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Are Your Capacitors Installed Backwards? Build this and find out

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This content explains the importance of correctly orienting polarized capacitors in vintage audio equipment and provides instructions for building a test jig to identify the "outside foil" or shielded end of these capacitors, crucial for minimizing hum and interference.

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hi there if you're into restoring old

receivers or old radios and restoring

old guitar amplifiers or even building

amplifiers you probably find this

information rather interesting so those

orange dip Brown dip Green Dip and those

little yellow axial leaded capacitors

and many more capacitors have a polarity

in circuit and should be installed in

the circuit the correct way in order for

them not to pick up hum from adjacent

parts of your amplifier or radio or to

pick up interference from adjacent parts

of the chassis whatever they're

installed into so in this video what

we're going to do is we're going to

discuss why these capacitors have a

polarity and then we're going to build a

little circuit that will help us locate

this polarity quickly we all know that

if you're restoring an old radio or an

old guitar amplifier they usually have a

handful of capacitors in them and you

really don't want to be doing this while

you're restoring the receiver or

amplifier so we're going to build a

little circuit that'll help you grade

them with an oscilloscope very quickly

and then you with a little felt marker

you can mark the band end or as it was

called in the old days the outside foil

end of the capacitor so let's get into

the video and start discussing why these

capacitors actually have a

polarity here we have two very common

circuits that you'll find in a lot of

vacuum tube gear this upper circuit here

you'll notice is in a lot of guitar

amplifiers or High Fidelity amplifiers

or stereo receivers this really is just

an an audio amplification ation chain

here this bottom portion of the

schematic I've kind of drawn to

represent either an if amplifier or an

audio amplifier of course we'd have to

amend this Transformer to represent

either or but we're not going to get too

crazy about that right now because it's

all about just learning which way we

need to install our new capacitors in

this circuit for the best circuit

performance and the least amount of

interference so way back in the day they

used to make capacitors that looked like

this and if you ever find a capacitor

like this

in any kind of gear that you're working

on it has to go uh these are all faulty

by now and they leak now when I talk

about leaking I don't mean that they

leak physically they're not leaking a

substance like oil or goop out of them

they leak DC across them so whenever you

hear the term leaky capacitor that means

that they're leaking direct current

through them capacitors are supposed to

block DC and pass alternating current

through them so when they leak that

means that this capacitor is a

effectively turning into a resistor and

that is no good for the next stage so

what happens in these capacitors is

they've got paper inside of them that's

gone acidic and it's basically just

turning into a big resistor right now

and when these capacitors turn into

resistors they bias up the next stage

and cause the tube over here to draw

heavy current it causes damage to the

Circuit you burnout plate resistors and

if Transformers and it does all sorts of

bad things so you want to get rid of

these capacitors and replace them with a

modern equivalent like a um an orange

dip or a brown dip and I'll grab one of

those here in just a minute to show you

so back in the day when these were brand

new they're great capacitors they didn't

leak or anything and uh they were nice

enough to Mark the outside foil end of

the capacitor by putting a band on it

and printing outside foil on it now the

outside foil end means that this lead on

the capacitor comes into here and it

also attaches to an outside foil jacket

that's just right underneath this paper

here and it Shields the entire capacitor

so if we were to tie this to the chassis

this whole capacitor would be shielded

right up to this point right to where

this lead goes in this lead goes it to

the inside layers so in effect these

capacitors actually do have a polarity

now so do a lot of the modern capacitors

and if they're built correctly they'll

actually be made with you know Metalized

polypropylene or uh you know PVC or

whatever they're building their new

capacitors with and of course whichever

new style capacitor that you end up buying

buying

they will have an outside foil jacket

connected to one end it's just that they

didn't spend the time to actually mark

it and that's what we're going to do in

this video is we're going to locate that

outer uh outer foil or the outer

Metalized polypropylene layer so that

when you install your capacitors into

circuit you're going to pick up less hum

and a less uh adjacent interference and

um you know there you're not going to

get oscillation because you have a

really large exposed surface hooked to a

high impedance portion of your your

circuit so now these capacitors we'll

just use this as an example for a modern

capacitor so say this was a a brand new

modern capacitor okay if we were to

install this into the circuit this end

here would go to the lower impedance

Point always so this end here with the

with a band if we were to use this as an

RF bypassing capacitor would always go

to the Chassy and this would go to the

the grid of the tube say the screen grid

if we wanted to keep RF off the screen

grid or something like that it would go

like this because when we tie this end

the chassis this entire capacitor is

shielded right up to this point now if

we hook this up in reverse and say we

tied this end of the chassis and this

end of the tube socket we'd have all of

this area that is completely exposed

right up to this point so of course we

don't want to have that because that's

more exposed area and of course we're

going to pick up more interference that

way especially if we have a a filament

or a heater Line running past this

that's that's definitely no good we

definitely want this end to the chassis

side now when we're hooking this up to a

standard audio amplification circuit

here this capacitor would go in this way

because the band end or the outside foil

end always goes to the lower impedance

portion of the circuit and the lower

impedance portion of the circuit most of

the time is the plate of the preceding

stage here or the earlier stage I should

say so this band end will always go

towards the plate and this end always

goes towards the Grid in this particular

circuit and in this capacitor would be

the same way and if we had a capacitor

on the input here it would be the exact

same way

again on this bottom circuit here we'll

notice that there is a capacitor missing

on the screen grid and this would be

considered an RF bypass capacitor we

want to keep RF off the screen grid here

because we don't want this screen grid

to amplify any kind of oscillations or

any kind of interference that's in the

chassis so by mounting this capacitor in

we would have to mount the band end to

the ground or the chassis and that would

tie to the screen grid now of course we

don't want a lot of lead inductance

there so we want to keep the lead as

short as possible but again you have to

use some common sense you don't want an

extremely short lead so that when you're

soldering it if you have a newer

capacitor you're going to melt the poly

uh the Metalized polypropylene with the

heat of your soldering iron you'll

probably need to leave a little bit of

lead so that it'll dissipate some heat

so again these capacitors need to go in

like this and they need to go in like

this and they need to go in like this

okay so depending on uh what stage or

what U what kind of schematic you've got

going on so now we have new capacitors

that look like this right here you can

see this this has no markings on it and

when these capacitors are created

they're going down the assembly line

this way and then they get the the

writing or the printing on them this way

or they'll get them on this way because

it really doesn't matter they're in a

machine that doesn't really pick pick

which way they go down the line so uh

they could be any old way and we need to

find out which end which lead is

attached to the outermost Metalized

polypropylene or we could call it the

the actual shielding inside the

capacitor which would be the outer the

outer layer the outermost layer of this

capacitor and that's very important so

that we install this into the circuit

the correct way cuz we don't know now a

lot of people think that when they buy

these orange dip Capac

that oh look they've been really nice

and they've marked that well really have

they this is how you test for the

outside shielded end of your capacitor

or the outside foil end or outside

Metalized polypropylene layer however

you want to call it we're really just

looking for the shielded end of your

capacitor and this is how you find it

using an oscilloscope and a very simple

little setup like this which is

basically just a BNC cable with a center

conductor attached to an alligator clip

and the Shi is also attached to an

alligator clip I have them right now

just clipped together to keep the noise

off the

screen so if you have a newer modern DSO

that goes down to about 5 molts per

division you should be absolutely fine

uh right now this is running at 2 molts

per Division and uh you know we're not

going to get too accurate with the

readings because really I'm just acting

as a random hum antenna in order to uh

to determine the outside foil end of

these capacitors and I'll explain that

here quite shortly so the first

capacitor we're going to look at is this

old wax capacitor now we wouldn't want

to use this in circuit because this

capacitor is well past its due date but

we're really just looking at a shielding

aspect of this capacitor so this will be

just fine for this test so what I'm

going to do is I'll hook this into

circuit the correct way and we'll look

at the signal on the screen in the

amplitude here and then we'll reverse

this capacitor and see the

differences so right now I'm just

connecting this thing up and this is the

way that it should normally be I'm

acting as the hum antenna right now I'm

uh holding the the case of the capacitor

right now so you could look at me as a

very nearby uh heater Line running past

this capacitor in in a chassis or

something like

that so that's the amplitude that we got

with it hooked up the correct way you

can see the banded end is connected to

the outside Shield of the cable this is

the lower impedance portion of the

circuit this would be the chassis and

we're always looking for the lowest

amplitude when we have found the lowest

amplitude we have the capacitor hooked

up the the correct way when the

amplitude is high it's hooked up

backwards so what I'll do is I'll hook

way and we can tell that we have this

hooked up backwards because now the

outside foil which is the the shielding

on this capacitor is capacitively

coupling to me and I'm feeding signal

into my oscilloscope so that we can see

here very simply that this capacitor is

now hooked up backwards remember we're

always looking for the lowest amplitude

and then we know when the negative or

the common lead of our oscilloscope is

hooked to that end when we have the

lowest amplitude that is the end that we

will Mark as the outside shielded end or

the outside foil end or whatever you

want to call it so that's this capacitor

here so let's grab a newer orange dip

capacitor and take a look at it so

here's a newer orange dip capacitor and

we have a line here and we might think

that oh that line indicates the outside

foil end well let's test that out I'll

just hook the capacitor up to it right

now it's much easier to hook this up off

of screen here so there we go so now

I've got this outside uh Shield of my

braid hooked up to this end this would

be considered the chassis and this here

would be considered the part that goes

into the high higher impedance portion

of the circuit okay so now what I'll do

is I'll flip these leads around now if I

flip these leads around and the

amplitude goes down that means that this

side is not the outside foil end

remember the side that the shielding is

on is always when the amplitude is lower

is the outside foil end so what I'll do

now and look at that we have lower

amplitude here so this line here does

not denote the outside foil end this

side here is the shielded end of this capacitor

so again I'll hook this back into

circuit the other way and we can see

that we have more amplitude this

around you can see that there's almost

nothing there so this side here would be

the side that we would want to connect

to the chassis we would mark this side

here with a line as the outside

foil okay so let's grab another orange

dip capacitor right here and test it out

the same way so I'll hook this up the

way that we would think that it's hooked

up this is the band end here so we'd

figure that that is the outside foil all

right so now what I'll do is I'll

leads and we can clearly see with this

capacitor that this side here is

definitely not the outside foil or the

outside Metalized polypropylene or

whatever Metalized PVC this here this

side is so this here would be considered

the shielded end of the capacitor this

is the side that would attach to the

this and you can very clearly see that

end so let's test an older capacitor

here here I have an older kind of a

burgundy dip I don't know what you would

call this but let's uh consider the line

end on this one as the outside foil so

now okay so here we

go all right you see the line is on this

end and we have the common or the

negative lead hooked up here all right

and we can see on this capacitor that

line does denote the outside shielded

end of the

capacitor so on this capacitor you could

regard this line as correct now whether

these capacitors are going down the run

like this and they're going down the run

like this we don't really know cuz I

don't have more of these to test but it

just so happens on this capacitor that

this end here is the shielded

end okay so let's take a look at this

old General instruments capacitor all

right and let's test it out and see if

this band end is the outside foil so

I'll hook this one up the way we would

think it would be hooked up

properly again we have the band end

hooked to the ground or the common this

would be considered the chassis

it and we can clearly see that this is

not the outside foil end on this

capacitor either so really the bands on

the ends really can be considered either

way with a lot of these capacitors so

really you need to test them in order to

really know what side is the outside

foil and you can very very clearly see

capacitors so I'll grab one of my my

brown dip ones

here all right and I'll hold this one

this one has absolutely no markings on

it so we'll test this one out here you

can see this one

leads it's just shorting there we got

these leads all twisted up there we go

so we can clearly see that this end here

is the band end right here even though

there are no markings on this capacitor

so you can see the differences there

there's the lower amplitude this way and

leads and we can see that we have higher

way so this end here is the shielded

end so now what we want to do is since

we're going to be testing these things

you know we're going to you know if

you're replacing a whole lot of these

things in a radio you're going to be you

know basically have a small bag full of

these things so you don't want to be

doing this as you're you know putting

these things in the radio you kind of

want to pre-grade these things and find

out which end really is the band end so

that you do install these things

correctly to short these leads out here

so um so what we're going to do is

create a small circuit that does this a

little bit easier for us and um we'll

check out maybe uh a couple of different

ideas and see what we can uh design here

and make a little uh make a little test

jig for these

things before I start building a small

project I usually like to check my own

stock and see if I have enough parts and

pieces to make this with the with the

parts that I have on

hand so I would like to build this into

a smaller Project Box and it just so

happens that I have another one around I

built the TDR out of the same one I

can't find the other Project Box I put

it in a very safe place so that uh I

would find it the next time as I can uh

as I can now see so anyways I'll locate

this other Project Box it looks just

like this one here except of course

there's nothing in it it's just a solid

you know uh cast box here so I'll end up

using this box here and the reason I

want to use this box over a plastic box

is this is completely shielded you got

to remember we have an oscilloscope

that's down at about 5 molts per

Division and maybe even 1 molt per

division so if we have a plastic box a

lot of noise is going to get into there

from anything that's basically around it

the thing is uh any kind of wire length

inside this box if it was plastic would

act as an antenna and we'd be picking up

all sorts of just noise and random

garbage so what we want to do is we want

to have everything enclosed in a solid

uh a cast box

here another thing that we have to think

about is you know a battery so I'm going

to need to install a battery in here and

I'm most likely going to end up using a

9volt battery for this so you know it's

going to take up a small portion of this

box so I have to locate things inside of

this project box so that you know this

whole thing will work out you know I

need to put a BNC Jack on here you know

I need to put a switch on it somewhere

the battery will have to be mounted in

here there'll have to be a small circuit

board in here that uh you know all of

our parts and pieces are going to be on

and we also have to think if we're going

to say I'm going to have two alligator

clips sticking out of the top of this

box or something like that all right now

I'm going to also have to have an LED

beside each alligator clip so that I

know when this thing is moving around

like this when it's reversing the

polarity of the capacitor so that we can

note the you know the amplitude

difference on the screen we're going to

have to have something that's going to

Mark the side that's the band end so I'm

going to have to have maybe some rubber

grommets and then you know maybe some

LEDs on the top of the box so everything

has to be taken into account because we

can't you know push the battery down on

top of the LEDs and we also need uh

space for the um for the wires to come

out of the top of the box so the battery

will have to sit over to one side and

this is all stuff that you have to think

about before you plan this so what you

do is of course you get your box and you

know you you put the battery inside and

you move things around and you know uh

you Pond over some things for a little

while and then when you you know come to

uh thinking okay you know this layout is

going to work then of course you can

start building with that layout so now

in order for this to make testing easier

we obviously need some form of a circuit

that's going to take this uh you know

capacitor and it's going to reverse it

and of course we don't want any imposed

noise from the circuit that it's around

so in order to make a circuit that's

going to reverse this we're going to

this so we can look at this as right

here if we were to have the capacitor

under test right

here so this is the capacitor under test

okay and say uh this here is the uh the scope

scope

common and uh this is the scope you know

the the center conductor we'll just put

plus here for just for uh ease of of

drawing okay so this is the center

conductor of the oscilloscope probe and

this here is the scope uh probe common

so if we want to have this in the

circuit say this is the negative side of

the capacitor here we're going to need

to close this switch and we're going to

need to close this switch in order for

the positive probe of our oscilloscope

or the Center conductor of the cable to

be attached to this side of the

capacitor which then would make this

this side here and then of course this

would run to ground so you can see we

have a circuit here now so then in order

to reverse this capacitor in order to

flip it these two switches would have to

open and then this switch and this

switch would have to close and then of

course that would make this side running

up to the uh to the center conductor

here and then this side here would end

up becoming the common side because this

would which is connected to ground and

we're going to also need some form of uh

say an LED or something at this point to

denote when this side here is the the

common side or whether this side here is

going to be the common side so we're

going to also need two LEDs to do that

so now we can do this with relays and of

course we're going to have a little bit

of current consumption if we do that

we're going to hear click click click

click inside this box or we can do this

with an IC and I'll probably end up

using an IC because there's uh you know

limited Uh current draw with an IC we

you know there's a bunch of ic's that

that basically work as um uh single pole

single throw

switches and you know I'll find

something that's rather common to use

and uh we'll make this particular

circuit using a bunch of ic's now if we

use an IC and it's got a bunch of fats

inside it we're going to also want to

have something on you know this

particular Point here which basically is

you know two diod like this one diode

like this and one diode like this and

that's going to also limit this

basically to about6 or 7 of a volt on

each side so just say there's a bit of a

charge on that capacitor say you forgot

to discharge it a little bit or if

there's you know you have a static

you're not going to zap this IC if we

use an IC so this is basically just

going to protect it and limit the

voltage that goes into the circuit now

of course you would always make sure

every single capacitor is discharged

before you stick it in into circuit and

all this is going to do is protect the

IC that these switches are in and of

course we would want the same thing on

this particular side here and uh it

would be exactly like this so basically

all that's doing is this is limiting

this uh input circuit where our

capacitor under test is to about 7 of a

volt now keep in mind that we're testing

most of this down at around oh know 10

you know maybe uh you know with our

amplitude maybe we're exceeding 50 60 70

molts with the hum in our and that we're

imposing into this capacitor who knows

but this is going to be up around 6 or

700 Mills just about a volt so um you

know this is uh well beyond our our uh

our test so this is just protecting this

here so now what we're going to also

need to do is we're going to need to

implement some sort of a circuit that's

going to close these two and close these

two and then it's going to have to do

this right in order to flip this

capacitor back and forth and back and

forth so we're going to need some sort

of a flip flop probably a dtype flip

flop or something like that and then uh

if this is an in an IC these are going

to be controlled so this side here right

and this side here would go to one leg

of the flip-flop and then this side here

and of course this side here would go to

another part of the FP flip-flop now

keep in mind that this is just only a

rough sketch and I'm just trying to get

the idea across when it comes to

actually designing this we'll go over to

the White board and uh take a look at it

there so now that we have a flip-flop

that's basically just going back and

forth like this you know once this when

this side is positive say um you know

we're going to probably not use a um

just a

74hc we'll probably use a CD 74hc ic's

for this because we're dealing with a

9volt battery uh just 74hc logic is

usually only good to between about 5 and

7 volts maximum so we're going to be

using a 9vt battery so we're going to be

wanting to use uh uh parts that start

with CD and of course we'll take a look

at the data sheet just to make sure that

uh you know it will be fine around the

9vt area so now that we have this this

uh this type flip-flop here now we need

also a timer that's going to set out a

pulse into this that's going to tell

this to go back and forth like this so

of course when this side is high this

side is low right and then when this

side is high this side is low so

basically what this is going to do is

it's just going to close these two

switches and then close these two

switches and then close these two so you

know when these two are closed these are

open obviously and it's just going to go

back and forth like this and we also

want to set the timing rate of this

timer so that when we have this thing on

the bench and we're looking at say our

oscilloscope here we want it to go slow

enough so that when we can see the

amplitude change on our oscilloscope the

amplitude goes down and then the

amplitude goes up we want to have a

chance when it goes down again to look

at the box and note which led on which

side of the box is going to be lit up so

when we know that you know the amplitude

is low and this led is lit up we'll know

that this side here would be the band

end of the capacitor so that's what we

want to try and do so these are the

parameters that we're basically dealing

with we have a 9volt battery so we know

that we're going to need like U you know

a CD 74hc parts or just CD Parts uh the

555 timer is good for 9 volts so we

don't really have to worry about that

we'll use a 555 over here probably a d

flip-flop or something like that and uh

I'll have to figure out some really

common part for this so that way uh you

know it's easy to to put together now if

you have a bigger box you don't need to

use a small box like I'm doing you can

build this onto that um you know that

protoboard stuff and you can use through

whole ic's I'll probably end up building

this for myself with surface mount stuff

just so that I can fit it right inside

this box and then you know this box will

have a b and c come off of it and then a

power switch and it'll probably have two

little alligator clips now now the the

cables that are going to come out of

this box I want to be shielded right up

to the alligator clips because uh you

know if we have just two long wire

sticking out of here those are really

two acting as two antennas so the more

shielding we can get right up to the

alligator clips the better so I'll have

two small shielded pieces of coax coming

up here and of course we want you know a

little bit of lead length so we can move

them around if we have you know a large

axial capacitor we can clip them onto

the ends or if we have one of the uh the

newer style ones I'll grab this one here

we have one of the newer style ones like

this you know we can just you know put

the two leads together and clip them in

like this so the whole idea is to make

this thing functional especially if

you're going through all sorts of

different types of capacitors you know

we want this thing to be about just as

versatile as we can make it so now that

we have the plan here I'll figure out a

an actual circuit and I'll draw it up

and we'll head on over to the Whiteboard

and I'll explain it

there this is the circuit I've designed

for our little capacitor test jig so I

ended up using a CD 74hc

4066 to flip the capacitor around in

circuit now this is an IC and it's a CD

74hc 466 it's not just a 74hc 4066 and

the reason that I used this one is that

it will go up to 10 volts remember that

we need to keep the supply voltage of

our ic's well within a safe zone I'm

using a 9volt battery over here to power

this and again this is all just due to

size constraints uh I have that little

aluminum box or that little cast box

that I showed showed you that I'm going

to end up fitting this all in uh if it's

around here somewhere I still haven't

found it but uh I'll fit all that into

that box uh again you know you can build

this into any kind of size box if you

have a larger aluminum box you can uh

you know of course uh use a different

kind of battery style power source for

this you know a bunch of able a

batteries or whatever fits in that box

just keep in mind that the box has to be

either solid metal or solid aluminum or

a cast box some sort of conductive box

because uh again our oscilloscope is

running down you know between 1 and 5 Ms

that's going to pick up any kind of

noise uh no power supplies running into

this thing at all it should be battery

powered so we'll get back to the Circuit

I've drawn this IC the same way that you

would kind of look at relays just to

make it a little bit easier to

understand so how this IC works is

really quite simple it really is just

four switches inside of one IC so pin 13

pin 5 Pin 12 and pin 6 are the control

pins so if say pin 13 goes High that'll

connect pin two and pin one so

technically it just closes a switch

inside so pin 13 and pin 6 are tied

together pin 12 and pin 3 are tied

together so basically it's just closing

the switches like this and this is all

done within an IC there's very low

current consumption you don't get the

clicking from a relay and uh you know

it's a it's a real consistent test

because we're using fets inside this in

order to switch this in circuit now

there will be a little bit of uh

resistance in the switch and I'll

explain that in a little bit it's

between 15 and 20 ohms but that's

absolutely fine for testing these Capac

capacitors there'll be no issues with

this whatsoever so this was a really

good solution the cd74 84066 is a really

common part it's an off-the-shelf part

you should be able to find that with no

problems again you can build this

through hole you don't need to build

this surface mount the only reason I'm

building this surface mount is because

in my little box it's uh it's hiding

here somewhere and I'll I'll I'll put

all the stuff inside that little box so

uh these are

bav99 uh these are just uh they're two

diodes in one so23 package uh you don't

need to use the bav99 you can use a 1n

4152 or a 1n 914 or if you think you're

going to be crazy and leave a capacitor

charge and stuff it into the circuit you

can use a one in 47s or whatever you

want to use remember this is just

working at a really low frequency is you

know you're you're coupling the 60 Cycle

uh signal in from your body really and

uh you know just you know inducing Helm

into the circuit so that you can see

which end is the shielded end so really

not too picky so I use the bav99 9 just

because they fit on the little circuit

board quite nicely so and I'll uh I'll

get into this here in a little bit I've

already got the little circuit board

already pre-drawn and and ready to go

and we'll get into that next I'll show

you how I've drawn that up so that's one

of the reasons that I use these they

just they fit on there really quite

nicely so now here I've got a CD 4013

which is a flip-flop it's a d style

flip-flop and what that what this really

does is when it receives a puls in pin

11 of this IC what it does is it just

basically this pin will go high this

will go low and then it'll receive

another pulse and it turns the other way

and it just keeps going back and forth

like this now you can see I've got two

really high brightness LEDs here and the

reason that they're high brightness is

because I I'm using a 22k to ground

resistor and you can use one or two it

really doesn't matter uh the reason I'm

using this is because they pull very

very low current and they're still

pretty bright at that point so I don't

want to use up my battery power like

LEDs you got to remember in the circuit

One LED will always be on it's just

going back and forth so when this side

here goes high this led will glow now

this led here should be positioned by

the negative part of the switch so pin 8

and pin 9 where pin uh pin 4 and pin 8

run out to your alligator clip that's

where this led should be located all

right so where this led should be

located should be close to pin 1 and pin

11 so what's going to happen is is when

this side goes High it closes this

switch and that what that's doing is

that's bringing this side of the

capacitor to ground and we we're

remember that we're looking for the

negative side of the capacitor or the

shielded side of the capacitor and you

want this led close to this side you

want the red LED close to this side so

when this side goes high this one here

is pulling this side of the capacitor to

ground again we're looking for the

shielded side of the capacitor if you

have the LEDs reversed you'll end up

marking the wrong side of your capacitor

and I'll show you how to test for that

in the end to make sure that you have

the LED on the Right End just in case

that's a little bit

confusing again the we have a a pulse

going into pin 11 here so again this is

just going like this and you can see the

action with the LEDs the LED you'll see

the LEDs move back and forth this is a

555 timer and what this little 555 timer

is doing is just creating the pulses in

order to tell this flip-flop to do its

flip flopping so it's just going to keep

it doing this now I've chose a 180k

resistor and a 1K resistor because I

find that to be a very nice balance you

don't want this to go too fast because

you're not going to be able to look at

the screen and then you know really

quickly look down to the box and then

see which LED's lit and mark the line on

it right you want enough time so that

you know when you see the the amplitude

goes small you can look at the Box see

which LED's lit and draw a line on and

then by that time it's already back over

to the other side again and I'll explain

all this in the end and you'll see how

this actually functions so so you can

speed this up if you want if you find

that this is a little bit too slow and

uh you know you want to be Superman as

you're you know uh grading all your

capacitors and you're you're just

hammering them through really quick you

can change this 180k resistor down to

150k and it's going to go quicker 120k

and you're really working all right uh

if you find that 180k is too fast up to

220 and you'll have plenty of time to to

sit there and and have a sleep between

the LEDs as they're switching back and

forth okay so this 180k resistor you can

put a VR in there again I'm keeping it

simple I'm I'm dealing with size

constraint because of that little box

that I've got so uh I just want this

thing basically you turn on a switch and

the thing just starts doing its action

and I can grade cap so it's just a happy

medium so 180k and 1K work very well I'm

using a 22 mic tanum capacitor down here

and the reason I'm using a 22 mic tanum

capacitor is because I have a lot of

them so that's really the only reason um

there's a 01 cap coming off of five just

to keep noise out of the 55 5 um you'll

see here that these are all the supply

lines for all the icc's we have pin 14

and pin 14 pin 7 and pin 7even for both

of these ic's and 48 and 1 for the 555

so uh 14 14 4 and 8 are all positive so

4 and8 and this is pin 14 and there's a

pin 14 on this that also has to be tied

to positive and we have pin seven pin

seven and pin one so there's a pin 7even

on this IC that has to go to ground

there is a pin 7even on this IC as we

can see here that goes to ground and

then we have pin one here going to

ground and that's really just the supply

again you can put the switch in the

positive or the negative side absolutely

fine whatever you think uh will work

just fine for you so I've got a 22 M cap

on the supply here just to uh to keep

noise out of the circuit when this thing is

switching uh what else can I tell you

here uh I think that's pretty much it uh

this will draw between 3 to 8 milliamps

somewhere in there depending on the ic's

and the manufacturer and everything um

that's really quite nice if you use

relays you're going to end up with uh

quite a bit more current consumption so

that was the whole idea of uh of using a

9volt battery and a bunch of ic's we can

you know we'll get a really long life

out of this um out of this little switch

so everything should work just fine

scope common goes to pin uh 10 and pin 9

so basically pin 9 and pin 10 of the

4066 will just tie to the chassis or to

the box and then the BNC Center that you

have coming uh right that goes right out

into your scope will tie rate to pin two

and pin three so uh and then of course

that's that's you know a continual and

then you you know this isn't moving this

is your scope hot your and your scope

calm and there's nothing moving there

that's that stays there and then of

course the switching is going to do its

switching at that point inside the IC

and flip that capacitor around as this

uh 555 timer is telling this flip-flop

to go back and forth and uh that's

pretty much it so uh what I'll do is

I'll take you over to the computer now

and I'll show you the little um a layout

that I've got designed up and it's a

surface mount layout again you don't

have to do it surface mount you can

build it through hole or however you

want to build this you can build it dead

bug style u whatever works for you so

let's head on over to the

computer this is the surface mount

version circuit board that I've come up

with for this little capacitor

tester so this is really quite blown up

this is a really small circuit board but

uh I've just enhanced it so that it's

easier to see on camera here so this is

uh the top layer the Green Layer is the

the top and the black is the back side

of the circuit board so this is a

double-sided circuit board this little

IC here is the 555 timer this is pin one

this is the timing cap that 22

microfarad tanum here these are 0402

Parts this is the 180k resistor this is

the 1K resistor and this is the 01

microfarad capacitor off pin five this

here is the other 22 microfarad tanum

that's across the supply this here is the

the

cd4013 which is the uh the flip-flop and

this is the

4066 over here the cd74 HC 4066 this is

what's going to be doing our switching

here these here are the screws where it

mounts to the chassis of uh that little

aluminum or a cast box that I've got

these are the resistors that's on the

back side this resistor is a 22k

resistor and this is the LED this led

correlates to this side this is the test

lead that runs out this side this is the

center conductor and I will solder The

Shield or the braid of that little piece

of coax to this piece of the circuit

board here and then of course we want

the LED close to that rubber grommet

where the uh where the test lead runs

out and it's the same for this side this

is where the center conductor of our

test lead runs up to the alligator clip

The Shield of the coax will solder to

here and this led correlates with this

side so these are the high brightness

LEDs here these are 126 Parts here these

are two 22k resistors uh this is where

the supply 9vt Supply runs in right here

and this is where the BNC signal runs

out this goes to the BNC Jack on the box

and it goes out to our oscilloscope from

this little Point here and that's really

how this works so this is really quite

small and I'll show you exactly how this

is going to go together here in the next

shot here is the completed little

capacitor testing box here we can see

that I've got my alligator clips

fastened to some shielded coax this is

some Teflon coax here this building runs

up to about this point here and about

this point here you don't need to use

teflon coax you can use any kind of coax

you want I just have a bunch of this

stuff around I've put some heat shrink

on the ends here just to stiffen things

up where the the center conductor Runs

Out to the alligator clip because you

know we're going to be moving this

around and moving it in and out of

circuit quite a bit and I want to get

some longevity out of this without

having the connections break now of

course nothing sticks to Teflon very

well so uh I've left a little bit of

braid exposed and this heat shrink here

has a little bit of glue inside of it so

it sticks to the braid quite nicely and

uh we see the corresponding LED for this

wire here and the corresponding LED for

this wire here when this led is lit this

one here is tied to ground and when this

led is lit this side here is tied to

ground so we know which end to Mark our

band on these are two little rubber

grommets here that I've put in this is

the BNC Jack here that will run out to

the oscilloscope and there's a bunch of

screws here that just hold the circuit

board in and this is the on andof switch

on the side

so on the bottom half you can see here

I've got a little 9vt battery stuck in

there and there's a little piece of be

tape that's just holding it in uh this

is the circuit board that I've built and

this is the little switch in the

negative lead I'll just zoom into this

here so we can take a little closer look

stuff so you can see the ic's here

that's the little 555 timer that's the

4066 down in there and that's the 4013

flip-flop and that's the uh the little

tanel capacitor the timing cap and so on

and so forth just like on the layout

those are all the little 0402 parts

right down there the 180k the 1K and the

the 01 mic

capacitor uh you can see how I've

soldered the braid of the coax right to

the circuit board here and then the

center conductor runs up to this little

spot this little sot23 package part here

is that bav99 diod that's just

protection so I don't zap the IC in

there it's the same on this end I

soldered them in sideways because if I

ever need to replace them they be pretty

easy to get out this way and put back in

again you can use a 1 and 47 or a 914 or

anything like that you know it's a again

we're you know we're dealing with a 60

Cycle frequency here so there's nothing

that needs to be too incredibly fast let

see what else can I tell you those are

the LEDs that are soldered in you'll see

that there's a space between the circuit

board here and the actual case and

that's because there's Parts on the back

side of the circuit board and there's

also uh soldering on there so when I put

the uh the bottom portion of the box

together here I had to cut this out on

the corner here and on this corner

because the circuit board goes you know

very close to the corner here and

they've got this kind of extruded lip

that runs all the way around the entire

box here so there's enough space between

the back side of the circuit board and

the case to leave this strip in here it

just goes between the circuit board and

the case you can see here here's the

circuit board that will go right in between

between

here and that's pretty much the Box so

when we turn the thing on this is about

the speed that it runs at with the um

with the 180k resistor

here you can see how fast that moves

back and

forth so that gives us enough time to

Mark our capacitor and um you know of

course look at the screen and and you

know load a new capacitor I think that's

about a nice comfortable speed for

grading these capacitors so next let's

hook this thing up to an oscilloscope

and see how it

works we're ready to check the clar ity

of some capacitors in our test

jig so I've got the oscilloscope set to

5 molts per division I've got the

alligator clip shorted here and I'll

plug this in and I'll show you that it's

a relatively quiet

circuit you can see how quiet that is

right now now you got to keep in mind

that through this IC when this side is

grounded it's about 17 ohms to ground

and then when this side is on it 17 ohms

to ground so we have 2 17 or around that

ohm paths one from positive and one to

ground and that's just the uh basically

the resistance imposed by the IC itself

so even though we still have this you

know we're going to still pick up noise

from the oscilloscope if we bring it

close to it and everything but you know

for this actual test this is absolutely

fine and for this little test jig it's

it's fine so when we open these

alligator clips we're going to see lots

of noise on the screen and that's

absolutely normal because these are

acting as antennas and this is actually

just picking up noise from the scope

itself even you can see the amount of

noise that comes in from the

CRT so when we put the capacitor in here

under test it actually acts as a filter

across the circuit itself so there is no

problem with the amount of noise that we

see so what we'll do now is we'll put a

capacitor in here let's take this orange

dip capacitor and test it out and mark

the band

end so here we have me being the 60

Cycle antenna

again and you can see the difference in

amplitude here

as it's switching so we see this led is

on and the amplitude is lower so this is

the band

end you see so now that we see this led

on we would mark this end as the band

remember we're always looking for the lowest

amplitude so I'll take my felt marker

and I'll put a little line on this end

and I'll know that that now would be the

lower impedance portion of the the

circuit this would go to the chassis or

this side would go to the plate side if

we have this in an

amplifier again we can see that this

side has a band on it but we can see

that it doesn't really mean anything you

know according to the outside shielding

or anything this might be some sort of

coating that they've put on or I don't

know what they're doing and why they've

put this on this one end but um this

side here you know clearly denotes the

outside foil or the outside Metalized

polypropylene or Metalized PVC layer

okay so there's one so we've marked this

one and you can see the speed is

comfortable so that you know it's you

know you're not losing control of what

you're doing so I'll put this one

here all right so we know that this end

also okay so I'll mark this as the band

end now if you don't want to leave your

felt marker on there you know you can

use an ink that will easily come off uh

I find that you know a little bit of

alcohol will just remove these lines

even if it is one of these Sharpies so

uh uh you know a lot of people don't

want that line on the capacitor when

it's in circuit um i' I've kind of

leared to live with it I I kind of like

to have the uh the capacitors clean

myself but um that's fine for underneath

the chassis I I'm now just beginning to

leave the lines on like you will end up

seeing in most of my videos so this one

here this side here the this opposite

side here this one on this side is the

band end where I've drawn that little

one so we can see that the opposite end

on this capacitor is the band end so

this end is the band end on this

capacitor so you can see there really is

no Rhyme or Reason for these capacitors

you know they're just kind of going down

the line any old way they're the same

capacitor and they're just printing the

uh the uh the labeling on any side there

so it really is important to mark that

off let's test out this one here and

end okay is that in the shot there it is

here okay so this end is the band end

right here so now we would mark this end

as the band end and that's just how

simple it is to grade and check your

capacitors so you know that you're

putting them in circuit the correct way

and that's how this little fixture works

so what we're going to end up doing next

is I'll show you how to measure which

end is actually supposed to be the uh

the negative end so that you have your

LEDs corresponding to the correct lead

just in case you did find that a little

bit confused

confusing all right this is how we tell

how we've got the right LED on the right

lead so this is the lead here that we're

going to test and we want to know if

this led is corresponding to this

connecting to ground so we've got our

our meter on ohms and we have our lead

going into the alligator clip here and

you can see that it's 17 ohms when this

led comes on see that so we know that

this end is connecting to ground and we

have our polarity right

right so what I'll do now is I'll move

this over to this side and you'll see

roughly the same measurement on this

lamp all right it's me trying to get a

go so that's how you tell so if you wire

your LEDs up and you have them backwards

if you leave some lead length you can

just swap them around if you don't build

a circuit board or something like that

and that's how you tell that you've got

side well we've come to the end of

another video I hope you find this

little circuit useful and I hope you

enjoyed the video if you did give it a

big thumbs up and hang around I'll try

to make more videos just like this in

the very near future take care bye for

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YouTube Transcript:Are Your Capacitors Installed Backwards? Build this and find out