Vizio TV E470VL SMPS Flucuation Output Voltage

[nomoresonys]

Re: Vizio TV E470VL SMPS Flucuation Output Voltage

Yep, that zener is shot, does cap read short now that its off the board? doubtful but dont hurt to make sure.

[nomoresonys]

Re: Vizio TV E470VL SMPS Flucuation Output Voltage

best to practice soldering and desoldering on just any old scrap of pcb board, theyre in most electronics, so just about any old nonworking device, tear apart and practice on the boards.

[nomoresonys]

Re: Vizio TV E470VL SMPS Flucuation Output Voltage

zener has tiny writing on it telling its value, check it under magnification, cap is probably ok, make sure its not still reading short in diode mode, then check it in ohm mode. check across where they come off the board and make sure the short is gone.

[dholley]

Re: Vizio TV E470VL SMPS Flucuation Output Voltage

At the the moment I think the Cap is covered with alloy, because I don't see the part anywhere else!!! and with that testing is not possible. Any idea about a replacement part for the zener and cap? Are those types of capacitors polarized?

[dholley]

Re: Vizio TV E470VL SMPS Flucuation Output Voltage

our messages occurred at the same time so I have you answer about the zener. Can you tell me if the cap is polarized?

[nomoresonys]

Re: Vizio TV E470VL SMPS Flucuation Output Voltage

theyre nonpolorized, pretty sure you can use a cap thats the same size, just make sure its a cap, zener value is on it tiny writing.

[dholley]

Re: Vizio TV E470VL SMPS Flucuation Output Voltage

thank you!

[dholley]

Re: Vizio TV E470VL SMPS Flucuation Output Voltage

The ZD104 has 18 ZD written, so is that an 18 volt zener diode? I found cap c107 buried in some alloy, it is about the 1/4 the size of a pencil tip. If I did it correctly is measures about 66 pf, does that sound right? It was not short.

[nomoresonys]

Re: Vizio TV E470VL SMPS Flucuation Output Voltage

yes 18 volts, measure the cap in ohm mode, what do you get?

[nomoresonys]

Re: Vizio TV E470VL SMPS Flucuation Output Voltage

did you measure across the pads the cap came off of and the holes the zener came out of, no more shorts there right?

[nomoresonys]

Re: Vizio TV E470VL SMPS Flucuation Output Voltage

as long as its not shorted and isnt reading very low ohms, i would put it back in with the new zener and see what you get.

[dskall]

Re: Vizio TV E470VL SMPS Flucuation Output Voltage

I think you should have a diode and and a 10uf cap in the circuit also.

[dholley]

Re: Vizio TV E470VL SMPS Flucuation Output Voltage

I think you should have a diode and and a 10uf cap in the circuit also.

As of yet I don't see a diode on Vcc Pin 3, I don't see a 10uf cap, but there is a 47uf. I have tested that cap I think it is approximately 43uf

[dholley]

Re: Vizio TV E470VL SMPS Flucuation Output Voltage

yes 18 volts, measure the cap in ohm mode, what do you get?

The cap charges up very quickly in ohm mode, so there is not really a measurement for before it goes to OL

[dholley]

Re: Vizio TV E470VL SMPS Flucuation Output Voltage

did you measure across the pads the cap came off of and the holes the zener came out of, no more shorts there right?

Correct

[dholley]

Re: Vizio TV E470VL SMPS Flucuation Output Voltage

as long as its not shorted and isnt reading very low ohms, i would put it back in with the new zener and see what you get.

Ok

[nomoresonys]

Re: Vizio TV E470VL SMPS Flucuation Output Voltage

The cap charges up very quickly in ohm mode, so there is not really a measurement for before it goes to OL

I think the reason is you need to set meter higher in ohm mode to get a steady reading, its probably ok.

[dholley]

Re: Vizio TV E470VL SMPS Flucuation Output Voltage

When installing the zener diode does the dot / bar go to the pointed arrow side ?

I lost the capacitor, I think it is 66 pf, how critical is it match the original cap?

[nomoresonys]

Re: Vizio TV E470VL SMPS Flucuation Output Voltage

Yes the black stripe to bar side, I think you will be ok with a cap the same size, look at one of your other zeners to verify orientation.

[dholley]

Re: Vizio TV E470VL SMPS Flucuation Output Voltage

It is a head scratcher! I replaced the zener diode and the cap. There is approximately 2.2 volts at Vcc which is better than zero I guess. But still no output voltage. With the power off and multimeter in diode mode Vcc to ground shows about 1.47 volts, before changing the zener I think it was approximately.02 volts.

I sprayed the board front and back with freeze spray with power on but did not find any obvious shorts.

Any suggestions?