Vizio E401i-A2 No Voltages out of main Power Supply

[david.aaron.long]

Hello BadCaps community. I'm not sure if I've ever posted here, but I've been using the pages of troubleshooting in these forums for years. Thank you for your insight. You've taught me a lot and saved me hundreds if not thousands of dollars.

I have a Vizio E401i-A2 that I was asked to take a look at for a friend. When the set is plugged in, I do not see any standby light.

I've fixed a number of sets and have checked what I would consider to be the most common failures that I see. The main fuse on the power board tested short in Diode mode, the caps all looked good on the power board, and none of the FETS or Schottky diodes tested short in diode mode. The power doesn't appear to be making it to the low voltage side of the power board. I'm reading 0v on every pin of CN201 (to main board) with the meter in DC Volts, measuring with chassis ground and each pin. I didn't see a specific pin specified as standby, so I'm wondering if this is possibly one of those sets that doesn't have a standby voltage.

I've attached some pictures of the Power board and the main board. Any further direction you can give me would be much appreciated. Thank you

[CapLeaker]

Re: Vizio E401i-A2 No Voltages out of main Power Supply

check and see if D210 on the back of the PSU is shorted? Measure the resistance between 3.3V and GND. If that doesn't yield anything, go to the primary side of the PSU and check D501, D502, ZD503, D602, D601, R501 and measure the DCV on IC501 to see if it is getting any power.

[dskall]

Re: Vizio E401i-A2 No Voltages out of main Power Supply

What dcv are you getting across main 68uf cap?

[david.aaron.long]

Re: Vizio E401i-A2 No Voltages out of main Power Supply

check and see if D210 on the back of the PSU is shorted? Measure the resistance between 3.3V and GND. If that doesn't yield anything, go to the primary side of the PSU and check D501, D502, ZD503, D602, D601, R501 and measure the DCV on IC501 to see if it is getting any power.

D210 isn't beeping in diode mode. However, it did register voltage in both directions. Upon pulling it out of circuit, it only registered in one direction again.

I did measure a voltage of .170V on the PS-ON pin. Sorry I didn't catch that before.

Resistance between 3.3V and GND is 500 ohms. Since these gave resistance, do I need to go ahead with D501 - IC501 as listed in your instructions?

[david.aaron.long]

Re: Vizio E401i-A2 No Voltages out of main Power Supply

What dcv are you getting across main 68uf cap?

When I tried to measure DCV across the main cap it sparked and blew the fuse. Am I not supposed to put negative to negative and positive to positive? I replaced the fuse but am hesitant to try that measurement again. Thanks for your help

[david.aaron.long]

Re: Vizio E401i-A2 No Voltages out of main Power Supply

I got the courage back up to measure the voltage across the main cap. It read 166.5V which is about what I'm getting from the DC out on the Bridge rectifier

[dick_barton]

Re: Vizio E401i-A2 No Voltages out of main Power Supply

D213 looks as though it has solder between all 3 pins and therefore shorted. Many of the joints could do with fresh flux being applied and perhaps a hotter iron to clean the joints up.

[CapLeaker]

Re: Vizio E401i-A2 No Voltages out of main Power Supply

When I tried to measure DCV across the main cap it sparked and blew the fuse. Am I not supposed to put negative to negative and positive to positive? I replaced the fuse but am hesitant to try that measurement again. Thanks for your help

thats because the DMM was on the wrong setting. With there not being a short between GND and the 3.3V pin, you'd have to move the troubleshooting over to the primary side of the PSU. Find out if the IC get's proper Vcc first. You may have to pull the datasheet to see what pin is Vcc. You know, that there is rectified AC available on the main filter cap, but does it reach the STBY IC? Be careful in the primary serction of the PSU. If you measure anything DCV on the primary, the negative lead of the DMM goes on the negative of the main filter capacitor.

[budwich]

Re: Vizio E401i-A2 No Voltages out of main Power Supply

From the "storyline", it appears that you had the meter on resistance measurement and had the board powered to do a voltage measurement. :-( Hopefully you didn't take out your resistance measurement capability on your meter (should be fuse protected). :-(
scary test "technique".

[david.aaron.long]

Re: Vizio E401i-A2 No Voltages out of main Power Supply

Thank you for the additional help and instructions. I think that in my apprehension the probe slipped off of the negative side of the cap and touched something else. I should have clarified that the fuse I blew was the fuse on the power supply, not the fuse on the meter.

I think you are right about IC501 possibly being the culprit. There is a noticeable piece of material missing from it.

It is labeled TNY174, and the rest is blown off. I'm assuming based on a google search that it is TNY174PN. I'm not sure what the rules are as far as attaching datasheets or linking to external sites, so I won't do that here until given permission to do so.

When I look at the datasheet, I don't see a Vcc labeled. As you said, on the primary side I should put the negative lead of my meter to the negative lead of the primary cap. Which pin should I be putting the positive lead on according to that datasheet? S pins, EN pin, BP/M Pin, or D pin?

Thanks and apologies for my lack of experience. I truly want to improve in my troubleshooting abilities, so I decided I needed to take the plunge and start asking for help.

I'm ordering a replacement given the damage shown in the attached picture. I'll report as soon as it's reinstalled.

I have also cleaned up the solder joints around D213 and made sure there were no shorts.

While I have your expert input and am waiting for the new part to arrive. I've always hesitated to buy a nice iron, because I don't want to waste the money on something that isn't adequate. Do you have any recommendations? My wife is looking for Christmas ideas... Thanks!

[CapLeaker]

Re: Vizio E401i-A2 No Voltages out of main Power Supply

Hakko or Weller temperature controlled soldering stations. These are rather expensive, but folks come to me to get things fixed, which the little 25w iron couldn't do. Don't get the Weller with the red handle from the department store. Those are junk. So get something with at least 40w or better.

I have to be really careful with that autocorrect on my IPad, when I am on the go. It likes to correct Ven to Vcc and such. If there is no voltage on the enable pin, then it will stop switching. Then there is overvoltage protection to consider too. There is a diode on the drain pin, check that. Other than that, I can't really see all the goodies until I am home again sitting on my computer. I had a look at the IC, but again... on the little screen I can't see it well enough.

[david.aaron.long]

Re: Vizio E401i-A2 No Voltages out of main Power Supply

Thank you so much for the advice. I ordered a Hakko temperature controlled unit in a set with some additional accessories. In the meantime, I received the replacement IC501, and bam, the TV fired right up. Thanks so much for the help guys. Another TV saved from the dump...