Power Supply 5W resistor help

[tech2014]

I have a Toshiba tv that is totally dead, no LED at all. I tested the fuses, MOSFETS and rectifiers and nothing found. Also reflowed everything on the heat sinks. I still had no joy. I finally started testing resistors and found an open 1.8 ohm 5W thermal resistor. Does anyone know where I can order these type of resistors. See pic at bottom.

I did have a 2 ohm 10W resistor that I soldered in to test. The power supply powered up and was working. Do these resistors blow on their own, or would something else cause this? I don't want to just replace the part just in case.

[budm]

Re: Power Supply 5W resistor help

Is this from Toshiba power supply? If it is, that resistor is for limiting the inrush current and supposed to be bypassed by the relay contacts, if the relay contacts failed the resistor will get hot and goes open.

[tw2005]

Re: Power Supply 5W resistor help

maybe it copped a surge

datasheet and hopefully find something close

[freakaftr8]

Re: Power Supply 5W resistor help

I repaired one of these before open resistor that you mentioned. You can use a 1.6 to 2 ohm resistor would be okay if you can find one of those as long as the wattage is the same. These usually open from and in Rush current like a power surge or a lightning strike. The one I repaired still working perfect a year and a half later

[stj]

Re: Power Supply 5W resistor help

it should be metal-oxide, NOT wirewound.

[tech2014]

Re: Power Supply 5W resistor help

Would this one work??
http://www.digikey.ca/product-detail....8W-5-ND/18637

[CapLeaker]

Re: Power Supply 5W resistor help

that's wire wound like the original one. It will work fine. If you want and there is space you can put a higher wattage one in it too. Also you could put a bit more Ohms... after all it is just an inrush current limiter to protect the relay.

[budm]

Re: Power Supply 5W resistor help

That resistor limits the inrush current then it is bypassed by the relay so the resistor will no longer have to carry the load current, if the relay failed to bypass the resistor, it will go open circuit again. So if you trace out the two legs of the resistor, each leg of the resistor will go to each contact of the relay which you must verify if it is OK or not.
We still do not know the make or model of this TV. Wire wound is fine and it has to be flame proof type to use since it is for inrush limiter, the current only flow through the resistor for very very short period of time.

[tech2014]

Re: Power Supply 5W resistor help

Its a Toshiba model number 55ZV650U. For testing the relays, can I just remove it from the circuit and make sure they latch when voltage is applied. thanks.

[budm]

Re: Power Supply 5W resistor help

Which resistor is it? There are two of them.
R850 (for bridge rectifier D820)? which is bypassed by relay SR81.
R897, 898 (for bridge D850) is not bypassed by relay due to it is for standby power supply section with smaller filter caps.
http://www.shopjimmy.com/toshiba-750...pply-unit.htm#

Bad relay will still click but it can have bad contact resistance.

[tech2014]

Re: Power Supply 5W resistor help

R850.

[budm]

Re: Power Supply 5W resistor help

OK, if the relay contacts are good, then you should see 0VAC (or very low mVAC range) Voltage drops on that R850 due to the fact that the relay contacts will short out the two legs of the resistor together when the relay is ON. Use 2VAC scale to test.

[budm]

Re: Power Supply 5W resistor help

Similar failure to Toshiba:
https://www.badcaps.net/forum/showth...highlight=SR81

[tech2014]

Re: Power Supply 5W resistor help

ok thanks budm. I will let you know what I find tomorrow.

[budm]

Re: Power Supply 5W resistor help

See post 13.

[tech2014]

Re: Power Supply 5W resistor help

I read post 13. Not sure how to take apart relay without damaging it. It is an Omron 5V relay. I will test it and if it fails I will replace rather the repair.

[tech2014]

Re: Power Supply 5W resistor help

OK I tested the relay by measuring the voltage drop across the relay. The first time I got 0.6V but then every time after that I got close to 0v.

[budm]

Re: Power Supply 5W resistor help

OK I tested the relay by measuring the voltage drop across the relay. The first time I got 0.6V but then every time after that I got close to 0v.

The contacts probably did not make good contact until after a couple actuation.
If the resistor goes bad again then I would replace the relay.

[tech2014]

Re: Power Supply 5W resistor help

ok thanks budm.