DELL M1730 LAPTOP PSU HA230PS0 - Sparking component - help please

[Markie76]

Hi Guys,

I have a Dell M1730 which is in restricted performance mode and in the BIOS the PSU is showing as unknown.

The PSU model is HA230PS0-00 REV:A00 and the blue LED comes on and the output is over 19.5v and the laptop powers up - but battery isn't charging (that may due to separate batt issue) and the laptop is in reduced performance mode.

I opened up the PSU unit to check the continuity of the Dell genuine 'signal' wire and the first thing I noticed was a component which looks like it is self destructing and there are brown marks on the component next to it.

On the PCB it is marked as 'TH3' and the first time I powered up the PSU open & plugged in to laptop - some sparks came out the top for about half a second.

Please see pics attached for PSU P/N/specs, TH3 & it self-destructing.

Before I do anything else I wanted to ask for your help;

1. Would anyone know/can suggest the part number for TH3?

2. Does this need to be replaced straight away or it doesn't impact on the overall performance of the psu?

3. Is failure of TH3 isolated or the result of something else also failing?

Thx.

[budm]

Re: DELL M1730 LAPTOP PSU HA230PS0 - Sparking component - help please

That is thermistor which is for the in-rush current limiter used in the primary side, it is connected after the Main AC fuse. What resistance does it show right now? You usually do not see this kind of damage, unless there is problem in the circuit which is drawing too much current exceeding the current limit of this device.

[Markie76]

Re: DELL M1730 LAPTOP PSU HA230PS0 - Sparking component - help please

That is thermistor which is for the in-rush current limiter used in the primary side, it is connected after the Main AC fuse. What resistance does it show right now? You usually do not see this kind of damage, unless there is problem in the circuit which is drawing too much current exceeding the current limit of this device.

Thank you for your reply and apologies for the delay in replying but I have been away with work.

The pcb side of TH3 contacts show the following resistance;

Initial touch -28.5 ohm
30 seconds - 27.1 ohm
60 seconds - 26.2 ohm
120 seconds - 25.5 ohm

It changes slightly over time but settles at 25.5 if that is significant, I am using a budget UNI-T auto-ranging digital multimeter .

Thanks,

Mark.

[budm]

Re: DELL M1730 LAPTOP PSU HA230PS0 - Sparking component - help please

That is way too high, at 28 Ohms, with 120V circuit, for 230W power supply, I expect it to around 2~5 Ohms or so when cold, this inrush limiter is the NTC type, as it is heated up the resistance will go down.
See the calculator:
http://www.ametherm.com/inrush-curre...t-limiter.html
http://www.ametherm.com/inrush-curre...ta-sheets.html

[Markie76]

Re: DELL M1730 LAPTOP PSU HA230PS0 - Sparking component - help please

That is way too high, at 28 Ohms, with 120V circuit, for 230W power supply, I expect it to around 2~5 Ohms or so when cold, this inrush limiter is the NTC type, as it is heated up the resistance will go down.
See the calculator:
http://www.ametherm.com/inrush-curre...t-limiter.html
http://www.ametherm.com/inrush-curre...ta-sheets.html

Thanks for the reply & links but I'm not getting anywhere.

Vpeak - the mains is 240v
Capacitance - what is my capacitance? The psu is rated 19.5v 11.8a 230W

If you can suggest a suitable replacement thermistor that would be great.

Thanks,

Mark.

[budm]

Re: DELL M1730 LAPTOP PSU HA230PS0 - Sparking component - help please

Vpeak = line voltage x 1.414, so 240 x 1.414 = 339V, then look at the capacitance value of the main filter cap (there should be big electrolytic cap laying on its side) and put in those numbers in the calculator to find the J rating then look at the that can handle the Joules rating.

[Markie76]

Re: DELL M1730 LAPTOP PSU HA230PS0 - Sparking component - help please

ok, I've delved further into the psu - the capacitor is marked 450v 220uf;

Vpeak: 339v
Capacitance: 220 uf
Total energy = 12.6 joules

So I need a thermistor rated above 12.6j so something like 15 or 20?

Also, there is lots of white stuff around components - looks like bathroom sealant but very stiff - what is it?

[Agent24]

Re: DELL M1730 LAPTOP PSU HA230PS0 - Sparking component - help please

Also, there is lots of white stuff around components - looks like bathroom sealant but very stiff - what is it?

Glue of some kind. They use it to stop the larger\heavier components moving around during assembly. And if you're paranoid, they also use it as a timed self-destruct feature, when it dries out and can become conductive.

(Actually I don't know about the white stuff, but the brown\tan stuff often gets conductive with age)

[budm]

Re: DELL M1730 LAPTOP PSU HA230PS0 - Sparking component - help please

What is the diameter of the old one? around 8 mm or 10mm?

[Markie76]

Re: DELL M1730 LAPTOP PSU HA230PS0 - Sparking component - help please

What is the diameter of the old one? around 8 mm or 10mm?

Its a bit tricky to measure but 7-8mm looks about right.

The TH3 pcb contacts are about 8mm centre to centre.

Glue of some kind. They use it to stop the larger\heavier components moving around during assembly. And if you're paranoid, they also use it as a timed self-destruct feature, when it dries out and can become conductive.

(Actually I don't know about the white stuff, but the brown\tan stuff often gets conductive with age)

There's certainly a lot of the white stuff in the psu/case.
Going conductive is not very good!

[budm]

Re: DELL M1730 LAPTOP PSU HA230PS0 - Sparking component - help please

This one should be OK: http://www.ametherm.com/datasheets/sl1025002.html
25 Ohms (that will limit the Pk current @ 230V (325Vp) to about 13A which the bridge rectifier should be able to handle), 20j, Max 2A steady state (your power supply is rated at 230W, so the steady state with 90% effi will be about 1.1A). This is the closest one I come up with, it will dissipate about 1W of power with 1A.
Please note that I do not know what the peak inrush current of this power supply is designed for.
You can also contact AMETHERM for verification.

[momaka]

Re: DELL M1730 LAPTOP PSU HA230PS0 - Sparking component - help please

There's certainly a lot of the white stuff in the psu/case.
Going conductive is not very good!

The white glue/silicone isn't conductive. Only the tan/brown glue is, but it takes some heat and several years to get to that point. It is also slightly acidic, because it often corrodes traces and terminals on components.

That said, the white glue in your adapter is NOT regular bathroom/kitchen silicone. Bathroom/kitchen silicone should NOT be used in electronics precisely because it is slightly acidic as well when it dries and can damage copper traces.