Re: Vizio 500I-B1 no standby power
Does IC9101 provide the 24V or the 12V rail? I see the sort of "voltage divider" with the transformers. The 12V rail is coming out okay, but the 24V rail is not correct.
Every now and then I can get the TV to power on and work perfectly. When it happened the last time, the 24V rail was reading 15V! So I'm not sure what the difference is when the TV powers up and when it doesn't currently since the power rails seem to be the same in either case.
thezboe
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Last Activity: 05-26-2020, 06:04 PM
Joined: 09-05-2019
Location: Gilbert
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Re: Vizio 500I-B1 no standby power
That didn't do anything for me. No reaction at all from the power board, only the 5V standby was on. No 12V or reading on the 24V line. so it seems to not be signalling to the power supply to "turn on".
When the board powers up with the cable plugged in, the voltage to PS_ON, ON_OFF both read 3.3V thereabouts. But the DIM pin reads like 0.05V.Leave a comment:
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Re: Vizio 500I-B1 no standby power
I will try that tonight.
I also was looking at the output voltages when this is happening. The 5V and 12V rails are good, but the 24V rail is reading something like 15.6V. It seems pretty rock solid at that voltage, so it doesn't seem like a feedback loop issue to me. Maybe a bad cap on the cold side?Leave a comment:
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Re: Vizio 500I-B1 no standby power
So I'm looking into this set again after a while of just letting it sit. I opened it up and just figured I'd power it up just to see and it powered on fine! Left it going for the night and turned it off a while ago. Tried to turn it back on and it's displaying the same issue. Backlights flicker on real quick and then back off. The sound works fine however. Any ideas what it could be?Leave a comment:
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Re: Vizio 500I-B1 no standby power
Well the TV worked for one night and now it's kaput again.
I have standby voltage, and I can turn it on and the light goes solid but no backlights. I am getting like 1.8 volts to both the 12v and 24V(18V?) pins. The transistor labeled IC9103 was the pain point that I fixed that made it started working last time. The solder job is still good so it must be something else.
Let's try this again, shall we?
What do the R/A/K letters mean on the labeling for the terminals of IC9301?Leave a comment:
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Re: Vizio 500I-B1 no standby power
I ran across a video on Youtube that gave a great description of all the parts of a switching mode power supply. The key was that if you're voltages off the dual diodes are low, that usually means that something is happening with the feedback circuit that goes through the optocoupler back to the primary side. I figured it was the opto itself, but it tested good so I started tracing it all the way back to the transformer. Honestly, I should've checked that solder job sooner since the previous person that tried to fix it really messed up everything...Last edited by thezboe; 10-25-2019, 06:29 PM.Leave a comment:
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Re: Vizio 500I-B1 no standby power
It works! I had a bad solder joint on the transistor that's part of the feedback loop to IC9101.Leave a comment:
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Re: Vizio 500I-B1 no standby power
I've replaced IC9101 and it appears to still exhibit the same behavior.
I'm at a loss now.Leave a comment:
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Re: Vizio 500I-B1 no standby power
I've ordered another IC9101 (LCS703LG). Unfortunately it's terribly hard to read if the PWM coming off of it to the transformers is correct or not.
On another note, can someone tell me the purpose of the dual schottky diodes D9103 and D9104. Both anodes are connected together on the same trace. I even see the same sort of magic laid out in the spec page for IC9101, but it just doesn't make any sense. My guess is to split the current and heat between the two diodes? But they are on the same chip?Leave a comment:
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Re: Vizio 500I-B1 no standby power
EDIT: found them. checking.
My meter reads 0.1 for both diodes going from both anodes to common cathode. Interestingly, it also reads continuity with the leads reversed (although with a greater reading on the meter).Last edited by thezboe; 10-16-2019, 03:17 PM.Leave a comment:
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Re: Vizio 500I-B1 no standby power
When powered on, pin #1 is at 13.75VLeave a comment:
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Re: Vizio 500I-B1 no standby power
R9140 reads between 0.3 and 0.4 ohms....Leave a comment:
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Re: Vizio 500I-B1 no standby power
I have checked all that I could see and they are all good. I may have missed some on the bottom side since they are small....Leave a comment:
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Re: Vizio 500I-B1 no standby power
Voltage on those caps goes from 167V to 392V when turned on. The standby light turns on when I plug it in, but then fades away after about 10 seconds. Not sure if that is nominal.Leave a comment:
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Re: Vizio 500I-B1 no standby power
The 12V and 24V rails are reading 7V and 9V respectively.
When the power button is hit ps_on goes from 0.4V to 3V or so. So this seems like a power supply issue and not a logic board issue.
The way the other threads have gone, this seems like an IC9101 issue?Leave a comment:
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Re: Vizio 500I-B1 no standby power
UPDATE: Some solder connections weren't good enough to have continuity. Some of these solder pads are just destroyed from the previous person to try to fix it.
I now have standby!!! The light is on. I hit the power on button and the lights flicker and go off really quick. Any tips for this new development?
I can hear buzzing on the power board coming from either IC9101 or T9301. It is really fast right when I hit the power button and then it slows down after the backlights flash on and off.Leave a comment:
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Re: Vizio 500I-B1 no standby power
I've replaced IC9302, but nothing has changed. I get about 0.9V across the primary side of that optocoupler, but I assume that's less that the bias on the LED to get anything out the other side.Leave a comment:
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Re: Vizio 500I-B1 no standby power
removed.Leave a comment:
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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.Last edited by thezboe; 09-13-2019, 04:55 PM.Leave a comment:
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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.Leave a comment:
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