Vizio VO32L, another one with bad VRs? Need help figuring out the resistors too

[TechShui]

Re: Vizio VO32L, another one with bad VRs? Need help figuring out the resistors too

Sorry for long wait between responses, i do agree that the expected output voltage is 1.8v but why does a higher 2.25 v not allow the set to power on?

[tom66]

Re: Vizio VO32L, another one with bad VRs? Need help figuring out the resistors too

Because the chip is designed to operate on 1.8V. It might malfunction when driven too high.

At work we had ARM CPU with a 1.2V core operate happily at 5V (by accident), but it ran extremely hot and crashed often. We've also had ones not operate at 1.5V, with their rated operating voltage of 1.2V.

[TechShui]

Re: Vizio VO32L, another one with bad VRs? Need help figuring out the resistors too

Tom, thanks for your insight, i appreciate it
One thing that still leaves me scratching my head:
Original regulator is A1117, datasheet here
I replaced with a spare G1117 that i have, datasheet for that shows the specs as identical*

From this can we conclude that one of the resistors is not correct? And therefore the produces a higher voltage than intended?

*unless i missed something

[TechShui]

Re: Vizio VO32L, another one with bad VRs? Need help figuring out the resistors too

A few more general questions.

Can someone tell me what the difference is between Low Dropout (LDO) regulators and Very Low Dropout?

I have another voltage regulator that I'm considering placing as u20, in the hopes of getting the correct 1.8v.

This one is a FIXED regulator, 1.8v, and labeled SC1565
Here's the datasheet:
http://www.alldatasheet.com/datashee...CH/SC1565.html

The amperage is also different, 1.5A instead of the 1A that the 1117s have. but I'm assuming the cpu will only draw as much current as it needs, so it should be safe the use the higher amp device, right?

My second question is this:

Two things need to happen for the fixed voltage regulator to work

1. Both resistors (R35 and R36) need to be removed?
2. the connections (pads) where they are need to be bridged?

Is this correct?

Here is a link to the photo where u20 and the resistors are.
https://www.badcaps.net/forum/attach...4&d=1374772483

[tom66]

Re: Vizio VO32L, another one with bad VRs? Need help figuring out the resistors too

A few more general questions.

Can someone tell me what the difference is between Low Dropout (LDO) regulators and Very Low Dropout?

Marketing.

I have another voltage regulator that I'm considering placing as u20, in the hopes of getting the correct 1.8v.

If you connect ADJ to GND and removed the top resistor, that would probably work.

The amperage is also different, 1.5A instead of the 1A that the 1117s have. but I'm assuming the cpu will only draw as much current as it needs, so it should be safe the use the higher amp device, right?

Current rating is a maximum -- also dictated by thermal performance -- and not something you have to match (just equal or more than is usually OK.)

[TechShui]

Re: Vizio VO32L, another one with bad VRs? Need help figuring out the resistors too

Marketing.

I thought so

If you connect ADJ to GND and removed the top resistor, that would probably work.

You mean I only need to remove R36 and bridge the pads? (see photo please, https://www.badcaps.net/forum/attach...4&d=1374772483 )

Current rating is a maximum -- also dictated by thermal performance -- and not something you have to match (just equal or more than is usually OK.)

Thanks!

[tom66]

Re: Vizio VO32L, another one with bad VRs? Need help figuring out the resistors too

R36 remove and replace with solder bridge. Leave other pad open. Solder in new regulator.