What is this part.....

[Welchs101]

Hi, I am working on a Dell E171FP and it blew a fuse. I saw this green device looked like it had a "hole" in it.........

I de-soldered the part and included pictures

I am not sure what this is.

This part came off the main power supply board. I show the main board and where the part came from ......see red box....part is removed from board and not in the pic.

Note: When you plug in power to the main board.......it blows a fuse.

[etnietering]

Re: What is this part.....

That is the inrush current limiter. It's a NTC thermistor, meaning that as the temperature increases, the resistance decreases. When you first plug the board in, the large primary capacitor is drained, and wants to fill up. Because of this, sometimes the inrush current can be many 10s of amps. The inrush limiter limits this current so that fuses and circuit breakers don't pop, and so that the lights don't dim. If this failed short (it looks like it failed), then the inrush current could be popping the fuse. Measure it's resistance. If you get more than a few ohms, it's probably ok, and the problem is someplace else, but if you get <1 ohm it's probably blown. Something like this would probably work http://search.digikey.com/scripts/Dk...me=317-1181-ND
Also, what types of fuses are you using? Power supplies usually use the slow-blow variety for this very reason, and if you're replacing them with the quick-blow type this might be popping it.

[stj]

Re: What is this part.....

probably a ptc, a type of resistor used to limit startup power.

check the rectifier & main capacitor for shorts.

[PlainBill]

Re: What is this part.....

As stj said, check bridge rectifier (black rectangle between large cap and the toroid), the main filter cap for shorts. Also check the power FET (device on the heat sink at the bottom of the picture).

PlainBill

[Welchs101]

Re: What is this part.....

This device.........the resistance across the leads measured ~ 9.1ohms. But there is definitely a hole in this ........

The big capacitor .......seems to be ok.........cap value measured is ~ 100uF.

The rectifier you spoke of ......is this the black rectangular (thin) device?

[Welchs101]

Re: What is this part.....

ok.....i have enclosed a pic of what i believe is the same recifier that i have part number D2SB.........

When i measure the resistance between pin 1 and pin2 i measure a short.......

From the enclosed pic i dont think a short is supposed to be between pins 1 and 2............is this right?

[PlainBill]

Re: What is this part.....

ok.....i have enclosed a pic of what i believe is the same recifier that i have part number D2SB.........

When i measure the resistance between pin 1 and pin2 i measure a short.......

From the enclosed pic i dont think a short is supposed to be between pins 1 and 2............is this right?

You are correct. Assume the thermistor is bad. Replace it and the rectifier. Also, check the resistance across the large cap while it is soldered in place. That should pick up a shorted FET.

PlainBill

[momaka]

Re: What is this part.....

Here's what you should get for the bridge rectifier when measured with a DMM in resistance setting (for best results, take it out of the circuit):
#1) Open circuit (infinity Ohms) between pins 2 and 3 (or if you're testing it in circuit, you might get a few 10s of kOhms). If you get a short or very low resistance (less than 1 kOhm), take out the bridge rectifier out of the circuit and measure it again.
#2) With the positive (+) DMM probe on pin 1 (+) and the negative (-/COM) probe on either pins 2 or 3, you should get open circuit.
#3) With the negative (-) DMM probe on pin 4 (-) and the positive (+) probe on either pins 2 or 3, you should get open circuit again.
#4) With the positive (+) DMM probe on pin 4 (-) and the negative (-/COM) probe on either pins 2 or 3, you should get some resistance (probably around a few 100 Ohms).
#5) With the negative (-) DMM probe on pin 1 (+) and the positive (+) probe on either pins 2 or 3, you should get some resistance (same as in #4).

By the way, this PSU board looks like the same model as the one in your Dell 1504FP monitor. See what readings you get on that PSU board.

From the enclosed pic i dont think a short is supposed to be between pins 1 and 2............is this right?

A short - no. But some resistance is normal if you have the probes arranged as in #5.

[seanc]

Re: What is this part.....

Momaka, I take it that information is applicable to all bridge rectifiers?
If I get readings in MΩ but not in kΩ or Ω, is it safe to think that the rectifier is OK?

[PlainBill]

Re: What is this part.....

Momaka, I take it that information is applicable to all bridge rectifiers?
If I get readings in MΩ but not in kΩ or Ω, is it safe to think that the rectifier is OK?

It depends on the meter you are using. Momaka's directions work well if you are using a VOM, not so well if you are using a DMM. Let's use the Vishay 3KBP08M as an example. This is in a rectangular package with one corner missing. We will call the lead on that end pin 1. The pins are numbered 1-4, and have symbols on the package as follows.
1 +
2 ~
3 ~
4 -

Test 1. Set your DMM on the 200 ohm scale. With the rectifier out of circuit, measure between the following pins:

1-2, 1-3, 1-4, 2-3, 2-4, 3-4. All readings should show open - greater than 200 ohms. If one or more read below 200 ohms with a DMM AND the fuse keeps blowing, the bridge is bad. If the fuse doesn't blow, your DMM probably uses a voltage over 0.5 volts to test resistance.

Test 2. Set your DMM in the diode scale. Hold the black lead on pin 1. You should get readings of about .5 to .7 when you touch the red lead to pin 2 and pin 3. Now hold the red lead on pin 4. You should get readings of .5 to .7 when you touch the black lead to pin 2 and pin 3.

PlainBill

[seanc]

Re: What is this part.....

Cheers PlainBill Rectifier working fine over here. Now off to investigate other things (in an iMac G5 PSU).

[NxB]

Re: What is this part.....

I haven't found too many dead rectifiers. Only one recently. It had continuity between one of the AC lines and - in one direction.

[seanc]

Re: What is this part.....

Mm, well I'm going on a remove and test everything adventure, it's so packed in that PSU I keep finding more diodes each time I remove a heatsink. One more heatsink to go, run out of solder wick.

[Welchs101]

Re: What is this part.....

Hi,

The rectifier that is shorted is shown in the two enclosed pics. My question is what do i replace it with. When i type in D2SB into Mouser a lot of parts come up..........and when i click on the datasheet none of them say D2SB ....instead they something like D6SB......so i am not sure what to replace this regulator with.

Does anyone have any suggestions?

[stj]

Re: What is this part.....

d2sb?0

1.5amp rectifier.
the ? is any number from 2 to 8
it's the maximum voltage in hundreds.

so it's 600v 1.5amp.
i wouldnt put something that small in, i'd go for a 4amp or higher rectifier.

a d6sb80 if it will fit looks good.
6amp 800v

[Welchs101]

Re: What is this part.....

thanks.

How do i know what the ? is for my particular part.

I dont see a "D2SB?0"......i dont see the "#0" all i see is the D2SB on the package. Below the D2SB i see a 28..........

[PlainBill]

Re: What is this part.....

thanks.

How do i know what the ? is for my particular part.

I dont see a "D2SB?0"......i dont see the "#0" all i see is the D2SB on the package. Below the D2SB i see a 28..........

And a 60. So the original part is rated 1.5A, 600V .

PlainBill

[Welchs101]

Re: What is this part.....

Ok, thanks.

Just want to make sure i understand how you guys came up with the 600V, 1.5A.

You determined the 600V because of the "60".....is this right?

How did you determine the 1.5A?

Also, as STJ said i should replace this with a 4A 800V.......

[PlainBill]

Re: What is this part.....

Ok, thanks.

Just want to make sure i understand how you guys came up with the 600V, 1.5A.

You determined the 600V because of the "60".....is this right?

How did you determine the 1.5A?

Also, as STJ said i should replace this with a 4A 800V.......

If you Google D2SB you will get a number of hits; all of them point to two additional numbers after the D2SB. If you choose D2SB60 you wind up with a datasheet that looks remarkably like the part in your picture. The datasheet says the part is a 1.5A, 600V part. Searching on Digikey for a 1.5A 600V bridge rectifier gives KBP06G-ND as the only part with the proper form factor, and it costs $0.67, certainly a reasonable cost. HOWEVER, that part failed, and you can't go ordering 1 part every time you need it. It's nice to have a reserve.

I suspect STJ's logic goes this way. "Monitors don't take a lot of power, computer power supplies do. So let's upgrade by specifying a 4A, 800V part. This should be adequate for a small computer power supply. This gives KBL08-E4/51GI-ND, at $0.94 each, still a reasonable cost."

NOW, I don't fully agree with STJ. Failing caps are a constant problem with monitors; bad bridge rectifiers aren't. There is also the matter of physical size. But at the same time I won't claim he is clearly wrong, because he isn't.

PlainBill

[Welchs101]

Re: What is this part.....

In an early post someone suggested a replacement "Inrush current limiter" but the suggested replacement i think has a resistance of 12ohm........i measured ~ 9ohms on the one that i want to replace.

So it got me to thinking ..........what do i need.

The marking (see original pic) is SCK083



This web site has sck type products but to be honest i am not sure what i need. I would like to order something from digikey if possible. Any ideas?