I have a 20 year old Kinergetics SW200 subwoofer/crossover amplifier that currently uses two 10,000uf 75v storage caps. I wanted to refresh these and was interested in increasing the storage. How high do you think I can increase this? Can I double it to 20,000uf each or should I play it safe and maybe try two 15,000uf caps? I appreciate any advice offered. Thanks.
You should be able to double it without a problem, if the newer components fit then Bob's your uncle 
The only thing i'd do is pay attention to the rectifier or bridge feeding the capacitors, possibly upgrading that will pay dividends & might well be needed as the current pulses into bigger caps will be heavier. It'd make things a tad more efficient & possibly prevent the demise of the rectifiers/bridge that is already fitted You probably won't gain a lot as the limiting factor might well be the transformer, but it certainly won't do any harm.
Nothing like building things like a tank
The only thing i'd do is pay attention to the rectifier or bridge feeding the capacitors, possibly upgrading that will pay dividends & might well be needed as the current pulses into bigger caps will be heavier. It'd make things a tad more efficient & possibly prevent the demise of the rectifiers/bridge that is already fitted You probably won't gain a lot as the limiting factor might well be the transformer, but it certainly won't do any harm.Nothing like building things like a tank
You should be able to double it without a problem, if the newer components fit then Bob's your uncle
Nothing like building things like a tank
Thanks. It's a huge toroidal xformer so I'm thinking it will work well.
Hopefully the rectifier can handle it. I assume that if it can't, it will blow fuses at power up?
Also, I'm new here so I have to ask... who's Bob? Does he sell caps?
Sorry, "Bob's your uncle" is an old english saying meaning "it's not a problem". You might pop a fuse at startup but you are more likely to blow the rectifier if it can't handle the pulsed current through it, that's why i mentioned a possible upgrade. The transformer should be ok as it will have a certain primary & secondary resistance so will to a greater extent self limit the output current it can supply. Be careful of the rectifier though, it might well experience peak current pulses that could short the diodes & then the input fuse will definately blow.
LOL. Got it. Uncle Bob is good....
I took a look at the rectifier and it's a Fagor FB2502. The datasheet can be found here.
FB2502 Datasheet pdf - 25 Amp. Glass Passivated Bridge Rectifier - Fagor
So does it look like it should be replaced or is Bob my uncle with this rectifier? ;}
If you think it should be replaced, what would you recommend? Thanks!
I took a look at the rectifier and it's a Fagor FB2502. The datasheet can be found here.
FB2502 Datasheet pdf - 25 Amp. Glass Passivated Bridge Rectifier - Fagor
So does it look like it should be replaced or is Bob my uncle with this rectifier? ;}
If you think it should be replaced, what would you recommend? Thanks!
Old capacitors should be measured before considering them defective. Typically, large can capacitors have extremely long life, as high as 10.000 hours at 105ºC and many times more at lower temperatures, while the tiny electrolytics are the ones with shorter life. On the other hand, you should think twice before disposing big capacitors in good condition because they contain gentle amounts of toxic substances inside.
To compare the ability of different diode bridges to whitstand inrush current, compare the Ifsm and I2t ratings. There are better bridges than the Fagor with 500A Ifsm and 1100A^2s I2t (GBPC35 from IR).
To compare the ability of different diode bridges to whitstand inrush current, compare the Ifsm and I2t ratings. There are better bridges than the Fagor with 500A Ifsm and 1100A^2s I2t (GBPC35 from IR).
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I wouldn't bother unless you use at least twice the capacitance, and 10mF (per rail?) is quite wimpy for the typical amp. I added 60mF per rail to the existing 23mF - so 3.6 times more - in my Acurus 100W amp, and now it SLAMS. Fortunately it already had a thermistor, so the fuse doesn't pop on turn-on. The rectifier bridge will only see more current for the split second it takes to charge the extra caps, so I wouldn't worry there (but you should prob consider a thermistor on the primary).
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And that's what makes the problems...the pulses are huge currents. One can be glad that not more manufacturers use Schottky bridges which are especially sensitive to overload. If these blow, they straightly short and reversed polarity fed into the amp is when the real fun starts. The usual Si based stuff is more forgiving.
A new and more powerfull bridge is not expensive.
Have fun, Hannes
Ok guys, give me some examples of what I should buy as I'd like to find a vendor that sells the caps and the rectifier I need. So far Eva (thanks), recommended the GBPC35 which I believe is a Vishay.
Also, the rectifier is heavily soldered in. Should I follow suit or use crimp connectors that some recommend. Thanks.
Also, the rectifier is heavily soldered in. Should I follow suit or use crimp connectors that some recommend. Thanks.
Hi,
adding a slow charge circuit to limit the current peak at start up is worth doing anyway. It is even more useful if you intend increasing the smoothing capacitance.
I would suggest at least doubling the smoothing capacitance if you have space and using a pair of relay bypassed Power Thermistors in the secondary to protect both the caps and the bridges at start up.
However, 100V 105degC 20mF caps are not cheap, if you can find a supplier. Multiple 10mF will not be cheap either.
adding a slow charge circuit to limit the current peak at start up is worth doing anyway. It is even more useful if you intend increasing the smoothing capacitance.
I would suggest at least doubling the smoothing capacitance if you have space and using a pair of relay bypassed Power Thermistors in the secondary to protect both the caps and the bridges at start up.
However, 100V 105degC 20mF caps are not cheap, if you can find a supplier. Multiple 10mF will not be cheap either.
As always people have their own (usually much more expensive) alternatives, but something like the 35A GBPC35 bridge that was already mentioned should do (a 6 Euro part). Don't skimp on the voltage rating (say twice what you need, if you don't know what you need take 200V parts or even larger).
Have fun, Hannes
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Which bridge would you choose from here? The current rectifier is an "A" type.
GBPC35
Also, does it matter that the amp uses a single power chip per channel and relays that I hear engage at turn on? I just want to make sure the amp, with a new rectifier, would then be up to the task of handling twice the filter capacitance.
GBPC35
Also, does it matter that the amp uses a single power chip per channel and relays that I hear engage at turn on? I just want to make sure the amp, with a new rectifier, would then be up to the task of handling twice the filter capacitance.
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Hi Monjul, yes i'm sure it'll be fine
What you have done by increasing the capacitance is lower the ripple voltage on the power supply, this will give you a tad more power output (nothing really significant trust me). The capacitors will retain more of there initial charge voltage so under heavy load the voltage rails will be slightly higher, because of this the rectifier will have less time to charge the capacitors & the consequence of this is that the current pulses will be narrower but increased in amplitude.
So with less time to charge the caps the peak current through the rectifiers will increase. I wouldn't fret over the transformer, that'll self limit to a good extent - it's due to both the primary & secondary winding resistances. It'll be fine
What you have done by increasing the capacitance is lower the ripple voltage on the power supply, this will give you a tad more power output (nothing really significant trust me). The capacitors will retain more of there initial charge voltage so under heavy load the voltage rails will be slightly higher, because of this the rectifier will have less time to charge the capacitors & the consequence of this is that the current pulses will be narrower but increased in amplitude.
So with less time to charge the caps the peak current through the rectifiers will increase. I wouldn't fret over the transformer, that'll self limit to a good extent - it's due to both the primary & secondary winding resistances. It'll be fine
More than likely you will not have to concern yourself with new rectifiers as the limiting factor for current supply is your transformer. Both old and new capacitors will effectively behave as a short on charge up as far as the transformer is concerned.
I agree with event horizon you probably will not notice much difference if at all. Even gaining 10% in voltage will only give you a fraction of a dB in your SPL.
I agree with event horizon you probably will not notice much difference if at all. Even gaining 10% in voltage will only give you a fraction of a dB in your SPL.
Thanks for the input Gentlemen.
The main reason I am replacing the caps is because of their age. After hearing the jaw-dropping difference when I recently refreshed the old caps in my Cary tube amp, I decided that the sub amp had to be next as the bass sounds wooly nowadays.
After some price checking, the 18k caps weren't much more expensive than the original 10K value caps so I figure why not? The replacement rectifier is only $5.
So I guess my only questions are:
Should I solder the new rectifier in like it is now with the old device, or should I use crimp connectors as some have suggested on a different forum?
Will the ugraded rectifier sound better because it might be "faster"?
And, should I power up with no load just in case? I can't afford new SEAS woofers!
Thanks again for your expertise.
The main reason I am replacing the caps is because of their age. After hearing the jaw-dropping difference when I recently refreshed the old caps in my Cary tube amp, I decided that the sub amp had to be next as the bass sounds wooly nowadays.
After some price checking, the 18k caps weren't much more expensive than the original 10K value caps so I figure why not? The replacement rectifier is only $5.
So I guess my only questions are:
Should I solder the new rectifier in like it is now with the old device, or should I use crimp connectors as some have suggested on a different forum?
Will the ugraded rectifier sound better because it might be "faster"?
And, should I power up with no load just in case? I can't afford new SEAS woofers!
Thanks again for your expertise.
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Hi again, bolt the new rectifier to the heatsink & then solder the connections to it as per the old wiring. Make sure it's wired up correctly Replace the capacitors & again check that they are wired correctly!
Have a cup of tea or coffee & then check that all is wired correctly at least one more time Then throw the mains switch...Unloaded is probably safer if only for your own state of mind.
It's really pretty easy
Replace the capacitors & again check that they are wired correctly!Have a cup of tea or coffee & then check that all is wired correctly at least one more time
Then throw the mains switch...Unloaded is probably safer if only for your own state of mind.It's really pretty easy
Thanks. I didn't notice a heatsink the first time I unscrewed the rectifier to find the model number. It just seemed to be tied down to the bottom cover. But I have an assortment of small sinks and thermal paste from old PC's. Should I try to incorporate these onto or under the new rectifier? The new rec datasheet says it has an internal heatsink if that matters.
I asked about the soldering because the original is soldered with about 5lbs of solder per terminal, lol. I hope my iron and solder sucker are up to the task!
I asked about the soldering because the original is soldered with about 5lbs of solder per terminal, lol. I hope my iron and solder sucker are up to the task!
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