# Help! electrolytic capacitor 5000 MFD needed

D

#### DB

Jan 1, 1970
0
Looking for a replacement for a blown Mallory electrolytic capacitor for a
power supply. The capacitor has three terminals, 2 red and one black. The
capacitor label has the following notation:

Mallory
5000 MFD 20 VDC RED
5000 MFD 20 VDC RED
25002 235-7244A

I did a Google search and could not find anything similar. I am wondering
if anyone has any idea where I could find a suitable replacement.

The capacitor is part of an EICO Battery ELiminator and Charger, Model
1064S.

Any assistance would be greatly appreciated.

- D. Boucher

D

#### DB

Jan 1, 1970
0
Unfortunately I don't have a schematic. There is only one capacitor, but it
has three terminals. That and the notation on the side makes me think it
may be some kind of a dual capacitor in one big can. I had never heard of
such a thing before, but could that be what it is?

- D. Boucher

D

#### Daniel

Jan 1, 1970
0
DB said:
Unfortunately I don't have a schematic. There is only one capacitor, but it
has three terminals. That and the notation on the side makes me think it
may be some kind of a dual capacitor in one big can. I had never heard of
such a thing before, but could that be what it is?

- D. Boucher

John Fields said:
---
Unless you need an exact replacement for esthetic reasons, any
modern aluminum electrolytic capacitor rated for 20V or more should
work.

If the capacitors are used singly you'll need to get something like
two, 5100µF 20V caps or of they're wired in parallel, a single
10000µF 20V cap should work. Check Digi-Key or Mouser, they're sure
to have something you can use.

Do you have a schematic you can post?

Two capacitors, that share a single negative terminal, in the one
package. Cannot say I've seen it before but sounds reasonable.

Failing a schematic, can you try following the actual circuit to give us
an idea?

Is it possible that the wires off the capacitor red leads go to the
cathodes of two diodes who's anode then connect to windings on a
transformer with the capacitors negative terminal going to another
transformer terminal?

Daniel
*** Encrypt your Internet usage with a free VPN account from http://www.SecureIX.com ***

A

#### Al

Jan 1, 1970
0
Daniel said:
DB said:
Unfortunately I don't have a schematic. There is only one capacitor, but it
has three terminals. That and the notation on the side makes me think it
may be some kind of a dual capacitor in one big can. I had never heard of
such a thing before, but could that be what it is?

- D. Boucher

Two capacitors, that share a single negative terminal, in the one
package. Cannot say I've seen it before but sounds reasonable.

Failing a schematic, can you try following the actual circuit to give us
an idea?

Is it possible that the wires off the capacitor red leads go to the
cathodes of two diodes who's anode then connect to windings on a
transformer with the capacitors negative terminal going to another
transformer terminal?

Daniel
*** Encrypt your Internet usage with a free VPN account from
http://www.SecureIX.com ***

I guess you guys never worked with toob circutis. Multiple capacitors in
one can with one negative are quite common. But not in the values you
show. I'm looking at one right now:

22-3457 F
10 Mfd 400V
4 Mfd 350V
4 Mfd 150V
20 Mfd 50V

Date Code, ta dah, 6149

cans apart carefully and replaced the internal capacitors. You would
never know from the outside.

Al

A

#### Alexander

Jan 1, 1970
0
John Fields said:
---

More than likely, that's precisely what it is. Back in the stony
ages it was quite common to have two or three electrolytics in the
same can. The way you describe yours though, makes it sound like
there's a separate terminal coming out of the base for the common
connection, when usually a tab which was part of the case was used
for the common connection. Is thare any other marking on the case?
Like "TYPE FP" or anything like that?

The reason I ask is because there are lots of people selling Mallory
capacitors on the web, and if you know the type number you should be
able to use Goggle to find a source.

Failing that, If you took the thing apart to find out what's
_really_ in the can, as Al suggested, you could substitute what's in
there with new caps or, if you wanted to get really fancy, put the
new caps in the old can for a tidy repair. Caps today are so much
smaller than they were back then they'd prob'ly fit right in there.

I remember a VCR I disposed of 'bout a year ago.
This one had a nice cap with 4 terminals in it this part and other
parts were defect.
btw. the VCR was a Video 2000 (one of the first of them).
I never fancied opening Capacitors, even those descriped, because
sometimes you immediatly get the electrolyt out of the case.
Sometimes the opening happens by accident

Alexander

D

#### DB

Jan 1, 1970
0
John Fields said:
---

More than likely, that's precisely what it is. Back in the stony
ages it was quite common to have two or three electrolytics in the
same can. The way you describe yours though, makes it sound like
there's a separate terminal coming out of the base for the common
connection, when usually a tab which was part of the case was used
for the common connection. Is thare any other marking on the case?
Like "TYPE FP" or anything like that?

The reason I ask is because there are lots of people selling Mallory
capacitors on the web, and if you know the type number you should be
able to use Goggle to find a source.

Failing that, If you took the thing apart to find out what's
_really_ in the can, as Al suggested, you could substitute what's in
there with new caps or, if you wanted to get really fancy, put the
new caps in the old can for a tidy repair. Caps today are so much
smaller than they were back then they'd prob'ly fit right in there.

I opened the power supply up and traced the wires. The black terminal is
connected directly to the negative output terminal. One of the red
terminals is connected directly to the positive output terminal. The other
red terminal is also connected to the positive output, but through a large
coil with an iron core. The second red terminal is also connected to a DPDT
switch that selects the output range and through that to a diode array and a
variable transformer.

There are no markings on the capacitor other than what I indicated in my
first post.

I'll try the thing of putting new caps in the old can -- it would certainly
make it easier to mount them.

- DB

A

#### Al

Jan 1, 1970
0
"DB" <[email protected]> said:
I opened the power supply up and traced the wires. The black terminal is
connected directly to the negative output terminal. One of the red
terminals is connected directly to the positive output terminal. The other
red terminal is also connected to the positive output, but through a large
coil with an iron core. The second red terminal is also connected to a DPDT
switch that selects the output range and through that to a diode array and a
variable transformer.

There are no markings on the capacitor other than what I indicated in my
first post.

I'll try the thing of putting new caps in the old can -- it would certainly
make it easier to mount them.

- DB

Looks like what you have is a pi filter. Leading cap., choke, trailing
cap. Values of the caps are important in this schema.

Al

J

#### James Thompson

Jan 1, 1970
0
Looks like what you have is a pi filter. Leading cap., choke, trailing
cap. Values of the caps are important in this schema.

Al

db, are you for sure that the caps are bad?
What was the problem that lead you to diagnose the caps?

leaking or exploded? I have changed caps before , but its not that often
a main power supply filter dies. Tell us what the unit was doing...

D

#### DB

Jan 1, 1970
0
James Thompson said:
db, are you for sure that the caps are bad?
What was the problem that lead you to diagnose the caps?

leaking or exploded? I have changed caps before , but its not that
often a main power supply filter dies. Tell us what the unit was doing...

One minute the Power supply was working fine, then it vibrated for a split
second and then the fuse blew. I replaced the fuse, and the same thing
happened again when I turned it on. I opened the power supply up and I saw
that there was some dried yellow crusty material that appeared to have oozed
out of the capacitor near one of the terminals. It looked like it had been
that way for a while, but I had just recently started using this power
supply after it had been sitting on a shelf for about 12 years.

I checked the resistance between the capacitor terminals (without removing
the capacitor from the circuit), and found that there was no resistance. I
don't know if that is normal.

- D. Boucher

D

#### DB

Jan 1, 1970
0
John Fields said:
More than likely, that's precisely what it is. Back in the stony
ages it was quite common to have two or three electrolytics in the
same can. The way you describe yours though, makes it sound like
there's a separate terminal coming out of the base for the common
connection, when usually a tab which was part of the case was used
for the common connection. Is thare any other marking on the case?
Like "TYPE FP" or anything like that?

I picked up a couple of 5000 MFD 25VDC capacitors for $1 each, hoping that they might be suitable replacements. The new capacitors are marked "Type PFP." The old 5000 MFD 20VDC dual capacitor didn't have any markings to indicate the type. The old capacitor case looks like it is made of bakelite, by the way. The new capacitors have three terminals that are part of the aluminum case, and a fourth terminal slightly off-center from the base. The fourth terminal has a little square marking next to it. There does not appear to be any measureable resistance between any of the terminals, including the central one. I am wondering how I can determine if these capacitors are suitable replacements. I'm also not sure how to figure out which terminal should be connected to the positive output of the power supply, and which to the negative. Any assistance would be greatly appreciated. - D. Boucher D #### Daniel Jan 1, 1970 0 DB said: One minute the Power supply was working fine, then it vibrated for a split second and then the fuse blew. I replaced the fuse, and the same thing happened again when I turned it on. I opened the power supply up and I saw that there was some dried yellow crusty material that appeared to have oozed out of the capacitor near one of the terminals. It looked like it had been that way for a while, but I had just recently started using this power supply after it had been sitting on a shelf for about 12 years. I checked the resistance between the capacitor terminals (without removing the capacitor from the circuit), and found that there was no resistance. I don't know if that is normal. - D. Boucher Just to be clear, do you mean that you ohm-meter showed there was zero ohms between the terminals or did it show there was no connection (i.e. an open circuit) between the terminals? Daniel *** Free account sponsored by SecureIX.com *** *** Encrypt your Internet usage with a free VPN account from http://www.SecureIX.com *** D #### Daniel Jan 1, 1970 0 John said: --- The capacitor you have is one of the Mallory PFP types which is a twist-lock capacitor for PCB mounting. Twist-lock because usually the tabs on the case were slipped through slots in the PCB (type PFP) or through the chassis (type FP), and then the tabs were twisted with a pair of pliers to lock the capacitor down. The case is almost certainly negative, leaving the center pin positive. The reason you're measuring zero resistance between the center pin and the case is because they're pretty good size capacitors and it'll take a good while for them to charge up with the current from your ohmmeter. If the capacitors are discharged at the start, when connecting the ohm-meter there should be maximum current flow, indicating zero ohms, for an instant, then, as the capacitor charges, the amount of current will decrease until, in the end, the capacitor is charged to the same voltage as the ohm-meter is providing, so indicates zero current flow, or as an open circuit, i.e. infinite resistance. Depending on the internal resistance of the ohm-meter, this could take almost zero time or substantial time Daniel Also, if they haven't been used in some time the oxide on the plates might not be in the best condition, so what you might want to do is put an ammeter in series with the cap and measure the current going into it while it's charging from a low voltage. When you first connect it the ammmeter will show a _LOT_ of current, but as time goes by you should see the current drop and eventually settle on a very low value. When it gets stable, increase the voltage and watch the current until it gets stable again. Do that until the voltage across the capacitor is at 25V, and then just let it sit there with power on it for a few hours. If everything is OK the ammeter should read only a few milliamperes after a few hours. BTW, what kind of test equipment do you have access to? *** Free account sponsored by SecureIX.com *** *** Encrypt your Internet usage with a free VPN account from http://www.SecureIX.com *** D #### DB Jan 1, 1970 0 Daniel said: If the capacitors are discharged at the start, when connecting the ohm-meter there should be maximum current flow, indicating zero ohms, for an instant, then, as the capacitor charges, the amount of current will decrease until, in the end, the capacitor is charged to the same voltage as the ohm-meter is providing, so indicates zero current flow, or as an open circuit, i.e. infinite resistance. Depending on the internal resistance of the ohm-meter, this could take almost zero time or substantial time Daniel Also, if they haven't been used in some time the The only test equipment I have is a$9.99 multi-meter from Harbor Freight.
The PFP capacitors have never been used, and appear to be brand new. The
ohmmeter reading is zero ohms across all terminals, for both the new and old
capacitors.

I tried connecting one of the new caps in series with a flashlight battery
and measuring the current. The current slowly but steadily declined. I did
the same thing with each side of the old dual capacitor, and in each case
there was a quick spike in current, followed by a steady current of approx.
0.9 mA.

- D. Boucher

D

#### Daniel

Jan 1, 1970
0
John said:
---
Most of my multimeters, on the 200 ohm full scale range, supply
about 1A into a short, so if we consider the ohmmeter a constant
current source it'll take:

dv C 1V * 5E-3F
t = ------ = ------------ = 5 seconds
I 1e-3A

to charge the cap up to a volt through the ohmmeter. Not exactly
what I'd call "almost zero time"

All fine and dandy if the Ohm-meter were a constant current source and
the capacitor could just keep absorbing those electrons, but neither is
the case so your logic fails.

(As a side note, I'll give you 5E-3F is the same as 5000 microfarads,
but 1e-3A is not the one amp you say your multimeter can supply into a
short. If you fix this in the workings, t = 5 milli-seconds, which I
would call "almost zero time" when talking about digital multi-meter
response time.)
But, to be fair, I put a Fluke 8060A on the 200 ohm range across a
4700µF 35V cap and it only had time to give me one reading before it
went "OL". OTOH, on the megohm range it took it 10s to get to
0.0020, so if the OP's using a cheap 3-1/2 digit meter on the high
resistance range, he may have seen 0.000 and not given it a chance
to rise any higher before disconnecting.

Daniel
*** Encrypt your Internet usage with a free VPN account from http://www.SecureIX.com ***

J

#### James Thompson

Jan 1, 1970
0
One minute the Power supply was working fine, then it vibrated for a split
second and then the fuse blew. I replaced the fuse, and the same thing
happened again when I turned it on. I opened the power supply up and I
saw that there was some dried yellow crusty material that appeared to have
oozed out of the capacitor near one of the terminals. It looked like it
had been that way for a while, but I had just recently started using this
power supply after it had been sitting on a shelf for about 12 years.

I checked the resistance between the capacitor terminals (without removing
the capacitor from the circuit), and found that there was no resistance.
I don't know if that is normal.

- D. Boucher
Most likely the crusty yellow stuff is glue and the cap is good.
Caps are sometimes glued in during the assembly. The way you said it went
out ( power supply) , if it were the
cap going bad, you would find paper all over the inside (it would explode).
I would lood for a diode ( bridge or single ) , or a transistor shorted.
Use you ohm meter to check for a near
zero resistance on one of them.
Let us know what you find..

Replies
13
Views
1K
Replies
5
Views
2K
D
Replies
0
Views
1K
D
Replies
6
Views
1K
Replies
3
Views
35