Bush (Vestel) led40127fhdcntd - turns off and on repeatedly

[ap823]

I have replaced one burnt thermistor with a new 10 Ohm one (https://uk.rs-online.com/web/p/thermistor-ics/1857867), left the other old ones in place as they did not look damaged.
The TV is working fine again, hopefully this will be a permanent fix.
Thanks to this forum and specifically to lotas and slybunda for detailed guidance.

[lotas]

Yes, I had to remove two of 10 and put a jumper in the place of one and set it to 20 in the place of the other.

[ap823]

I have opened the TV, and can see that TH2 (just one of the three) thermistor is burnt, photo attached. I do not see any markings, but based on the earlier post from slybunda it must be SCK 102.

lotas, I see you have suggested to replace it with 20 Ohm (https://www.badcaps.net/forum/troubl...e9#post1867354), is that right? or did you mean replacing two of the old ones with one 20 Ohm? I believe slybunda said original ones were 10 Ohm each.

thanks in advance

[ap823]

Hi,

I have Toshiba TV 75u6763db, now 6 years old, experiencing symptoms, exactly as slybunda has described: works fine but when entering standby mode after a couple of seconds it powers back on and then keeps turning off and on..

I did not open the TV yet so can't at present confirm if the same thermistors are burnt.

slybunda – is your TV still working a year after your repair?

I am also in the UK, so would you still advise to use NTC 1512 Thermistor (https://uk.rs-online.com/web/p/thermistor-ics/1857833)? Any other tips or advise for DIY troubleshooting and repair?

Thanks in advance

[slybunda]

Re: Bush (Vestel) led40127fhdcntd - turns off and on repeatedly

just an update, tv is still going great. still dont get why the thermistors popped. i do feel like getting a working tv with smashed screen and using its powerboard for full recap and upgrade of other components and to keep as spare? what way can switch over with no downtime.

[slybunda]

Re: Bush (Vestel) led40127fhdcntd - turns off and on repeatedly

TV still doing great. was wondering how long are these thermistors supposed to last when used as inrush current limiters? i thought they should go 10-15 years atleast?

[slybunda]

Re: Bush (Vestel) led40127fhdcntd - turns off and on repeatedly

Changes the third one too. Tv is back on the wall and woring great

[slybunda]

Re: Bush (Vestel) led40127fhdcntd - turns off and on repeatedly

hey all, i replaced the 2 thermistors and now its working properly. tv turns off and stays off.
question is now, the 3rd thermistor on the board that is not blown up should i replace it too or leave it as it is?
had to buy a 5 pack of thermistors total cost was £2.90ish so iv got 3 left.
got to thank everyone for their support.

[slybunda]

Re: Bush (Vestel) led40127fhdcntd - turns off and on repeatedly

38.5ohms and 226kohms - These are no longer workers, especially the second one.

Thanks for the reply, did you have a look at the specs of the tdk ones i posted above? Would they be safe to use?

[lotas]

Re: Bush (Vestel) led40127fhdcntd - turns off and on repeatedly

38.5ohms and 226kohms - These are no longer workers, especially the second one.

[slybunda]

Re: Bush (Vestel) led40127fhdcntd - turns off and on repeatedly

Replace them, you can put one at 20 Ohm.

can i use these ones linked in the pic below or will they blow up?
also i noticed the data sheet says they have a cycle life of 1000 could this by why the original ones popped after 5 years of use with tv being used multiple times every day?

also i forgot to add i got a multimeter across the blown thermistors and the have values of 38.5ohms and 226kohms. the working one has 14.2ohms (around 16c temp in my room) and when i hold it with my fingers its ohms start dropping down.

[lotas]

Re: Bush (Vestel) led40127fhdcntd - turns off and on repeatedly

Replace them, you can put one at 20 Ohm.

[slybunda]

Re: Bush (Vestel) led40127fhdcntd - turns off and on repeatedly

Lotas could this be causing his remote control issues too? or will it be a diffrent fault

i had the batteries out of the remote and this same issue happens, once tv is on it wont power off. im wondering if those thermistors are blown are they responsible for power off the tv and keeping it off?

[vinceroger69]

Re: Bush (Vestel) led40127fhdcntd - turns off and on repeatedly

They (thermistors) are connected in series to the closing contacts of the relay, for a soft start.

Lotas could this be causing his remote control issues too? or will it be a diffrent fault

[slybunda]

Re: Bush (Vestel) led40127fhdcntd - turns off and on repeatedly

They (thermistors) are connected in series to the closing contacts of the relay, for a soft start.

thanks for that info. do i have to use the exact original thermistors that were there or can i use any which are marked as 10ohm 2 amp?

[lotas]

Re: Bush (Vestel) led40127fhdcntd - turns off and on repeatedly

They (thermistors) are connected in series to the closing contacts of the relay, for a soft start.

[slybunda]

Re: Bush (Vestel) led40127fhdcntd - turns off and on repeatedly

iv marked the back of the board here, red box is the thermistors and blue boxes are the legs of the relay. dunno if it helps trace something but the more info the better i guess

[slybunda]

Re: Bush (Vestel) led40127fhdcntd - turns off and on repeatedly

reason is im trying to find ones which i can use instead of ordering the same ones from china which will take a month to arrive.
the shop near me is RS components, which i can get to easily and they have a lot of stuff in stock.

also i believe the website here: https://www.lcsc.com/product-detail/...Y_C211173.html
seems to have different info on the product page compared to the datasheet. webpage says its 3A but datasheet says its 2A so thats where i was getting some confusion from.

there is this one here: https://uk.rs-online.com/web/p/thermistor-ics/1857867
that seems to be close on specs rated at 2A has 30second Thermal cooling time constant but only 1.4w power rating which is less than the original ones 2.3w. capacitance at 240v is also a lot less at 100uf vs the originals 220uf.

im in the United Kingdom so if anyone know what i can get a hold of quickly it would be much appreciated.

[lotas]

Re: Bush (Vestel) led40127fhdcntd - turns off and on repeatedly

Why do you need these tables, buy them or find them on donors with the same markings (SCK 102) and change your burned ones

[slybunda]

Re: Bush (Vestel) led40127fhdcntd - turns off and on repeatedly

https://www.lcsc.com/product-detail/...Y_C211173.html

website above has given me this info on the SCK102
pic attached.

when selecting a thermistor what does the specs need to match? is it just got to be the ohm rating at 25c temp?

what is thermal time constant rating? i see this vary on similar spec thermistors. the SCK102 has 38 seconds and im struggling to find one that matches that exactly, most are 30s or 60s or more?