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Old 01-20-2022, 09:14 PM   #21
dholley
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Default Re: Vizio TV SMPS Flucuation Output Voltage

Regarding R102, testing on side closest to filter capacitors voltage is 169, testing on side closest to IC voltage fluctuates between 79 and 112 volts . Testing at pin 3 of IC which I think is VCC voltage fluctuates between 9 and 11 volts
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Old 01-20-2022, 09:19 PM   #22
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Default Re: Vizio TV SMPS Flucuation Output Voltage

what about the voltage on D102?
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Old 01-20-2022, 09:24 PM   #23
dholley
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Default Re: Vizio TV SMPS Flucuation Output Voltage

D102 testing bar / striped side fluctuates between 8 and 9 volts
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Old 01-20-2022, 09:31 PM   #24
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Default Re: Vizio TV SMPS Flucuation Output Voltage

Quote:
Originally Posted by dholley View Post
I just measured, there is NO 5 volt or 12 output. The 5 volt was fluctuating from 3 to 4 volts but is now 0 volts. The big capacitors were at 167 volts they are now at 171 volts. I donít know what happened.
Are you getting anything on the 5 volt line or is it still 0 volts? If it is 0 volts I suspect the u101 is bad and not switching at all.
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Old 01-20-2022, 09:34 PM   #25
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Default Re: Vizio TV SMPS Flucuation Output Voltage

It is now fluctuating around 4 volts
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Old 01-20-2022, 09:41 PM   #26
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Default Re: Vizio TV SMPS Flucuation Output Voltage

I appreciate your help RJ. I’m signing off for tonight, but will be happy to provide any additional information in the morning. Thank you!!!
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Old 01-20-2022, 09:43 PM   #27
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Default Re: Vizio TV SMPS Flucuation Output Voltage

If you are getting around 4v on the secondary, you should be getting around 18v on D102. Check that feedback winding on the transformer, check R105, Check D102. If these parts are good then either C104 is bad and not charging

That feedback circuit also supplies Q101 collector which is a regulator/switch that supplies vcc2 (on its emitter) to the pfc ic U601

Last edited by R_J; 01-20-2022 at 10:01 PM..
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Old 01-21-2022, 11:16 AM   #28
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Default Re: Vizio TV E470VL SMPS Flucuation Output Voltage

1. Can you tell me how to test the feedback winding on the transformer?
2. R105 is 10.01 ohms tested in circuit
3. D102 is fluctuating between 8 - 9 volts
4. C104 - with my ESR meter is says it is a good cap with low esr
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Old 01-21-2022, 11:29 AM   #29
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Default Re: Vizio TV E470VL SMPS Flucuation Output Voltage

Just check the resistance of the winding, it should check around 1Ω. D102 is a diode, use diode test on your meter to check it. The ic shuts down with only 8 volts of vcc
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Old 01-21-2022, 11:52 AM   #30
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Default Re: Vizio TV E470VL SMPS Flucuation Output Voltage

In measuring the transformer from the bottom side of the board, hot side, I put my lead at the end of the transformer leg nearest the IC and put the other lead on the next closest leg, 0.50 ohms, i used the same method on the opposite end 1.0 ohm.

D102 - with the diode test of the multi meter, OL one way and 0.536 volt the other
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Old 01-21-2022, 12:35 PM   #31
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Default Re: Vizio TV E470VL SMPS Flucuation Output Voltage

The diode check ok, I just had a closer look at the top third picture and C114 looks damaged? or is that black from something else?
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Old 01-21-2022, 12:46 PM   #32
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Default Re: Vizio TV E470VL SMPS Flucuation Output Voltage

Oh my gosh RJ, GREAT JOB!!!!!!!!!!! It is indeed damaged!!!
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Old 01-21-2022, 12:53 PM   #33
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Default Re: Vizio TV E470VL SMPS Flucuation Output Voltage

Pictured attached
Attached Images
File Type: jpg Damaged Capacitor.jpg (599.0 KB, 17 views)
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Old 01-21-2022, 01:01 PM   #34
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Default Re: Vizio TV E470VL SMPS Flucuation Output Voltage

Is the capacity marked on the other side? if it is it is likely a 1kv cap, replace it with a 2kv is recommended
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Old 01-21-2022, 01:20 PM   #35
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Default Re: Vizio TV E470VL SMPS Flucuation Output Voltage

there is no marking on the other side, but it looks like C106 which is near the big filter cap, next to the red transformer. C106 is a 1kv

It looks like, C610 not C106

C610 is 101k, 1KV. Do you have a replacement recommendation and they are non-polarized correct?

Last edited by dholley; 01-21-2022 at 01:36 PM.. Reason: Correct Cap reference
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Old 01-21-2022, 01:46 PM   #36
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Default Re: Vizio TV E470VL SMPS Flucuation Output Voltage

have another 101k 1kv on another board, do you think it would be ok to install it and see if that fixes this boad?
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Old 01-21-2022, 02:18 PM   #37
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Default Re: Vizio TV E470VL SMPS Flucuation Output Voltage

the Damaged cap measured approximately 90 PF, if it is a 101k that is pretty close to the right value
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Old 01-21-2022, 02:37 PM   #38
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Default Re: Vizio TV E470VL SMPS Flucuation Output Voltage

I replaced the cap with one from another board. It measured approximately 115 PF. Powered up the board and there is still fluctuation at the output pin and at vcc
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Old 01-21-2022, 04:58 PM   #39
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Default Re: Vizio TV SMPS Flucuation Output Voltage

Quote:
Originally Posted by nomoresonys View Post
Touch up some of those solder joints.
Did you touch up those suspicious joints? just in case you missed the post.
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Old 01-21-2022, 05:47 PM   #40
dholley
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Default Re: Vizio TV E470VL SMPS Flucuation Output Voltage

I re-soldered a couple, can you tell me where exactly that needed attention?
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