| ROVSING |
Could anyone explain the difference?
I've allmost finished my first GC, but when i "stripped" an old taperecorder the other day i found that ther were 1 cap on the ac-inlet seriel on each rail instead of one parallel, is this just another solution or is it even a better solution ?
Or is it something special fore taperecorders ?
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| digi01 |
| what you mean is a EMC filter? |
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| ROVSING |
Yes that is what i mean, on f.ex. on my BZLS preamp i've mounted a cap with one leg on AC hot and one leg on AC 0 as a filter, i will do that on my gainclone too, but if the filter gets even better by mounting 1 cap on each wire i will prefere that, the problem is that my technical knowledge in electronics are very small i'm better at working with steel, wood and design, but i am trying to learn by doing.
This is probably a small problem, but i am not able to see the difference, and if you don't ask you won't get any answers.....:confused: |
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| phn |
You mean like this?
I know even less than you about electronics, so this post is as much about "self-help." |
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| ROVSING |
| no more like this... |
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| pinkmouse |
| Hmm, mounted in series with the mains like that they are unlikely to be caps, maybe some sort of surge protection? Any chance of a picture? |
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| phn |
Man, was I way off.:D
Hopefully I will have learnt more by the time I get around to my own GC. |
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| boholm |
I have only seen capacitors in series in electronics that does not require much power - just like your tape recorder.
Unless there were some diodes there too? And how big are the capacitors? |
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| ROVSING |
| I will take a picture when i get home and then mail it tomorrow they are Rifa capacitors from a Technics taperecorder but i don't remember the values. I think it was something like 0.001 uF / 250v. |
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| runebivrin |
A capacitor in series with the AC inlet blocks any DC component from saturating the transformer, which can be useful to stop the transformer from humming, getting warm and using inordinate amounts of current. One or two makes no difference, unless they're electrolytic and connected with opposite polarity.
There's usually a couple of diodes across the caps, to protect in case the caps go bad.
Rune |
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| ROVSING |
| Thanks for the explanation RUNEBIVRIN i think i got it now, here is the picture anyway....;) |
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| steenoe |
| quote: | | A capacitor in series with the AC inlet |
A question: Won't that limit the current draw capability, in case
this is implemented in a poweramp? In this case a GC.
The usual way is to place a X2 rated cap in parallel with the
AC lines. BUT, that doesn't really kill the DC residual on the AC line though! See pic for the usual way to do it. The trafo on the pic still suffers from a mechanical noise. The red component in the middle at the rear is a X2 rated Wima MKP, 0,1uF.
What we need is an easy to implement solution that takes care of the DC. Hopefully some of you guys can come with right one
for this problem. Perhaps, what is really needed is something like this?http://www.lcaudio.dk/index.php?page=12
Go down to "DC filter stop brummet" There you see a schematic.
Couldn't find the filter on the page in english, sorry.
Steen. |
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| runebivrin |
| quote: | Originally posted by steenoe
A question: Won't that limit the current draw capability, in case
this is implemented in a poweramp?
Steen. |
Well, that depends on the size (in µF) of the capacitors. There won't be much voltage across it, so you can have rather large caps. As an example, 10 amps at 230 volts represents an impedance of 23 ohms. If you want the caps to have little impact, let's say you want 0.23 ohms impedance. That means the capacitors need to result in 14000µF, or 28000 if you have two in series. That's a lot, but you'll only need 16V types (albeit large ripple current types.)
Scale according to power requirements, mains frequency and voltage.
Rune |
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| steenoe |
| quote: | | Well, that depends on the size (in µF) of the capacitors. There won't be much voltage across it, so you can have rather large caps. As an example, 10 amps at 230 volts represents an impedance of 23 ohms. If you want the caps to have little impact, let's say you want 0.23 ohms impedance. That means the capacitors need to result in 14000µF, or 28000 if you have two in series. That's a lot, but you'll only need 16V types (albeit large ripple current types.) |
I am sorry, but do not exaktly understand!
Please clarify if you can! Are you talking about the X2 caps?
That would be an impossible value:xeye: Normally rated about 0,1uF????? Or are you referring to the LC schematic?
I still feel that this would be a great thing for DIY'ers to solve??
Steen. |
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| leadbelly |
| quote: | Originally posted by runebivrin
That's a lot, but you'll only need 16V types (albeit large ripple current types.) |
That's unsafe practice. Everything on the mains side must be specifically mains rated and identified as such. |
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| runebivrin |
| quote: | Originally posted by steenoe
I am sorry, but do not exaktly understand!
Please clarify if you can! Are you talking about the X2 caps?
That would be an impossible value:xeye: Normally rated about 0,1uF????? Or are you referring to the LC schematic?
I still feel that this would be a great thing for DIY'ers to solve??
Steen. |
By placing capacitors in series with the transformer primary, you'll prevent any DC component from entering it. It's not about having a capacitor parallel with the transformer. See attached pic.
| quote: | Originally posted by leadbelly
That's unsafe practice. Everything on the mains side must be specifically mains rated and identified as such. |
I can't comment on the legal issues, but from a technical standpoint that's ludicrous. I know for a fact that none of the light blubs in my christmas tree lights are rated at 230 volts.
See this for an example: URL=http://www.soundlabsgroup.com.au/lcaudio/lc_audio_mains_dcfilter.htm]LC Audio DC filter[/URL]
Rune |
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| leadbelly |
| quote: | Originally posted by runebivrin
I can't comment on the legal issues, but from a technical standpoint that's ludicrous. I know for a fact that none of the light blubs in my christmas tree lights are rated at 230 volts.
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Apples and oranges. (1) Your Christmas tree lights have been IEC stamped somehow or you could not have bought them, so the assembly has been certified as a whole. Similarly that LC Labs product has likely gone through some process. (2) I never said that just putting a capacitor rated at 230V was what was required or even sufficient. The capacitor must be mains certified and labelled as such specifically. It must say something like 180VAC or 250VAC. Look in your electronics catalog for examples. |
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| ErikdeBest |
Maybe that cap was installed in parallel with the power switch. I think that it helps to prevent great inrush current, giving the switch a longer life...but a cassete recorder has no great power consumption. Well...don't know :S
(I took the drawing from a schematic from triodedick) www.triodedick.com |
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| runebivrin |
| quote: | Originally posted by leadbelly
Apples and oranges. (1) Your Christmas tree lights have been IEC stamped somehow or you could not have bought them, so the assembly has been certified as a whole. Similarly that LC Labs product has likely gone through some process. (2) I never said that just putting a capacitor rated at 230V was what was required or even sufficient. The capacitor must be mains certified and labelled as such specifically. It must say something like 180VAC or 250VAC. Look in your electronics catalog for examples. |
And I said "I can't comment on the legal issues", but nevertheless, there is no indication in LC Audio's product that the cap is anything but a bog standard electrolythic capacitor at 22000µF/25V. It may be approved by some authority, but it doesn't say.
It's particularly interesting that the cap will be reverse polarized, albeit at a low voltage.
Are you suggesting that every component in a comupter power supply - which switches the rectified mains voltage - are somehow "mains rated"? Every single resistor?
The bulbs in my christmas light are not specifically certified for use in mains powered equipment, but I will grant you that the sockets most likely are, since they will have 230VAC across the contacts with a broken bulb.
Rune |
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| runebivrin |
| quote: | Originally posted by ErikdeBest
Maybe that cap was installed in parallel with the power switch. I think that it helps to prevent great inrush current, giving the switch a longer life...but a cassete recorder has no great power consumption. Well...don't know :S
(I took the drawing from a schematic from triodedick) www.triodedick.com |
That cap is useful, but not for inrush current, but for preventing voltage spikes on switch-off creating sparks that would shorten the life of the contact surfaces.
Different caps for different purposes!
Rune |
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| pinkmouse |
| quote: | Originally posted by runebivrin
Are you suggesting that every component in a comupter power supply - which switches the rectified mains voltage - are somehow "mains rated"? Every single resistor? |
If it has mains voltage across it, then yes, or it wouldn't get it's CE ,(or UL in the States), rating.
As for your Christmas lights, if you went out to a reputable dealer today, I bet you wouldn't find anything but low volt versions... |
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| runebivrin |
| quote: | Originally posted by pinkmouse
If it has mains voltage across it, then yes, or it wouldn't get it's CE ,(or UL in the States), rating. |
Well, that's really the point, isn't it. The cap in the DC filter we're discussing doesn't have mains voltage across it. The LC Audio version will suffer at most 4.3 volts. My schematic only goes to 0.7 volts, so a 25 volt cap will be quite safe.
| quote: | Originally posted by pinkmouse
As for your Christmas lights, if you went out to a reputable dealer today, I bet you wouldn't find anything but low volt versions... |
Not so, not in Sweden at least. Almost every houshold has at least one electric candle holder with 7*34 volt 3 watt incandescent lights that plug directly into the wall socket. Thousands are sold every year. Christmas trees will have light chains with 18 14 volt bulbs (or was it the other way around - hm, christmas stuff neatly packed now). Sure, you can get stuff with LEDs, but that isn't nearly as cosy.
Rune |
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| pinkmouse |
| I see no CE mark on that circuit pcb...;) |
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| Peter Scowcroft |
Jumping back to christmas lights there.
It is a common (and too frequently fatal) mistake to assume christmas lights are low voltage.
One of the bulbs was shattered in my setup this christmas. without unplugging it i ripped out the bulb (with now exposed metal contacts) and plugged in the new one.
A few seconds later two neurones connected and i realised my lights did not have a transformer!
:eek:
Then again i have rewired a broken electrical lamp before.
Halfway through i felt a funny tingle in my hand. suddendly my megahungover brain realised the light was in the mains and turned on.
The "tingle" was electrisity passing through my hands!
Long story short electricity kills...though not when you are hungover. |
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| runebivrin |
| quote: | Originally posted by pinkmouse
I see no CE mark on that circuit pcb...;) |
Agreed - you don't. I'm not quite certain, but I think the laws concerning electrical safety in Europe are different that what one might suppose - and what used to be. From what I gather you're pretty much allowed to manufacture and sell anything. If it causes injury or material damage and it's not CE certified you're in deep trouble. CE certification is something anyone can slap onto their product, but if in fact the product doesn't meet certification standards you're in even bigger trouble. If it is CE certified, meets the standards but somehow causes injury or damage anyway that's too bad, but accidents will happen.
In short: You as a manufacturer vouch for its adherence to CE standards, but it's wise to have it tested by a certified lab. It's up to consumers to look for the CE mark.
Back in the good, old days, before Sweden joined the EU, it was mandatory to have any mains powered electrical device tested and certified by SEMKO (the Swedish Electrical Material Checkup Organization). It could the be stamped with a ringed S, which was compulsory for devices sold to consumers. SEMKO still does a lot of the CE certification tests. Expensive but rigorous, and the S mark is still well recognized as a sign of electrical safety in Sweden.
Rune |
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| runebivrin |
| quote: | Originally posted by Peter Scowcroft
Jumping back to christmas lights there.
It is a common (and too frequently fatal) mistake to assume christmas lights are low voltage.
One of the bulbs was shattered in my setup this christmas. without unplugging it i ripped out the bulb (with now exposed metal contacts) and plugged in the new one.
A few seconds later two neurones connected and i realised my lights did not have a transformer!
:eek:
Then again i have rewired a broken electrical lamp before.
Halfway through i felt a funny tingle in my hand. suddendly my megahungover brain realised the light was in the mains and turned on.
The "tingle" was electrisity passing through my hands!
Long story short electricity kills...though not when you are hungover. |
Back in my younger days I worked a few years servicing consumer electronics. We had a contract to do service on the school gear in our town, which meant that every summer we tended to countless Tandberg reel-to-reel tape recorders. My "favourite" foul-up was to plug the thing in, test it superficially and then unscrew the chassis to look at the innards. At which point I routinely took a firm grip with my right hand across the mains switch. ZAP! We had full isolation transformers, and nothing really bad ever happened, but every time I swore it was the last time. I still get zapped once or twice a year, but I keep one hande in the pocket, so it just gives me the jitters.
Live and learn? Or maybe learn and live!
Rune |
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| pinkmouse |
Yes, that's very much how I understand the rules as well.
As for the christmas lights, a couple of years ago I had to get 1000 sets for an event. Mains voltage would have been perfect as we could have just spliced them into big ring mains. However, even dealing with the importers direct, I could only get LV in the UK, which was a real pain as it involved about twice as much work running sockets everywhere... |
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