Hello
I am new to electronics and need a bit of advice. I hope someone could enlighten me. I am about to replace two electrolytic capacitors on my Sherwood RD 6405 receiver's power supply. It is humming, and the caps look a bit swollen upon a visual inspection. They have obviously gone bad.
The original caps which I am about to replace are 6800 uf capacitance, 63 v voltage. The brand is Samwha.
I do not have a data sheet for these caps, so do not know the ripple current value or ESR.
My main query is, can I assume a new pair of capacitors would work ok as long as they have the same capacitance and voltage (and similar dimensions, of course)? Not knowing the ripple current and ESR of the original caps, can there be serious incompatibilities which could cause damage???
I hope someone could enlighten me. Would be much appreciated! Thanks in advance.
Vlad
I am new to electronics and need a bit of advice. I hope someone could enlighten me. I am about to replace two electrolytic capacitors on my Sherwood RD 6405 receiver's power supply. It is humming, and the caps look a bit swollen upon a visual inspection. They have obviously gone bad.
The original caps which I am about to replace are 6800 uf capacitance, 63 v voltage. The brand is Samwha.
I do not have a data sheet for these caps, so do not know the ripple current value or ESR.
My main query is, can I assume a new pair of capacitors would work ok as long as they have the same capacitance and voltage (and similar dimensions, of course)? Not knowing the ripple current and ESR of the original caps, can there be serious incompatibilities which could cause damage???
I hope someone could enlighten me. Would be much appreciated! Thanks in advance.
Vlad
Same capacitance, voltage rating and physical size should be OK. If they are rate for 85 Degrees C it wouldn't hurt to upgrade to 105 degrees, those tend to have a higher ripple current rating. And of course if the originals are 105's, replace with the same.
Mike
Mike
as the sizes of recently made caps become smaller, you may even get away putting a 10kufd in there....
Thanks heaps Michael.
I am thinking about going for a pair of these (see link below). they are exactly the same size as the original (3cm diameter, 5 cm high).
| 6800μF 63 V dc Aluminium Electrolytic Capacitor, 20% |
also these at the bottom have the same capacitance and voltage, but the dimensions are slightly different (35 mm diameter, 40 mm height).
LGU1J682MELC | 6800μF 63 V dc Aluminium Electrolytic Capacitor, 20%, GU Series | Nichicon
the brand seems a bit more famous, maybe they are a bit better? the dimensions are fairly similar, the differences seem minor.... what would you think?
ps is lead spacing/thickness fairly similar in capacitors of the same size?
regards
vlad
I am thinking about going for a pair of these (see link below). they are exactly the same size as the original (3cm diameter, 5 cm high).
| 6800μF 63 V dc Aluminium Electrolytic Capacitor, 20% |
also these at the bottom have the same capacitance and voltage, but the dimensions are slightly different (35 mm diameter, 40 mm height).
LGU1J682MELC | 6800μF 63 V dc Aluminium Electrolytic Capacitor, 20%, GU Series | Nichicon
the brand seems a bit more famous, maybe they are a bit better? the dimensions are fairly similar, the differences seem minor.... what would you think?
ps is lead spacing/thickness fairly similar in capacitors of the same size?
regards
vlad
sure does, i do it all the time...
63 volt rating means that your rails are probably in the 45 to 55 volt range.
so that extra capacitance with not hurt, it can even be better...
so depending on what space is available in your chassis, you can upsize it a bit...
i will even look for a cap that is rated for 105*C...
can you psost the model number of your amp so we can have a closer look at the psu?
I can't comment on the Jackcon brand, but if it's sold by RS they're probably OK. For what it's worth, I've never been disappointed with Nichicon. As far as going with higher capacitance than original, as long as you don't go crazy, say up to twice the original value it should be alright. The risk with too large is stressing the rectifier diodes and/or possibly causing the power transformer to run hot.
Mike
Mike
Now then. It hums and the caps look swollen. First, is the swelling the end of the can? And are you looking at aluminum can or are you looking at a plastic cover held in place by the plastic sleeve around the cap? MANY caps bulge out the plastic disc covering the end. The plastic disc warps from heat in the unit, while the actual cap underneath is not bulging.
Since you expect to replace them anyway, slit the plastic sleeve to free the end disc cover. is the can bulged under there or not?
The amp hums, is it 60Hz or 120Hz? Oh, you are in Oz, so 50Hz? In that case is it 100Hz or 50Hz? Does the volume or other control affect the hum in ANY way at all? Or to be more direct, how much ripple is on your main rails? What we don't want to do is order up a bunch of caps and install them only to find the hum remains. I am not saying the caps are innocent, but we need to know for sure rather than assume.
Since you expect to replace them anyway, slit the plastic sleeve to free the end disc cover. is the can bulged under there or not?
The amp hums, is it 60Hz or 120Hz? Oh, you are in Oz, so 50Hz? In that case is it 100Hz or 50Hz? Does the volume or other control affect the hum in ANY way at all? Or to be more direct, how much ripple is on your main rails? What we don't want to do is order up a bunch of caps and install them only to find the hum remains. I am not saying the caps are innocent, but we need to know for sure rather than assume.
thanks guys.
power is 50 hz here in oz.
the cans are aluminium.
yes, volume control does affect the hum.
does this happen when caps wear out?
cheers
vlad
power is 50 hz here in oz.
the cans are aluminium.
yes, volume control does affect the hum.
does this happen when caps wear out?
cheers
vlad
Short answer is, maybe. 🙄
Do you get any hum with nothing connected to any of the inputs (i.e. only speakers physically connected) and volume turned down? If so, caps may be bad. If not, you might have a ground loop problem.
Mike
your main filter caps need replacing...
if hum still persists, then one or more of the small local caps need replacing...
if hum still persists, then one or more of the small local caps need replacing...
Better that you go for higher voltage capacitors since the existing ones have bulged. Possibility is that they are used at their limits and replacing with higher voltage rated will save them. Size has to be checked.
Gajanan Phadte
Gajanan Phadte
next standard higher voltage is 80 volts, no problewm using these either as long as it fits your board...
btw, if you are into repaiiring stuf, an esr meter can really help you a lot, it removes much of the guesswork....
btw, if you are into repaiiring stuf, an esr meter can really help you a lot, it removes much of the guesswork....
thanks guys.
if i turn the volume up, the hum gets stronger.
if i turn it down, it keeps a constant (very audible) level.
if i turn the volume down completely (to zero), it stops.
i bought two caps from the local parts shop.
they are rated 8000 uf, 80 volt. 85 degrees max temp.
brand is Suntan CD13.
i was going to order online initially, but i went past the shop and had a look.... hopefully they do the trick 🙂
ESR meter sounds interesting!
cheers!
if i turn the volume up, the hum gets stronger.
if i turn it down, it keeps a constant (very audible) level.
if i turn the volume down completely (to zero), it stops.
i bought two caps from the local parts shop.
they are rated 8000 uf, 80 volt. 85 degrees max temp.
brand is Suntan CD13.
i was going to order online initially, but i went past the shop and had a look.... hopefully they do the trick 🙂
ESR meter sounds interesting!
cheers!
measure the voltage across the main smoothing capacitors.
If it's less than 55Vdc (to allow for a rise when mains voltage is high) then buy 63V capacitors.
Don't waste your money on 80V capacitors.
Buying 105°C capacitors instead of 85°C capacitors may give a (slightly) longer life, or maybe not. Longer is the more likely, but it depends on a lot of factors.
If it's less than 55Vdc (to allow for a rise when mains voltage is high) then buy 63V capacitors.
Don't waste your money on 80V capacitors.
Buying 105°C capacitors instead of 85°C capacitors may give a (slightly) longer life, or maybe not. Longer is the more likely, but it depends on a lot of factors.
if you post the schem i can tell you which caps to check out...
you will need that ESR tester to check you caps....
Peak ESR70 capacitance meter is $100 plus $12 freight here. I can replace 200 little caps and 6 big ones for that. The ear says (before and after test) most of the caps I replace are marginal or bad. 40 years on e-caps, out they go in my book. Only 20 years, measure the max power out of the amp: an analog voltmeter is a lot cheaper than an ESR meter. You can measure AC ripple voltage on main cap at full power too, with a VOM. Analog VOM Useful on car battery/starter circuits, too. DVM produce random numbers on non-powerline frequencies (music), in my experience.
unfortunately I can't find a schematic for Sherwood RD 6405 on the internet... I wonder if any other model might be similar enough?
otherwise I could remove the case and take some pictures of the circuit board if that might help...... but in principle, I am going to start by replacing the two biggest electrolytic caps in there, which are located near the transformer.
seems like an ESR meter costs a bit.... if it's not crucial, and I can do without one, I would rather spend a bit less money, this time at least 🙂
just out of curiosity, how does volume indicate where the hum might come from? what connections are there between volume controls and whatever might cause hum?
thanks again guys 🙂
otherwise I could remove the case and take some pictures of the circuit board if that might help...... but in principle, I am going to start by replacing the two biggest electrolytic caps in there, which are located near the transformer.
seems like an ESR meter costs a bit.... if it's not crucial, and I can do without one, I would rather spend a bit less money, this time at least 🙂
just out of curiosity, how does volume indicate where the hum might come from? what connections are there between volume controls and whatever might cause hum?
thanks again guys 🙂
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