Vizio 500I-B1 no standby power

[thezboe]

Hello all,

I've inherited a non-working Vizio 500I-B1 TV that someone else has tried to fix. When I opened it, the top of the IC9301 chip had blown off. I ordered a few more and replaced it, but haven't made really any other progress.

The part number on the power supply board is 715G6100-P05-003-002H.

I don't get any readings on the standby connector for the 5, 12, or 24v rails.

This other post with a similar looking IC9301 chip said to make sure that the 'fusible resistor 9301' wasn't bad as well.

I've found a JR9301 (what does JR mean in this instance?), which is what I assume that poster was talking about. When measured, it has almost no resistance across it but I'm not sure if it should when the board is powered off since at least one other component labeled "JR" also didn't measure any resistance across it. Should this measure resistance at all times?

Any help is much appreciated. Thank you!

[budm]

Re: Vizio 500I-B1 no standby power

JR = JUMPER (I.E. Jumper wire, 0 Ohm jumper resistor).
R = Resistor, you need to check Fusible Resistor R9301.

[R_J]

Re: Vizio 500I-B1 no standby power

I see JR9301 (0Ω) is located on the trace side of the board
If IC9301 is blown, R9301 fuseable resistor will be open and it needs to be replaced.
Here is the location of R9301

[budm]

Re: Vizio 500I-B1 no standby power

I think OP is referring to the 0 Ohm jumper resistor JR9301 on the link he gave.
https://www.badcaps.net/forum/attach...5&d=1502901155

[R_J]

Re: Vizio 500I-B1 no standby power

Ok, thanks I did'nt see that JR9301 on the trace side , I corrected my post to avoid confusion.

[thezboe]

Re: Vizio 500I-B1 no standby power

Ah, thank you for pointing that out!
I'm confused as to the purpose of a 0 ohm resistor. why didn't they just connect the traces? perhaps for different revs of the board that may not use 0 ohms there?

Also, measured the resistance across that fusible resistor, and it's 0 ohms also. So I'm assuming that's blown. Anyone happen to know the part number for that guy?

[R_J]

Re: Vizio 500I-B1 no standby power

R9301 is a 0.1Ω 1watt fusible resistor, so your's checks ok.

[thezboe]

Re: Vizio 500I-B1 no standby power

/facepalm

A blown resistor would read infinite resistance wouldn't it.

[R_J]

Re: Vizio 500I-B1 no standby power

Resistors usually fail open, yes. If R9301 checks like a short is is ok, Usually when the ic shorts it blows the resistor but sometimes the ic shorts and blows itself open so the resistor does'nt open, R9301 is basically just a fuse in the supply voltage line to the ic.

[thezboe]

Re: Vizio 500I-B1 no standby power

Okay, thanks for that. Do you have any pointers as to where to look next? Perhaps I soldered IC9301 badly. Do you know what those voltages should be?

[R_J]

Re: Vizio 500I-B1 no standby power

This ic is for the +5 volts STANDBY only, Check for it at J9307
I Can't see your soldering from here, hold it closer to the monitor, or maybe upload a picture .
If you don't have the standby voltage you need to check the voltage on ic9301 (part number?)
Check the voltage on the primary side using BD9902 negative lead (or J9905) for your meter ground and measure the DC voltage on R9301, it should be 160vdc

[thezboe]

Re: Vizio 500I-B1 no standby power

J9307 seems to have almost no voltage. Reading 0.03V but distinctively not 0.

The part number that I replaced IC9301 with is STR-A6069H. Ordered from Digikey.

I checked the voltage between J9905 and FB9301 (R9301) and got 167V, so that's something.

Here is a picture of my terrible solder job. The pads almost seem to be gone from the previous person that attempted a repair, so I may have to scratch away to get some copper. Only if necessary of course.

[R_J]

Re: Vizio 500I-B1 no standby power

With no power applied, check the resistance of R9311/12 (should be about 0.6Ω) then check ZD9301 in diode test.
Apply power and using hot ground (bridge rectifier -) check that you have 160 volts on pin7,8 of ic9301, then check the voltages on the other pins and post them.
Check that the ic pins are actually making contact wih the circuit, pin5 does not look good.

Be carefull this is the hot side of the power supply.

[thezboe]

Re: Vizio 500I-B1 no standby power

Those resistors are reading about 1.3 ohms for me.
This model doesn't have any component in the place for ZD9301.

I am getting 164V on pin 7,8 of IC9301.
I think I may have found a problem and you were correct about pin 5!
If I put the lead on the pin, i get ~5.5V, but if I put it on the test pad just a millimeter away, I get around 0. So my soldering job is bad here, but the pad is gone. I think I will just solder that pin straight to the test pad that is just down the trace a very small distance away.

[thezboe]

Re: Vizio 500I-B1 no standby power

So I soldered that, now I get ~10V from pin 5 to that entire trace so it seems to be connected now, but the voltage is more than it was before.

Checking J9307 again initially gave me ~1V, but then it just steadily declines while it's reading.

[R_J]

Re: Vizio 500I-B1 no standby power

How do I find out the other voltages on the other pins? 10v on pin 5 comes from the startup cell within the ic itself
What is the voltage across C9305 and C9308? These caps could also be bad.
Check the resistance of the optocoupler on the primary side, since the ic blew up it may have damaged the optocoupler

[thezboe]

Re: Vizio 500I-B1 no standby power

C9308 is 9.6V
C9305 started out near 9.6V but constantly falls as I measure.

Pin 2 in IC9301 is 2V. All the other pins are 0.

There are 2 octocouplers in that area. 9302 seems to read infinite resistance in both directions on the primary side. So that doesn't sound good.

[thezboe]

Re: Vizio 500I-B1 no standby power

Though, I will say that I'm not getting any voltage differential across the pins of IC9302 on the primary side when the unit is powered.

[thezboe]

Re: Vizio 500I-B1 no standby power

removed.

[R_J]

Re: Vizio 500I-B1 no standby power

If you don't have another optocpupler, try swapping the two around to see if you get +5v standby, another thing to check are the resistors R9309, R9313, R9316 & R9318. follow pin2 to J9303,J9802,J9134 to the resistors, They are 1.5megΩ so they may be hard to check. You could also check the voltage on D9301 (using hot ground) and then check the voltage on each resistor.