How to discharge Capacitor Can Filter

18watt-specific Tech Talk - Building, Fixing, Parts, Mods...

Moderators: CurtissRobin, colossal, zaphod_phil, Daviedawg, Graydon

User avatar
davemojo
Occasional poster
Occasional poster
Posts: 129
Joined: Wed 01/06/21 4:14 am
Location: Hoofddorp
Contact:

How to discharge Capacitor Can Filter

Post by davemojo »

Hi All,

As some of you know a few weeks ago I have finished the 18 Watts build.
To test if the work was done correctly I was told to follow the bulb light current limiter test.

I have built the bulb light current limiter as you suggested, with 150W bulb light 230v.

I was told to put a 220K 2 Watts resistors on the Filter Capacitor to bleed off the current from the filter.

Unfortunately forgot to get one of those resistors the only one I have is 220K .5W too little

So I know is possible to discharge Cap Filter using this see photo below, do I have to simply put the black tip onto either the negative or positive of the Cap Can and the red tip on the other end connection of that cap?
You do not have the required permissions to view the files attached to this post.
0 x
Davide Violante
Rockers&Rocks
www.rockers.rocks

User avatar
JMPGuitars
Super Duper Admin
Super Duper Admin
Posts: 2756
Joined: Tue 09/18/12 8:00 pm
Location: South Central, MA
Contact:

Re: How to discharge Capacitor Can Filter

Post by JMPGuitars »

Order some resistors!

Even if you want to make a discharge device, you still need the correct resistor. I have one I made using an old DMM probe. I added a 220K resistor inside the probe, clipped off the banana plug and added an alligator clip.

Never be lazy or impatient about safety. You can't use your amp if you're dead.

Thanks,
Josh
1 x
'I installed a skylight in my apartment yesterday... The people who live above me are furious.' - Steven Wright

Modern Ground Schemes
Soldering Technique
B+ Voltage Reduction


Web Design: DolceVittoria.com
Guitars / Amps / Effects: JMPGuitars.com
(anti)Social: Facebook · Instagram
Items for Sale

User avatar
davemojo
Occasional poster
Occasional poster
Posts: 129
Joined: Wed 01/06/21 4:14 am
Location: Hoofddorp
Contact:

Re: How to discharge Capacitor Can Filter

Post by davemojo »

Sure in fact I am not proceeding I want to live. :D

Regarding the start up procedure the first part they ask for in here is:

https://robrobinette.com/Tube_Amp_Startup.htm

On testing ground they are saying to:

Safety Ground
Before adding power to a new amp be sure and verify the safety ground connection. Plug a guitar cable into an input jack and check that you have continuity (meter "beep") between the guitar cable's sleeve (the part that isn't the tip) and the amp's power cord ground prong. In the USA it looks like this:



Verify you have continuity between the amp's power cord ground prong and guitar cable and speaker cable sleeve.

I verified all input jacks with guitar cable and multimeter and there is a continuity

I have order the specific 220K resistor 2 W already I'll wait
1 x
Davide Violante
Rockers&Rocks
www.rockers.rocks

Riffmonster
Newbie
Newbie
Posts: 83
Joined: Tue 02/09/16 12:38 pm

Re: How to discharge Capacitor Can Filter

Post by Riffmonster »

If you do not have a discharging tool, you can use your DMM to discharge a capacitor. It takes longer though.

Check here: https://www.youtube.com/watch?v=H3eyBGy2x1I
2 x

User avatar
davemojo
Occasional poster
Occasional poster
Posts: 129
Joined: Wed 01/06/21 4:14 am
Location: Hoofddorp
Contact:

Re: How to discharge Capacitor Can Filter

Post by davemojo »

JMPGuitars wrote:
Wed 04/07/21 6:02 am
Order some resistors!

Even if you want to make a discharge device, you still need the correct resistor. I have one I made using an old DMM probe. I added a 220K resistor inside the probe, clipped off the banana plug and added an alligator clip.

Never be lazy or impatient about safety. You can't use your amp if you're dead.

Thanks,
Josh
Hey Josh,

Hope you doing well, today I'll get the resistors 220K 2W metal oxide and place it on the filter cap between the positive and negative lug as shown on that schematic I have seen earlier, therefore if after the bulb light limiter test, there is no short, after unplugging the amp do I still have to check voltage on the filter cap?

I think is a good practice though!

Do I have to discharge capacitors on the turret board too?

After the first test with bulb limiter and everything shows ok, I believe I can add the tubes and retest again isn't?

Thanks
0 x
Davide Violante
Rockers&Rocks
www.rockers.rocks

User avatar
davemojo
Occasional poster
Occasional poster
Posts: 129
Joined: Wed 01/06/21 4:14 am
Location: Hoofddorp
Contact:

Re: How to discharge Capacitor Can Filter

Post by davemojo »

Posting the same on this one unsure which one I should use to get attention and some help

Here some results

I have connected the bulb light current limiter between the wall receptacle and the Amp.
I put the amp standby switch on and the amp main switch off.
I plugged the amp power cord into the bulb limiter and the bulb light limiter to the wall receptacle, it is actually a lead extension that goes into the wall.

I then at this point kept amp standby switch on and turned on the amp, the amp indicator light turns on but the bulb light didn't go on at all no even for a sec, so either I built the bulb light limiter wrong or something else isn't right. However the amp didn't smell any burned or smoked or anything like that.

The light on the amp was lit red but i switched all of after about 10 secs

The current seems to be flowing to the amp since the amp light is lit, unsure what's wrong with bulb limiter.

In the Netherlands the power cord cable are made with 2 colors brown and blue + ground yellow/green

On the limiter I didn't use any ground I have connected the brown cable from power cord plug to the bulb light holder took another piece of brown that goes from the other side of the connector straight to the outlet where the amp will be connected

The blue cable instead runs directly to the outlet and doesn't engage on the bulb light holder,

Hope my explanation is clear, see photo

Thanks
You do not have the required permissions to view the files attached to this post.
0 x
Davide Violante
Rockers&Rocks
www.rockers.rocks

geoff 1965
Frequent poster
Frequent poster
Posts: 906
Joined: Mon 01/04/16 3:52 pm

Re: How to discharge Capacitor Can Filter

Post by geoff 1965 »

which is positive & negative? in the UK brown is positive and blue is negative,the light bulb connections need to be in series with the "positive" mains on the limiter,your pic shows the blue in series,double check!
0 x

User avatar
davemojo
Occasional poster
Occasional poster
Posts: 129
Joined: Wed 01/06/21 4:14 am
Location: Hoofddorp
Contact:

Re: How to discharge Capacitor Can Filter

Post by davemojo »

geoff 1965 wrote:
Thu 04/08/21 8:39 am
which is positive & negative? in the UK brown is positive and blue is negative,the light bulb connections need to be in series with the "positive" mains on the limiter,your pic shows the blue in series,double check!
Thanks I think is the same here so I must do it the other way around damn it I used to leave in the UK and there I knew it that positive is the brown, but someone told me here was the opposite most likely he was wrong. Let me try again
0 x
Davide Violante
Rockers&Rocks
www.rockers.rocks

User avatar
davemojo
Occasional poster
Occasional poster
Posts: 129
Joined: Wed 01/06/21 4:14 am
Location: Hoofddorp
Contact:

Re: How to discharge Capacitor Can Filter

Post by davemojo »

Ok I have inverted the wire and connected the brown in series
I can confirm now that in the Netherlands brown is positive and blue negative

The blues goes straight off from the power cord into the bulb light outlet where the amp will be plugged in.
As stated instead the brown goes in to once side of the bulb light holder and the other brown is connected on the other side of the bulb light holder basically I have done the opposite of the picture shown earlier

Again the amp light lit, no bulb light glow, not even when the amp is switched on
0 x
Davide Violante
Rockers&Rocks
www.rockers.rocks

geoff 1965
Frequent poster
Frequent poster
Posts: 906
Joined: Mon 01/04/16 3:52 pm

Re: How to discharge Capacitor Can Filter

Post by geoff 1965 »

Which schematic did you use for the limiter? you need to have the ground connected for safety at the mains plug and socket of the limiter,double check you have brown “positive”at mains plug and limiter socket.
0 x

User avatar
davemojo
Occasional poster
Occasional poster
Posts: 129
Joined: Wed 01/06/21 4:14 am
Location: Hoofddorp
Contact:

Re: How to discharge Capacitor Can Filter

Post by davemojo »

geoff 1965 wrote:
Thu 04/08/21 1:02 pm
Which schematic did you use for the limiter? you need to have the ground connected for safety at the mains plug and socket of the limiter,double check you have brown “positive”at mains plug and limiter socket.
Yes ok but for the purpose of making this work and to absorb a potential short a ground is not absolutely needed if there is a short on the amp the bulb light will glow bright

https://www.youtube.com/watch?v=wRFRwOnLsZI&t=4s

This is what I have followed
0 x
Davide Violante
Rockers&Rocks
www.rockers.rocks

User avatar
davemojo
Occasional poster
Occasional poster
Posts: 129
Joined: Wed 01/06/21 4:14 am
Location: Hoofddorp
Contact:

Re: How to discharge Capacitor Can Filter

Post by davemojo »

So here my thoughts

I thing here the issue is that we don't really have a proper definition of polarized socket where you can define the brown as positive and blue negative

The problem is that i can connect the brown in series and that is my positive

But once i plug the power cord of the limiter into the extension lead how do I know really which side is the brown or the blue since i can turn the plug in both direction so...

I am getting confuse here in a normal situation blue or brown when connecting a lamp with wiring it doesn't really matter the light lights up
0 x
Davide Violante
Rockers&Rocks
www.rockers.rocks

geoff 1965
Frequent poster
Frequent poster
Posts: 906
Joined: Mon 01/04/16 3:52 pm

Re: How to discharge Capacitor Can Filter

Post by geoff 1965 »

the link you followed has the ground connected at mains & limiter socket,the way you have it wired at the moment when you plug the amplifier in it has no chassis ground connection!
yes you need to determine which is positive & negative at the mains socket,then you can check your wiring is in series and not crossed.
be careful
1 x

User avatar
LeifH
Unrated
Posts: 23
Joined: Tue 10/06/09 2:00 am
Location: Unknown

Re: How to discharge Capacitor Can Filter

Post by LeifH »

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)
1 x

User avatar
davemojo
Occasional poster
Occasional poster
Posts: 129
Joined: Wed 01/06/21 4:14 am
Location: Hoofddorp
Contact:

Re: How to discharge Capacitor Can Filter

Post by davemojo »

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
0 x
Davide Violante
Rockers&Rocks
www.rockers.rocks

Post Reply