I am sure this is a stupid question, but nevertheless:
I have an amp that the original 470uf 80v caps were bulging. there were two of them, I replaced them both with new Panasonic 470uf 80v TS-HA 'large can' caps. They are similarly sized to the originals.
They sit just after a full wave bridge and I noticed that one of them gets warm.
The measured voltage is +80 at one cap and -80 at the other. The polarity is correct and the output is fairly smooth.
In retrospect I probably should have gotten 100v caps, but the last set of 80's lasted many years.
Is it normal for caps to get warm during operation? The rectifier is cooler than the caps.
I have an amp that the original 470uf 80v caps were bulging. there were two of them, I replaced them both with new Panasonic 470uf 80v TS-HA 'large can' caps. They are similarly sized to the originals.
They sit just after a full wave bridge and I noticed that one of them gets warm.
The measured voltage is +80 at one cap and -80 at the other. The polarity is correct and the output is fairly smooth.
In retrospect I probably should have gotten 100v caps, but the last set of 80's lasted many years.
Is it normal for caps to get warm during operation? The rectifier is cooler than the caps.
is there any thing directly connected to it or in electrical contact with the tabs that gets warm? If no, you will probly wanna up the voltage rating. The leakage current at 80V is high enough to make it warm. If your meter says 80VDC, there is probly a ripple voltage component that exceeds the 80V rating. One other thing..is the amp running at high power when you are checking the cap temperature? If they only get warm then, then the ESR is high enough to be causing the temp to rise because of ripple current. Like magura said, lifespan goes down significantly with slight increases in temperature. Best to increase voltage rating anyway.
If your original capacitors were bulging there is most likely a problem with the original power supply circuit.
Old electrolytic caps typically dry out but do not bulge.
Bulging is caused by overheating the electrolyte which causes gas vapors to rise out of the vents in the tops of the caps.
Another possibility is that 80V could be too close to their actual operating level and 100V caps should be used in their place.
Old electrolytic caps typically dry out but do not bulge.
Bulging is caused by overheating the electrolyte which causes gas vapors to rise out of the vents in the tops of the caps.
Another possibility is that 80V could be too close to their actual operating level and 100V caps should be used in their place.
Well the heat is a direct offspring of the series resistance of the cap and the amount of current passing through it, a la ohm's law...
2 solutions, find lower ESR caps..... or find caps with higher ripple current handleing...
A higher voltage cap, normally has lower series resistance, so that is starting to think in the right direction....
2 solutions, find lower ESR caps..... or find caps with higher ripple current handleing...
A higher voltage cap, normally has lower series resistance, so that is starting to think in the right direction....
I think I will go ahead and get some higher voltage, low ESR caps.
The heat is mostly generated at idle. As for the power supply circuitry, it is so simple I can't imagine there is anything wrong. This particular piece is connected directly to the output side of a diode rectifier which is connected directly to the output of a transformer. This particular piece of the supply is low current capable of sourcing only 2 amps.
The heat is mostly generated at idle. As for the power supply circuitry, it is so simple I can't imagine there is anything wrong. This particular piece is connected directly to the output side of a diode rectifier which is connected directly to the output of a transformer. This particular piece of the supply is low current capable of sourcing only 2 amps.
One cap seems to generate it's own heat. I don't see any way that heat is being conducted to it from an outside source unless it is through a trace on the board.
I replaced the cap once thinking that maybe it was defective.
As far as how warm, warm to the touch - but not hot.
Maybe there is a bad diode.
I replaced the cap once thinking that maybe it was defective.
As far as how warm, warm to the touch - but not hot.
Maybe there is a bad diode.
You don't want 80V capacitors with 80V across them - in the long distant past capacitors were rated fairly conservatively, but in any remotely modern times the voltage ratings are VERY tight. If it says 80V you don't want 81V across it!.
So I would get 100V capacitors, low ESR would be good too, and i would suggest getting 105 degree rated ones - I use nothing else these days.
If only one is getting hot?, it may be (as already suggested) that there's a fault causing it, such as a leaky rectifier.
The original failure is very likely to be due to the faulty electrolyte that was used in millions of capacitors a few years back - failure is often accompanied by doming and leakage.
So I would get 100V capacitors, low ESR would be good too, and i would suggest getting 105 degree rated ones - I use nothing else these days.
If only one is getting hot?, it may be (as already suggested) that there's a fault causing it, such as a leaky rectifier.
The original failure is very likely to be due to the faulty electrolyte that was used in millions of capacitors a few years back - failure is often accompanied by doming and leakage.
I replaced all the diodes in the rectifier and the one cap still gets hot. I will go ahead and order a pair of 100v low ESR replacements and use it as is until they arrive.
I did notice that as soon as I turn up the volume a little bit the voltage across that cap drops. I guess I just have to listen loud!
I did notice that as soon as I turn up the volume a little bit the voltage across that cap drops. I guess I just have to listen loud!
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