Parts ID for Vizio power board model E550i-B2 DPS-167DP-1

[JohnCT]

The short story is that I have to repair board this for someone and it has the typical standby IC failure (LD7913, Schottkey, and Z909 4.7V zener), but someone has harvested some other zeners from the same circuit <sigh> before I got it. Everything else is there.

I know this is a long shot, but has anyone ever documented the zener values in locations Z900, 902, 904, and 907? I assume there's no schematic of this board?

Thanks.

John

[MASTER_TECH_101]

All of them are surge protection diodes, somewhere between 12V and 20V. Circuit should work just fine without them.

[nomoresonys]

In the decent service manuals you will find a complete parts/component list, have not tried looking one up for this model so don't know how available they are.

[MASTER_TECH_101]

All of them are surge protection diodes, somewhere between 12V and 20V. Circuit should work just fine without them.

[JohnCT]

All of them are surge protection diodes, somewhere between 12V and 20V. Circuit should work just fine without them.

Well, to be honest, I never replace the 4.7z because it protects Source pin of the internal mosfet which is almost at ground potential. The way I see it is the only way that pin goes anywhere near zener voltage is if the chip is blown up anyway.

I had considered the possibility the other four missing zeners might serve a similar function as the 4.7 z but then dismissed it figuring one of them at least must be for a reference. Since I have a bunch of those LD7913s in stock and I'm retiring in June anyway, what the heck? Nothing to lose.

So I installed a LD7913 and put my meter on the new Schottkey to monitor the 5V standby and plugged it in. Nothing. I almost quit there but checked from hot ground to D on the chip and there's no B+. Turns out the 4.7 ohm ceramic fuse/resistor is also open, something I had never run across on these boards when the LD7913 blows up. Grabbed one from a donor board and plugged in to find 4.997 volts on the standby...

I let it run all day yesterday and then over night and it's running fine - voltages are right on and the chip is running cool.

Thanks for the suggestion!

John

[thommyX]

LG Thomas