Blown heated blanker controller. Trying to figure out these smd resistors

[Widget]

Hello,

We have one of those heated throw blankets you plug into AC power. The other day it went *bzzzbzzzbbzz... pop*, so I opened it up to find what appears to be two resistors gone *poof*. (R7 & R14 in picture)

luckily, we have a second blanker with what appears to be identical controller, so I opened it up to take a picture

According to the good controller PCB, R7 = 9531, & R14 = 103

Online SMD resistor calculator says

R7 - 9531 = 95.3kohm
R14 - 103 = 10kohm

Is this correct? Would all I need is a 10k ohm & a 9.53k ohm? I had a google but there seems to be many types with many with different tolerances. Any suggestions on which ones I should choose?

[stj]

first you need to find out what has shorted to make them burn.
start by checking diodes and ceramic caps

[redwire]

Resistors never fail and burn up of their own accord. Something happened to overload them.
If it was a mains transient, lightning that arced over them, then whatever is downstream next is surely dead. They seem to go from control button (or whatever blanket 3rd pin is for) to R14 to MCU... that is surely toast.
Does it power up? LED display on?

[Widget]

first you need to find out what has shorted to make them burn.
start by checking diodes and ceramic caps

The track they're on is connected to an unknown IC & leads to the main input for the throw-blanket. The only other cap I see is linked to R14 resistor but the capacitor has no value written on it. The blanket/controller that's good is still under warranty & desoldering the cap to check value I can't do. Can these caps be checked in circuit?

Resistors never fail and burn up of their own accord. Something happened to overload them.
If it was a mains transient, lightning that arced over them, then whatever is downstream next is surely dead. They seem to go from control button (or whatever blanket 3rd pin is for) to R14 to MCU... that is surely toast.
Does it power up? LED display on?

Unsure. Was just sitting there & poof. No lightning, no known electricity spikes. Surprisingly I found a review on Amazon with the same controller & the same issue https://www.amazon.co.uk/Homefront-E.../dp/B001IRYFJG. Could it be a design fault?

No power, no LED. I'll have to plug it in and take some reading maybe.

[stj]

picture of the other side?
i dont see a triac or other switching device - maybe it's the chip you mentioned.
also cant overlook a short in the cable to the blanket

[redwire]

OP is two timin' he went to that other forum https://www.eevblog.com/forum/beginn...smd-resistors/
good luck with the dorks

[stj]

they wont show any mercy at eev even though 75% of them are idiots!

[Widget]

picture of the other side?
i dont see a triac or other switching device - maybe it's the chip you mentioned.
also cant overlook a short in the cable to the blanket

Sorry for the delay in response. I've attached two images showing each side. I'm not sure what a 'triac' is, I was hoping for it to be a simple resistor replacement lol, guess I'll have to weigh up trying to fix or whether it's best to scrap it. I'll have a look for some shorts, but in regards to the chip, if the chip can't be identified then I won't know what value to measure at the pin(s), therefor it would make it near impossible to repair, no?

OP is two timin' he went to that other forum https://www.eevblog.com/forum/beginn...smd-resistors/
good luck with the dorks

they wont show any mercy at eev even though 75% of them are idiots!

Haha, technically I posted on eevblog first before coming over here, but I like to post of both due to different members, hopefully get a larger response to questions.

[stj]

so it doesnt have a thermostatic switch, just a teperature disply/timer?

[Widget]

so it doesnt have a thermostatic switch, just a teperature disply/timer?

Not sure to be honest. I only know of the on/off switch & buttons to control temperature & timer (s2 & s3).

[redwire]

OP said it was likely a short between mains and the thermistor, he binned it.

[Widget]

OP said it was likely a short between mains and the thermistor, he binned it.

No, Kurets said that, not me (op) lol. but yes, I'll probably have to bin it.

[stj]

i cant see any mains switching devices,
i'm wondering if the numbers are just a display rather than a control.
and if both fuses are good it may just be a shorted display chip
it looks like it has a big switch so maybe it just has full power and half power (half wave rectified) to the heater

[petehall347]

here is a different repair on the same controller . https://jestineyong.com/homemaker-el...ow-rug-repair/
and here is a pic of how it looks on the front .

[petehall347]

am guessing the middle contacts black and white wires go to a thermistor in the blanket .

[Widget]

i cant see any mains switching devices,
i'm wondering if the numbers are just a display rather than a control.
and if both fuses are good it may just be a shorted display chip
it looks like it has a big switch so maybe it just has full power and half power (half wave rectified) to the heater

Oh, I didn't see/test the white (ceramic) fuse (F1), iirc the glass fuse (F2) tested ok.

The big (0-1) switch is on/off. The temperature & timer go up to 9 I think via the soft-press gray buttons

here is a different repair on the same controller . https://jestineyong.com/homemaker-el...ow-rug-repair/
and here is a pic of how it looks on the front .

Saw that one, pitty it wasn't the same repair I need lol.

am guessing the middle contacts black and white wires go to a thermistor in the blanket .

I'm not sure how the wires in the blanket work. There's 4 wires that run into the blanket but none seem to be linked to each when I did a cont test.

[petehall347]

f1 looks like a thermal fuse
the wonky display might not be helping things

[petehall347]

see what resistance between black and white and blue and brown .

[CG2]

Check the resistances of the blanket and compare it with the good one before you turn to the controller. Some blankets have a sense wire in addition to the heating one, and if that is damaged the controller responds by effectively committing suicide. The blown resistors may be a symptom of a dead blanket.

[stj]

are there any more components under those elevated displays?