2r55a

[mike9h29]

Hi,

Can some one give me equivalent to SCK 2R55A please?

I Think it is a NTC Thermistor (I found this info from a post on this site!)

Thanks

Mario

[Toasty]

Re: 2r55a

SCK-2R55A
2.5Ω - Zero power resistance (25°C)
5A - max steady current
120mΩ - resistance at max current (25°C)
-40 to +170 °C - operating temp range

[mike9h29]

Re: 2r55a

SCK-2R55A
2.5Ω - Zero power resistance (25°C)
5A - max steady current
120mΩ - resistance at max current (25°C)
-40 to +170 °C - operating temp range

Thanks for the info.

I am trying to source this part, but I cant find it on ebay.

Is there any other part number that is equivalent to this part please?

Thanks

Mario

[Toasty]

Re: 2r55a

Using those specs, try DigiKey or Mouser.

Inrush limiter

I found 1 that is close.

Hint: be a little "loose" with the specs.

[mike9h29]

Re: 2r55a

Using those specs, try DigiKey or Mouser.

Inrush limiter

I found 1 that is close.

Hint: be a little "loose" with the specs.

Thanks. Will check again.

Is it normal for these to crack when there`s a surge?

I was testing a TFT PSU that was blowing the fuse every time.

I fried 5 fuses before I found out that the bridge rectifier is shorted!

Then I found this part cracked.

Mario

[Toasty]

Re: 2r55a

heh

No, it's normal for these to crack when there is a problem... They are in -series- with the hot side (or should be...) of the mains.

That's why you should be using this circuit to test before fully applying line power. Saves a box of fuses.



If the light comes on full and stays that way, then there's something wrong on the mains side.

If it comes on briefly and goes dark/dim (I use a clear bulb), then the mains side is probably fine and the problem lies deeper in the supply.

Toast

[mike9h29]

Re: 2r55a

heh

No, it's normal for these to crack when there is a problem... They are in -series- with the hot side (or should be...) of the mains.

That's why you should be using this circuit to test before fully applying line power. Saves a box of fuses.



If the light comes on full and stays that way, then there's something wrong on the mains side.

If it comes on briefly and goes dark/dim (I use a clear bulb), then the mains side is probably fine and the problem lies deeper in the supply.

Toast

Wow!

Many thanks for your help.

Will use the bulb to test psus in the future.

Mario

[Toasty]

Re: 2r55a

Just change the bulb wattage or add another in parallel to increase the current allowed. Some bigger (wattage) supplies need more *oomph* to get started.

Did you find the replacement (it was at DigiKey).

[mike9h29]

Re: 2r55a

Just change the bulb wattage or add another in parallel to increase the current allowed. Some bigger (wattage) supplies need more *oomph* to get started.

Did you find the replacement (it was at DigiKey).

to tell you the truth I did not had time to search for it at Digikey today. Hopfully I will search for it tonight.

I have another small question regarding electronics. maybe you can help me please?

What is a starting capacitor or resistor please?

Thanks

Mario

[Toasty]

Re: 2r55a

>>What is a starting capacitor or resistor please?<<

In what type of device?

[maybenever]

Re: 2r55a

In the old days of fuse boxes, my Dad would screw a bulb in place of a fuse, then take the circuit apart until the light when out.
No one but he and I could seem to understand it.

[Toasty]

Re: 2r55a

In the old days of fuse boxes, my Dad would screw a bulb in place of a fuse, then take the circuit apart until the light when out.
No one but he and I could seem to understand it.

Either you lived in an old house.......


.....or you've just severely dated yourself...

[mike9h29]

Re: 2r55a

>>What is a starting capacitor or resistor please?<<

In what type of device?

In a switch mode psu.

[Toasty]

Re: 2r55a

The startup resistor would be what gets the main switcher going until the PWM control circuit can take over. That can only happen if there is sufficient voltage to drive the PWM chip. Its a power resistor that is connected to the base/gate of the main switcher.

Startup capacitor in smps keeps the PWM controller running (stores energy) until the power fully comes up.

[mike9h29]

Re: 2r55a

The startup resistor would be what gets the main switcher going until the PWM control circuit can take over. That can only happen if there is sufficient voltage to drive the PWM chip. Its a power resistor that is connected to the base/gate of the main switcher.

Startup capacitor in smps keeps the PWM controller running (stores energy) until the power fully comes up.

Thanks again for your detailed reply!

So, I have a monitor (I posted in the monitor section already), that works fine if I switch it on 1 second after I switch the wall socket on. But, If I switch the Main Socket on and leave the monitor off for more than 5 seconds, it will not switch on.

Could this be a Startup Capacitor / Resistor issue please?

Thanks

Mario

[Toasty]

Re: 2r55a

Not familiar enough with monitors to venture a guess. You need to continue the discussion that you started over there. From what I read, a bad regulator or something on the logic board makes sense.