Hello,

I have a circuit board that has a blown Fuse. The Fuse is a very
small SMD device that is mounted to the board. The device is a color
green if that matters with a capital "B" on the surface.

This is just a curiosity question for my own edification and
maybe for the benefit others.

Is there some chart that would be available to give the ability
to ID the value of this fuse and its parameters??

Then my other comment has a different tone.

Personally I think fuses of this design are a PITA. Yes, it is
smaller and makes for a "clean look" but when one might have been
blown by a possible spike on the line voltage in order to save the
rest of the board then the WHOLE board need to be replaced.

So then what is the point other than making more money.

If it seems that I might sound a bit frazzed, that would be correct.

I just don't understand the designing of this technology type
especially at a input voltage of 120VAC.

I am sure I will be enlightened to the whys and wherefores.
I am prepared for the best and worst.

Thank you very much in advance.

Les

ABLE1 wrote:

I have a circuit board that has a blown Fuse.Â* The Fuse is a very
small SMD device that is mounted to the board.Â* The device is a color
green if that matters with a capital "B" on the surface.

B probably indicates 125mA

check the size "1206" (3 x 1.5mm)

http://www.farnell.com/datasheets/1796765.pdf

On 10/31/2020 12:33 PM, KenW wrote:
Because they are cheap and can be wave soldered and last but not least
screw the buyer.


KenW


KenW,

Well that is a very honest response.

Thank You!!


Les

On Sat, 31 Oct 2020 12:26:25 -0400, ABLE1
wrote:

Hello,

I have a circuit board that has a blown Fuse. The Fuse is a very
small SMD device that is mounted to the board. The device is a color
green if that matters with a capital "B" on the surface.

This is just a curiosity question for my own edification and
maybe for the benefit others.

Is there some chart that would be available to give the ability
to ID the value of this fuse and its parameters??

Then my other comment has a different tone.

Personally I think fuses of this design are a PITA. Yes, it is
smaller and makes for a "clean look" but when one might have been
blown by a possible spike on the line voltage in order to save the
rest of the board then the WHOLE board need to be replaced.

So then what is the point other than making more money.

If it seems that I might sound a bit frazzed, that would be correct.

I just don't understand the designing of this technology type
especially at a input voltage of 120VAC.

I am sure I will be enlightened to the whys and wherefores.
I am prepared for the best and worst.

Thank you very much in advance.

Les





Littelfuse smd 'B' is 0.125A



RL

Matsuo KAH 1005/0402
P 0.20
Q 0.25
R 0.315
S 0.40
T 0.50
U 0.63

V 0.80
1 1.00
W 1.25
X 1.60
2 2.00
Y 2.50


littelfuse 1206 very fast acting ROHS
0466.125 .125 B
0466.200 .200 C
0466.250 .250 D
0466.375 .375 E
0466.500 .500 F
0466.750 .750 G
0466 001. 1.00 H
0466 1.25 1.25 J
0466 01.5 1.50 K
0466 1.75 1.75 L
0466 002. 2.00 N
0466 02.5 2.50 O
0466 003. 3.00 P
0466 004. 4.00 S
0466 005. 5.00 T

littelfuse 1206 very fast acting
0433.125 .125 B
0433.200 .200 C
0433.250 .250 D
0433.375 .375 E
0433.500 .50 F
0433.600 .60 .6
0433.750 .75 G
0433.800 .80 .8
0433 001. 1.0 H
0433 1.25 1.25 J
0433 01.5 1.5 K
0433 1.75 1.75 L
0433 002. 2.0 N
0433 02.5 2.5 O
0433 003. 3.0 P
0433 004. 4.0 S
0433 005. 5.0 T

Littelfuse 1206 fast acting ROHS
429.125 0.125 FB
429.200 0.200 FC
429.250 0.250 FD
429.375 0.375 FE
429.500 0.500 FF
429.750 0.75 FG
429 001 1.00 FH
429 007 7.0 FU
429 007L 7.0 7

1206 delay
0430.500 0.5 TF
0430 001. 1.0 TH
0430 01.5 1.5 TK
0430 002. 2.0 TN
0430 003. 3.0 TP

0603 ultrafast
0434.250 .250 D
0434.375 .375 E
0434.500 .500 F
0434.680 .680 X
0434.750 .750 G
0434 001. 1.00 H
0434 1.25 1.25 J
0434 01.5 1.50 K
0434 1.75 1.75 L
0434 002. 2.00 N
0434 02.5 2.50 O
0434 003. 3.00 P
0434 03.5 3.50 R
0434 004. 4.00 S
0434 005. 5.00 T

Littelfuse 1206 fast
0437.250 .250 D
0437.375 .375 E
0437.500 .500 F
0437.750 .750 G
0437001. 1.00 H
04371.25 1.25 J
043701.5 1.50 K
04371.75 1.75 L
0437002. 2.00 N
043702.5 2.50 O
0437003. 3.00 P
043703.5 3.50 R
0437004. 4.00 S
0437005. 5.00 T
0437007. 7.00 W
0437008. 8.00 X

Littelfuse 0603 ultrafast
0467.250 .25 D
0467.375 .375 E
0467.500 .500 F
0467.750 .750 G
0467 001. 1.00 H
0467 1.25 1.25 J
0467 01.5 1.50 K
0467 1.75 1.75 L
0467 002. 2.00 N
0467 02.5 2.50 O
0467 003. 3.00 P
0467 03.5 3.50 R
0467 004. 4.00 S
0467 005. 5.00 T

littelfuse 1206 slow blow ROhs
0468 001. 1.00 TH
0468 01.5 1.50 TK
0468 002. 2.00 TN
0468 003. 3.00 TP

Littelfuse 1206 delay ROHS
0468.500 TF
001. TH
01.5 TK
002. TN
02.5 TO
003. TP

Littelfuse 0402 very fast
0435.250 .25 +
0435.375 .375 :
0435.500 .5 o
0435.750 .75 %
0435 001. 1 l
0435 1.25 1.25 8
0435 01.5 1.5 blank
0435 1.75 1.75 X
0435 002. 2 O

vishay 0603
500 mA F
630 mA CT
750 mA G
800 mA CV
1.0 A H
1.25 A J
1.5 A K
1.6 A EF
1.75 A L
2.0 A N
2.5 A O
3.0 A P
3.15 A
3.5 A R
4.0 A S
5.0 A T

vishay 0805
500 mA F
630 mA CT
750 mA G
800 mA CV
1.0 A H
1.25 A J
1.5 A K
1.6 A
1.75 A
2.0 A N
2.5 A O
3.0 A P
3.15 A EL
3.5 A R
4.0 A S
5.0 A T

vishay 1206
500 mA F
630 mA CT
750 mA G
800 mA CV
1.0 A H
1.25 A J
1.5 A K
1.6 A EF
1.75 A L
2.0 A N
2.5 A O
3.0 A P
3.15 A EL
3.5 A R
4.0 A S
5.0 A T
6.3 A ET
.........................

0468 littelfuse 1206 slow
001. H
1.25 J
01.5 K
002. N
02.5 O
003. P
03.5 R
004. S
005. T
006. U
007. W
008. X

SF bournes 1206
F = 0.50
K = 0.80
L = 1.00
M = 1.25
P = 1.50
S = 2.00
T = 2.50
3 = 3.00
W = 4.00
Y = 5.00
Z = 7.00

CCH bussman 1206
CC12H1A 1 H
CC12H1.5A 1.5 K
CC12H2A 2 N
CC12H2.5A 2.5 O
CC12H3A 3 P
CC12H3.5A 3.5 R
CC12H4A 4 S
CC12H4.5A 4.5 X
CC12H5A 5 T

2410 TE 1206
2410SFV0.50FM C
2410SFV0.63FM S 0.6
2410SFV0.75FM/125-2 D 0.8
2410SFV1.00FM/125-2 E 1.0
2410SFV1.25FM/125-2 F 1.3
2410SFV1.50FM/125-2 G 1.5
2410SFV2.00FM/125-2 I 2.0
2410SFV2.50FM/125-2 J 2.5
2410SFV3.00FM/125-2 K 3.0
2410SFV3.15FM/125-2 V 3.2
2410SFV3.50FM/125-2 L 3.5
2410SFV4.00FM/125-2 M 4.0
2410SFV5.00FM/125-2 N 5.0
2410SFV6.30FM/125-2 O 6.3
2410SFV7.00FM/125-2 P 7.0
2410SFV8.00FM/125-2 R 8.0
2410SFV10.0FM/125-2 Q 10.0
2410SFV12.0FM/065-2 X 12.0
2410SFV15.0FM/065-2 Y 15
2410SFV20.0FM/065-2 Z 20

On Saturday, October 31, 2020 at 12:50:34 PM UTC-4, ABLE1 wrote:
On 10/31/2020 12:33 PM, KenW wrote:
Because they are cheap and can be wave soldered and last but not least
screw the buyer.


KenW


KenW,

Well that is a very honest response.

Thank You!!


Les

Yeah, but the average buyer these days demands low prices. Price is probably the defining feature when the Joe Consumer goes shopping.

In defense of smd fuses, they don't fail for no reason (except those stupid ceramic ones with the bonded metal caps), so if Joe Consumer doesn't recognize it as a fuse, he can't put a foil gum wrapper around it.

Other than a socketed fuse, they are easier to change than any other type of through the hole mounted fuse.

On Saturday, October 31, 2020 at 12:48:46 PM UTC-5, John-Del wrote:
On Saturday, October 31, 2020 at 12:50:34 PM UTC-4, ABLE1 wrote:
On 10/31/2020 12:33 PM, KenW wrote:
Because they are cheap and can be wave soldered and last but not least
screw the buyer.


KenW


KenW,

Well that is a very honest response.

Thank You!!


Les

Yeah, but the average buyer these days demands low prices. Price is probably the defining feature when the Joe Consumer goes shopping.

In defense of smd fuses, they don't fail for no reason (except those stupid ceramic ones with the bonded metal caps), so if Joe Consumer doesn't recognize it as a fuse, he can't put a foil gum wrapper around it.

Other than a socketed fuse, they are easier to change than any other type of through the hole mounted fuse.

You could do better by not using silly names like, "Joe consumer". Use "average consumer" instead. Good work though.

On 11/1/20 11:29 AM, Edward Hernandez wrote:
You could do better by not using silly names like, "Joe consumer".

**** off charger boy.
Nobody gives two ****s about your opinions.


--
"I am a river to my people."
Jeff-1.0
WA6FWi
http:foxsmercantile.com

I think you do. Are you able to chase me? Don't get out of breath.

On Sat, 31 Oct 2020 12:26:25 -0400, ABLE1
wrote:

Is there some chart that would be available to give the ability
to ID the value of this fuse and its parameters??

https://www.littelfuse.com/~/media/electronics/datasheets/fuses/littelfuse_fuse_466_datasheet.pdf.pdf
The B is 0.125A. See the "Part Marking System" section on the last
page.

I just don't understand the designing of this technology type
especially at a input voltage of 120VAC.

Regulatory compliance for adequate fire and safety protection requires
a fuse. UL doesn't care if it is user accessible or buried under a
pile of wires. If you want the UL sticker, it must have a fuse of
some sorts.

I am sure I will be enlightened to the whys and wherefores.

One must suffer before enlightenment. At least that how all the
fables, parables, anecdotes, and internet explanations are commonly
inscribed.

I am prepared for the best and worst.

Are you prepared to pay for the best? (The worst you already have in
the form of an SMT fuse). For a little more $$$, the manufacturer
might supply a PPTC resettable fuse:
https://www.littelfuse.com/products/polyswitch-resettable-ptcs.aspx
Nothing to replace when it blows. Just give it time to cool down.

Or, the manufacturer could add an SMD size fuse holder:
https://www.littelfuse.com/~/media/electronics/datasheets/fuses/littelfuse_fuse_154_154t_154l_154tl_datasheet.pdf. pdf
https://www.digikey.com/en/products/filter/fuses/139?s=N4IgjCBcoLQCxVAYygMwIYBsDOBTANCAPZQDa4ArAEwD MAHCALqEAOALlCCAL69A
However, these are NOT cheap and will not work with a 1206 size fuse.

Or, the manufacturer could switch to a much larger cartridge fuse,
which offer a PCB mount fuse holder.

Thank you very much in advance.

Y'er welcome.

Incidentally, I'm more irritated with non-resettable thermal fuses
used on tranformers and kitchen appliances. These fuses are usually
buried under a layer of difficult to remove Kapton tape.


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On 11/1/2020 5:38 PM, Jeff Liebermann wrote:
Are you prepared to pay for the best? (The worst you already have in
the form of an SMT fuse). For a little more $$$, the manufacturer
might supply a PPTC resettable fuse:
https://www.littelfuse.com/products/polyswitch-resettable-ptcs.aspx
Nothing to replace when it blows. Just give it time to cool down.


So Jeff, let me ask you.

If I would replace or jumper the B = RXEF010 resetable fuse the board
would work, meet code, and almost never have to concern myself with
it in the future??

Please correct me if I am wrong.

Thanks,

Les

On 11/1/2020 10:49 PM, ABLE1 wrote:
On 11/1/2020 5:38 PM, Jeff Liebermann wrote:
Are you prepared to pay for the best?Â* (The worst you already have in
the form of an SMT fuse).Â* For a little more $$$, the manufacturer
might supply a PPTC resettable fuse:
https://www.littelfuse.com/products/polyswitch-resettable-ptcs.aspx
Nothing to replace when it blows.Â* Just give it time to cool down.


So Jeff, let me ask you.

If I would replace or jumper the B = RXEF010Â* resetable fuse the board
would work, meet code, and almost never have to concern myself with
it in the future??

Please correct me if I am wrong.

Thanks,

Les


Sorry my bad. I forgot to look at the voltage spec.

Maybe a 250R120-R2 - 250R would do the trick.

Please advise.

Thanks!!

Les

On Sunday, November 1, 2020 at 2:06:46 PM UTC-6, Fox's Mercantile wrote:
On 11/1/20 11:29 AM, Edward Hernandez wrote:
You could do better by not using silly names like, "Joe consumer".

**** off charger boy.
Nobody gives two ****s about your opinions.


--
"I am a river to my people."
Jeff-1.0
WA6FWi
http:foxsmercantile.com

Hey guess what... I finally clicked on your little website. It did not disappoint! HHhahahah. You are a gem.

On Sun, 1 Nov 2020 20:25:14 -0800 (PST) the anus of Edward Hernandez sputtered:
Hey guess what... I finally clicked on your little website. It did not
disappoint! HHhahahah. You are a gem.

You were given useful advice at the beginning. The fact that you are too
much of a child to realize it was useful advice is not our fault.

On Sun, 1 Nov 2020 22:49:59 -0500, ABLE1
wrote:

On 11/1/2020 5:38 PM, Jeff Liebermann wrote:
Are you prepared to pay for the best? (The worst you already have in
the form of an SMT fuse). For a little more $$$, the manufacturer
might supply a PPTC resettable fuse:
https://www.littelfuse.com/products/polyswitch-resettable-ptcs.aspx
Nothing to replace when it blows. Just give it time to cool down.


So Jeff, let me ask you.

If I would replace or jumper the B = RXEF010 resetable fuse the board
would work, meet code, and almost never have to concern myself with
it in the future??

Please correct me if I am wrong.

Thanks,

Les

Would you prefer to replace the fuse with the same type and rating,
or throw the thing in the garbage, next time ?

RL

On 11/2/2020 7:51 AM, legg wrote:
On Sun, 1 Nov 2020 22:49:59 -0500, ABLE1
wrote:

On 11/1/2020 5:38 PM, Jeff Liebermann wrote:
Are you prepared to pay for the best? (The worst you already have in
the form of an SMT fuse). For a little more $$$, the manufacturer
might supply a PPTC resettable fuse:
https://www.littelfuse.com/products/polyswitch-resettable-ptcs.aspx
Nothing to replace when it blows. Just give it time to cool down.


So Jeff, let me ask you.

If I would replace or jumper the B = RXEF010 resetable fuse the board
would work, meet code, and almost never have to concern myself with
it in the future??

Please correct me if I am wrong.

Thanks,

Les

Would you prefer to replace the fuse with the same type and rating,
or throw the thing in the garbage, next time ?

RL



Now that I know there might be a resetable fuse available.

What I was thinking was to replace the fuse with a "resetable" as
suggested by Jeff. A resetable that had a compatible rating and
was available at a quantity of maybe 10 each or so. That way,
I would have some available for other boards in the future should
I need any. It is simple, as opposed to buying a whole new board
for $25.00 + Tariff + Tax + Shipping + etc. etc. for the cost of
a $0.80?? part.

Les

On Sunday, November 1, 2020 at 2:06:46 PM UTC-6, Fox's Mercantile wrote:
On 11/1/20 11:29 AM, Edward Hernandez wrote:
You could do better by not using silly names like, "Joe consumer".
**** off charger boy.
Nobody gives two ****s about your opinions.


--
"I am a river to my people."
Jeff-1.0
WA6FWi
http:foxsmercantile.com

Look at such a great effort all for me! Thanks comic book boy. lol.

On Mon, 2 Nov 2020 08:35:04 -0500, ABLE1
wrote:

On 11/2/2020 7:51 AM, legg wrote:
On Sun, 1 Nov 2020 22:49:59 -0500, ABLE1
wrote:

On 11/1/2020 5:38 PM, Jeff Liebermann wrote:
Are you prepared to pay for the best? (The worst you already have in
the form of an SMT fuse). For a little more $$$, the manufacturer
might supply a PPTC resettable fuse:
https://www.littelfuse.com/products/polyswitch-resettable-ptcs.aspx
Nothing to replace when it blows. Just give it time to cool down.


So Jeff, let me ask you.

If I would replace or jumper the B = RXEF010 resetable fuse the board
would work, meet code, and almost never have to concern myself with
it in the future??

Please correct me if I am wrong.

Thanks,

Les

Would you prefer to replace the fuse with the same type and rating,
or throw the thing in the garbage, next time ?

RL



Now that I know there might be a resetable fuse available.

What I was thinking was to replace the fuse with a "resetable" as
suggested by Jeff. A resetable that had a compatible rating and
was available at a quantity of maybe 10 each or so. That way,
I would have some available for other boards in the future should
I need any. It is simple, as opposed to buying a whole new board
for $25.00 + Tariff + Tax + Shipping + etc. etc. for the cost of
a $0.80?? part.

Les

You're going to buy a part, so buy the right one.

A PTC fuse won't do the same job - they require more info than
you have to apply reliably.

RL

On Sun, 1 Nov 2020 14:09:56 -0800 (PST) the anus of Edward Hernandez sputtered:
I think you do. Are you able to chase me? Don't get out of breath.

Stop being such a troll and go away. You got useful advice at the outset
on your charger in this group. Now you are simply acting like a spoiled
child who was told "no candy before dinner" by Mom & Dad when you really
wanted some candy.

On 11/2/2020 10:39 AM, legg wrote:
On Mon, 2 Nov 2020 08:35:04 -0500, ABLE1
wrote:

On 11/2/2020 7:51 AM, legg wrote:
On Sun, 1 Nov 2020 22:49:59 -0500, ABLE1
wrote:

On 11/1/2020 5:38 PM, Jeff Liebermann wrote:
Are you prepared to pay for the best? (The worst you already have in
the form of an SMT fuse). For a little more $$$, the manufacturer
might supply a PPTC resettable fuse:
https://www.littelfuse.com/products/polyswitch-resettable-ptcs.aspx
Nothing to replace when it blows. Just give it time to cool down.


So Jeff, let me ask you.

If I would replace or jumper the B = RXEF010 resetable fuse the board
would work, meet code, and almost never have to concern myself with
it in the future??

Please correct me if I am wrong.

Thanks,

Les

Would you prefer to replace the fuse with the same type and rating,
or throw the thing in the garbage, next time ?

RL



Now that I know there might be a resetable fuse available.

What I was thinking was to replace the fuse with a "resetable" as
suggested by Jeff. A resetable that had a compatible rating and
was available at a quantity of maybe 10 each or so. That way,
I would have some available for other boards in the future should
I need any. It is simple, as opposed to buying a whole new board
for $25.00 + Tariff + Tax + Shipping + etc. etc. for the cost of
a $0.80?? part.

Les

You're going to buy a part, so buy the right one.

A PTC fuse won't do the same job - they require more info than
you have to apply reliably.

RL


Ok??

RL,

What additional information would I need "to buy the right one"??

120VAC
..125 amps
fast acting
a good one shows 5.9 ohms while installed on board
€“ 55 deg C to 90 deg C.

So maybe this one??

https://www.littelfuse.com/~/media/e...asheet.pdf.pdf

The LVR025S to be specific.

BTW this is more of an experiment or some personal edification.

As is said; Need to learn something new ever day.

Thanks for any input. (Quality input that is)

Les

On 11/2/20 9:20 AM, Edward H. wrote:
Look at such a great effort all for me!

Oh look, monkey boy figured out how to change his name.

--
"I am a river to my people."
Jeff-1.0
WA6FWi
http:foxsmercantile.com

On Sun, 1 Nov 2020 22:49:59 -0500, ABLE1
wrote:

On 11/1/2020 5:38 PM, Jeff Liebermann wrote:
Are you prepared to pay for the best? (The worst you already have in
the form of an SMT fuse). For a little more $$$, the manufacturer
might supply a PPTC resettable fuse:
https://www.littelfuse.com/products/polyswitch-resettable-ptcs.aspx
Nothing to replace when it blows. Just give it time to cool down.

So Jeff, let me ask you.

If I would replace or jumper the B = RXEF010 resetable fuse the board
would work, meet code, and almost never have to concern myself with
it in the future??

No. I would replace it with as close to the original SMD fuse as
possible. In an emergency, I might replace the tiny SMD fuse with a
much larger fuse with wire leads. If doing development work on a
prototype, I would probably install a rather expensive socket and
rectangular fuse. However, for consumer use, it will always be the
original fuse.

The reason is that I don't know anything about the device that you
own. Most important, I don't know what it will do if a low AC voltage
is applied to the device. That's what will happen with a PTC
resettable fuse. The circuit does not go to completely open when the
PTC fuse is tripped. It goes to a fairly high resistance, and then
only as long as the fuse remains hot. To keep it hot, there has to be
a high current going through the fuse. That means there's power
applied to the rest of the PC board while the fuse is tripped. If you
look at the specs, that's the "hold current". Done correctly, that
will keep the fuse warm, and the power MOSTLY removed from the rest of
the circuit. Done wrong, it is possible that the fuse will cause the
device to cycle on and off repeatedly as the PTC fuse cycles through
hot and cold cycles. There are places and devices where a resettable
fuse is appropriate and safe. However, since I have no idea what
you're working with, I can't predict what will happen if you cram in a
PPTC resettable fuse and certainly don't want to take the risk
suggesting you do something that might be unsafe.

Also, is this really a problem that is worth solving? I doubt it. Put
in the correct fuse and you won't have to worry about the device
burning your house down.

Incidentally, I once repaired a small 13.6V 30A switching power
supply, which had a PPTC resettable fuse in the AC line. The problem
was obvious as there was a hole burned into the PCB where the PTC
resettable fuse had been. I could find no part number or specs on the
fuse making replacement difficult. I soon discovered why they used a
resettable fuse. It wasn't for convenience or size. It was because
the inrush current on this power supply was so high, that even a
slow-blo fuse would blow up if switched on with a 15A load. The
designer decided to use the PPTC fuse as an inrush current limiter,
which is a really bad idea. At some point along the load curve and
near maximum current, the operating point landed on the transition
line between low and high resistance. Since there was no hysteresis
in the transition line, the maximum power dissipation point for the
PPTC fuse was also somewhere along the curve. As bad luck would have
it, the customer's was operating almost on the same point of the
curve, causing the PTC fuse to become very hot. After a few days of
this kind of abuse, it burned a hole in the PCB and carbonized the PTC
fuse.

I made a few measurements and calculations and found a higher current
replacement PTC fuse. That brought the PTC fuse transition line to
somewhat higher than the maximum current. That fixed one problem and
created a new problem. The PTC would never trip because the
over-current protection in the power supply would turn down the power
supply before the PTC fuse was able to do the same. However, the
over-current protection was set to begin at about 10A above the
maximum output current and had no hysteresis. So, this mess is going
to require some redesign. I changed a few parts to bring the
over-current threshold to the maximum rated current and enabled
hysteresis by installing a resistor that the designer forgot. I
replaced the PTC fuse with a Slo-Blo conventional fuse, and inserted a
PTC thermistor inrush current limiter intended only to prevent blowing
the fuse under normal operation. Problem solved and it's been working
just fine for about 3 years.

Are you prepared to do something similar with your "circuit board"?

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Monday, November 2, 2020 at 1:13:44 PM UTC-6, soft-stool Fox Comics queefed:

Oh look, monkey boy figured out how to change his name.

I'm learning a lot everyday old fella. Like how much smaller you've become since I first ran into you. Here I thought, "41 yrs on usenet! Wowee!" Ahhaha. You continue to shrink and your posts seem so much softer.

On 11/2/2020 2:39 PM, Jeff Liebermann wrote:
On Sun, 1 Nov 2020 22:49:59 -0500, ABLE1
wrote:

On 11/1/2020 5:38 PM, Jeff Liebermann wrote:
Are you prepared to pay for the best? (The worst you already have in
the form of an SMT fuse). For a little more $$$, the manufacturer
might supply a PPTC resettable fuse:
https://www.littelfuse.com/products/polyswitch-resettable-ptcs.aspx
Nothing to replace when it blows. Just give it time to cool down.

So Jeff, let me ask you.

If I would replace or jumper the B = RXEF010 resetable fuse the board
would work, meet code, and almost never have to concern myself with
it in the future??

No. I would replace it with as close to the original SMD fuse as
possible. In an emergency, I might replace the tiny SMD fuse with a
much larger fuse with wire leads. If doing development work on a
prototype, I would probably install a rather expensive socket and
rectangular fuse. However, for consumer use, it will always be the
original fuse.

The reason is that I don't know anything about the device that you
own. Most important, I don't know what it will do if a low AC voltage
is applied to the device. That's what will happen with a PTC
resettable fuse. The circuit does not go to completely open when the
PTC fuse is tripped. It goes to a fairly high resistance, and then
only as long as the fuse remains hot. To keep it hot, there has to be
a high current going through the fuse. That means there's power
applied to the rest of the PC board while the fuse is tripped. If you
look at the specs, that's the "hold current". Done correctly, that
will keep the fuse warm, and the power MOSTLY removed from the rest of
the circuit. Done wrong, it is possible that the fuse will cause the
device to cycle on and off repeatedly as the PTC fuse cycles through
hot and cold cycles. There are places and devices where a resettable
fuse is appropriate and safe. However, since I have no idea what
you're working with, I can't predict what will happen if you cram in a
PPTC resettable fuse and certainly don't want to take the risk
suggesting you do something that might be unsafe.

Also, is this really a problem that is worth solving? I doubt it. Put
in the correct fuse and you won't have to worry about the device
burning your house down.

Incidentally, I once repaired a small 13.6V 30A switching power
supply, which had a PPTC resettable fuse in the AC line. The problem
was obvious as there was a hole burned into the PCB where the PTC
resettable fuse had been. I could find no part number or specs on the
fuse making replacement difficult. I soon discovered why they used a
resettable fuse. It wasn't for convenience or size. It was because
the inrush current on this power supply was so high, that even a
slow-blo fuse would blow up if switched on with a 15A load. The
designer decided to use the PPTC fuse as an inrush current limiter,
which is a really bad idea. At some point along the load curve and
near maximum current, the operating point landed on the transition
line between low and high resistance. Since there was no hysteresis
in the transition line, the maximum power dissipation point for the
PPTC fuse was also somewhere along the curve. As bad luck would have
it, the customer's was operating almost on the same point of the
curve, causing the PTC fuse to become very hot. After a few days of
this kind of abuse, it burned a hole in the PCB and carbonized the PTC
fuse.

I made a few measurements and calculations and found a higher current
replacement PTC fuse. That brought the PTC fuse transition line to
somewhat higher than the maximum current. That fixed one problem and
created a new problem. The PTC would never trip because the
over-current protection in the power supply would turn down the power
supply before the PTC fuse was able to do the same. However, the
over-current protection was set to begin at about 10A above the
maximum output current and had no hysteresis. So, this mess is going
to require some redesign. I changed a few parts to bring the
over-current threshold to the maximum rated current and enabled
hysteresis by installing a resistor that the designer forgot. I
replaced the PTC fuse with a Slo-Blo conventional fuse, and inserted a
PTC thermistor inrush current limiter intended only to prevent blowing
the fuse under normal operation. Problem solved and it's been working
just fine for about 3 years.

Are you prepared to do something similar with your "circuit board"?



Jeff,

Actually no I am not. This is for a wall clock timer controlled
correcting board. Basically upon a signal from the master clock
the clock then adjusts to the right time.


I was thinking of trying a retro fix of board to see if it would
work. I realized early on that I would probably not do this, but,
I wanted to get opinions on the plus and minus of choices.

Since you put the possible issues the way you did I will totally
scratch that idea and move on to other stuff. However, I doubt
there would be any major issues at the current draw max of .5 amps.
The clock would just stop running!!

Thanks for the detailed typing. All very helpful and informative
to my brain antique brain. Learning new stuff is always beneficial.

Thanks again and have a good week.

Les

On Monday, November 2, 2020 at 11:21:49 AM UTC-5, Mary R. Smith wrote:
On Sun, 1 Nov 2020 14:09:56 -0800 (PST) the anus of Edward Hernandez sputtered:
I think you do. Are you able to chase me? Don't get out of breath.

Stop being such a troll and go away.

I encourage everyone in all the trades to come here, whether its 'horsing around' like this or not. Like on a construction site: everyone gangs up on the person getting the attention. Like in the powder room. All the ladies gang up on the girl with the angelic face withbomb shell body.

On Sunday, November 29, 2020 at 9:05:08 AM UTC-5, Transition Zone wrote:
On Monday, November 2, 2020 at 11:21:49 AM UTC-5, Mary R. Smith wrote:
On Sun, 1 Nov 2020 14:09:56 -0800 (PST) the anus of Edward Hernandez sputtered:
I think you do. Are you able to chase me? Don't get out of breath.

Stop being such a troll and go away.
I encourage everyone in all the trades to come here, whether its 'horsing around' like this or not. Like on a construction site: everyone gangs up on the person getting the attention. Like in the powder room. All the ladies gang up on the girl with the angelic face withbomb shell body.

OK well, not in the powder room (but everywhere else).

Well, it has become clear that this individual is an Idiot in Search of a Village - and has found this venue. Given that the purpose of the Village Idiot is to make everyone else in the village look good by comparison, I would posit that this Idiot is performing its job in a most masterful way!

Peter Wieck
Melrose Park, PA