How to discharge Capacitor Can Filter

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JMPGuitars
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Re: How to discharge Capacitor Can Filter

Post by JMPGuitars »

PS. If you want to understand basic electricity stuff better, search on youtube for more details, or check out this page: https://www.allaboutcircuits.com/textbo ... urrent-ac/
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Re: How to discharge Capacitor Can Filter

Post by davemojo »

geoff 1965 wrote:
Fri 04/09/21 10:25 am
LeifH is right about "positive & negative" for mains AC so lets keep it simple,brown 230V "live" and blue 0V "neutral"
do you measure 230 volts at the brown wire at the mains socket,limiter socket and power input socket on the amp? remember your 230V into the transformer is the white wire.
regarding the 220K bleed resistor, "never" rely on that discharging "always" check for voltage at the caps with your multimeter before working on the amp!
Yes I am 100% about safety I agree I indeed check cap filter voltage using an alligator clip attached to ground and other end to black tip of multimeter set on DC voltage

With one hand in the pocket I probe with red tip of that multimeter to check on the positive to see if any voltages left :)
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Re: How to discharge Capacitor Can Filter

Post by davemojo »

JMPGuitars wrote:
Fri 04/09/21 10:39 am
I drew two diagrams for commonly used / switched dim bulb testers. If you're wired correctly, the test will tell you if you have a short. If you don't have a short, proceed with your next steps in the build/test process.

Thanks,
Josh

Dim Bulb Testers.pdf
Thanks this is exactly how I did it

I thought that when you switch on the amp with the stand by switch to off, the light should have glow bright for few secs but depending on the bulb light Watts this is not always true as per that video sent earlier
You do not have the required permissions to view the files attached to this post.
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Re: How to discharge Capacitor Can Filter

Post by JMPGuitars »

IIRC the amount of current limited is based on incandescent wattage. With incandescent bulbs, I think the wattage translates to percentage, but it's not the same with other bulb types. Try 100W, then try lower wattages. Using a switch on the tester itself probably makes any bright moments more obvious (mostly based on subtly and where your eyes are focused).

Thanks,
Josh
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Re: How to discharge Capacitor Can Filter

Post by LeifH »

davemojo wrote:
Fri 04/09/21 1:16 am
LeifH wrote:
Thu 04/08/21 9:44 pm
Ok, just a dumb electrician here...

1. the ground always has to be connected to the chassis. Remember you're dealing with fatal voltages.
2. Without the ground connected, if there is a short to ground, the limiter won't glow bright because the current has no place to go.

Make sure the ground is connected or your test is incomplete. Check everything first, remember to put on your safety glasses, put one hand in your pocket turn your face away before switching things on.

As a side note, with the AC coming from your wall plug or mains as you say, there isn't a positive or negative. Its AC, the electrons are going both ways.
Brown is line, in your case, 230v
Blue is neutral or common. 0V. (Think centre tap Ov on the output of your power transformer)
Ok I understand will set it up today again from scratch, with ground connected . I can't plug directly to wall receptacle, because it is far from my desk which is the place where I built the amp and have all my tools around. therefore I am using a lead extension with 8 sockets that has a switch and I am plugin the limiter in there and the Amp on the limiter.

However it is strange but the Amp light was lit, but if you are saying without ground can't be seen if there is a short, then I haven't done anything good.

What still puzzle me is that on previous reply what you put in series it matters I put the blue wire in series (neutral or negative) and the brown from the cord that goes into the socket outlet of the current limiter itself

Anyway let me figure all out again
Where you connect the lamp is important, in respect to both being safe and for the purpose of fault detection.

In your case it should be in series with the brown, line or hot, never the blue, common or neutral.

The simplest explanation is; if the lamp (current limiter) is in series on the line or hot (brown wire) the path the current takes is always through the lamp.

If the lamp limiter is in series with the common or neutral (blue wire) the path the current takes may not always be through the lamp. For example a fault to ground before or inside the power transformer.

I hope that clears up the why?
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Re: How to discharge Capacitor Can Filter

Post by davemojo »

LeifH wrote:
Fri 04/09/21 3:42 pm
davemojo wrote:
Fri 04/09/21 1:16 am
LeifH wrote:
Thu 04/08/21 9:44 pm
Ok, just a dumb electrician here...

1. the ground always has to be connected to the chassis. Remember you're dealing with fatal voltages.
2. Without the ground connected, if there is a short to ground, the limiter won't glow bright because the current has no place to go.

Make sure the ground is connected or your test is incomplete. Check everything first, remember to put on your safety glasses, put one hand in your pocket turn your face away before switching things on.

As a side note, with the AC coming from your wall plug or mains as you say, there isn't a positive or negative. Its AC, the electrons are going both ways.
Brown is line, in your case, 230v
Blue is neutral or common. 0V. (Think centre tap Ov on the output of your power transformer)
Ok I understand will set it up today again from scratch, with ground connected . I can't plug directly to wall receptacle, because it is far from my desk which is the place where I built the amp and have all my tools around. therefore I am using a lead extension with 8 sockets that has a switch and I am plugin the limiter in there and the Amp on the limiter.

However it is strange but the Amp light was lit, but if you are saying without ground can't be seen if there is a short, then I haven't done anything good.

What still puzzle me is that on previous reply what you put in series it matters I put the blue wire in series (neutral or negative) and the brown from the cord that goes into the socket outlet of the current limiter itself

Anyway let me figure all out again
Where you connect the lamp is important, in respect to both being safe and for the purpose of fault detection.

In your case it should be in series with the brown, line or hot, never the blue, common or neutral.

The simplest explanation is; if the lamp (current limiter) is in series on the line or hot (brown wire) the path the current takes is always through the lamp.

If the lamp limiter is in series with the common or neutral (blue wire) the path the current takes may not always be through the lamp. For example a fault to ground before or inside the power transformer.

I hope that clears up the why?
Yes but I have changed that as you and many other said, using the brown in series, then the ground and the blue straight to the outlet.

However the bulb light doesn't glow and the only reason why can be only because the amp doesn't draw enough power. The bulb light is 150 Watts

If I create a short on the receptacle the bulb light bright up so it works, that also means there is no short on the amp.

Anyway I will report back when is all ok and the guitar is plugged in and works as expected.
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Re: How to discharge Capacitor Can Filter

Post by davemojo »

Today I will add the tubes and make further test as per start procedure to see how it goes since I need to check if the tube sockets were all soldered properly.

So far step 1 turning on the amp did go well and step 2 turning on the stand by switch did go well too.

All I intended about the bulb limiter test was to have an answer if it was normal that the bulb wouldn't glow at all.

Unfortunately is my mistake since actually on the start up procedure is written

" If you are using a light bulb current limiter when you turn the power switch on the limiter light bulb will initially glow as the power transformer comes up to voltage and then dim because without the tubes in place no current is being used. If you are using a high wattage light bulb you may not even see the bulb glow. If the bulb burns near its rated brightness then there is a short in the power cord, power transformer or their connections."

Thanks all so far for the help received without i couldn't make it.
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Re: How to discharge Capacitor Can Filter

Post by geoff 1965 »

okay,i would double check you have the "live" 230V from the mains through the bulb to the white wire of the power transformer.test with the tubes in before plugging a guitar in,the point of the limiter is if there are any leakage/shorts it goes to the least point of resistance "i.e. the tungsten filament of the bulb" and not through the guitar to you!
one thing that threw me initially is on your layout the power on/off switch breaks the neutral 0V line,usually it's in series with the fuse but i've seen other schematics like yours
good luck and be safe
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Re: How to discharge Capacitor Can Filter

Post by crgfrench »

Sorry to chime in late, I haven’t logged in for a long time, hope everybody’s doing OK. To discharge caps you can just short them directly if you feel brave. You can use an alligator lead, or a wire, or a screwdriver, whatever. It might spark and make some noise. No worries. All that stuff about resistors is fine, but it’s just to give you a feeling of safety. Just short them to ground. That will drain them. Cesar Diaz did it all the time on the road, with just a screwdriver. See the 25:00 mark in this video https://youtu.be/-VHvQT-DPZ8
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Re: How to discharge Capacitor Can Filter

Post by Bieworm »

crgfrench wrote:
Mon 04/12/21 9:45 pm
Sorry to chime in late, I haven’t logged in for a long time, hope everybody’s doing OK. To discharge caps you can just short them directly if you feel brave. You can use an alligator lead, or a wire, or a screwdriver, whatever. It might spark and make some noise. No worries. All that stuff about resistors is fine, but it’s just to give you a feeling of safety. Just short them to ground. That will drain them. Cesar Diaz did it all the time on the road, with just a screwdriver. See the 25:00 mark in this video https://youtu.be/-VHvQT-DPZ8
Craig... admit it...you just like welding 😄😄😄
I do it too... laziness I guess
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Re: How to discharge Capacitor Can Filter

Post by JMPGuitars »

The screwdriver method is fairly common for small caps / lower voltages. I wouldn't do that on a guitar amp filter cap though. The feeling is safer with a insulated resistor, because it is safer. ;)
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