.
Do you know any way of testing this withouth destroying the amp?
This specification is telling the truth. The two amplifiers can do a maximum of 1000W+1000W into 2+2ohms and the bridged amplifier can do exactly the same total power of 2000W into 4ohms.
Yes but right now it's doing only 500w per channel into 8 ohms! That's why i'm saying i'm possibly only using half of it's potential by wiring it the wrong way.
If we were in situation where i was running 4ohm subs, one per channel, then i would allready be using 900w per channel and that is the amps maximum power. So i would have no headroom of getting more out of it and bridge connecting would make no sense.
BUT i'm running 8ohms per channel and getting only 500w per channel / 1000w total.
What i'm trying to do is finding a way to make this amp put it's maximum power output of about 2000w total into two 8 ohm subs.
Now, Yes, i asked this hypotetical to check if i'm getting it right and that if the amp was stable 4ohms/bridge i would be able to get more power out of it.
Now comes the question of IS IT capable of being raped at 4ohms bridged withouth blowing up.
Do you know any way of testing this withouth destroying the amp?
If your assumed specification is correct, then in my opinion you should not be doing PA bridged into 4ohms.
Do you realise that 2000W into 4ohms is only 3dB more than 500W+500W into 8+8ohms?
Do you realise that the output from the speakers will probably be only 2dB louder after taking account of power compression? Or maybe worse.
Have you looked at using the amp bridged into 8ohms?
Then a second amp bridged into 8ohms will give you more SPL and you now have redundancy in your PA system. The customers might not notice when one amplifier shuts down.
Do you realise that 2000W into 4ohms is only 3dB more than 500W+500W into 8+8ohms?
Do you realise that the output from the speakers will probably be only 2dB louder after taking account of power compression? Or maybe worse.
Have you looked at using the amp bridged into 8ohms?
Then a second amp bridged into 8ohms will give you more SPL and you now have redundancy in your PA system. The customers might not notice when one amplifier shuts down.
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