Acer GD235HZ Not powering on

[knoxrebel]

hey guys, back again with another one that has me stumped. No power light, will not power on. Also can someone point me to an explanation of how Standby voltage switching works.

Board is getting power.
Bridge Rectifier -- checked.
Main Cap -- 169v -- checked
All diode and resistors pass visual inspection.

Power connector to video board, 5v is present nothing on STB or other pins.

[budm]

Re: Acer GD235HZ Not powering on

The power supply is an always on power supply , since you are getting the 5VDC to run the main board so it means the power supply is workinG.
You need to check the DCV on the main/logic board.
There should be some Voltage regulators ICs on the main board.
Pictures of the main board?

[knoxrebel]

Re: Acer GD235HZ Not powering on

Thanks for the reply. Should have known better, but I was pretty sure that we had a power supply issue.

[knoxrebel]

Re: Acer GD235HZ Not powering on

Update: Thanks for the direction. We had a bad 3.3v regulator I202 which was pulling down the 5v rail to the logic board.

Does this component have to be replaced or can a wire be run from I203 which is also 3.3 regulator?

[budm]

Re: Acer GD235HZ Not powering on

Probably will be too much to use one regulator to supply all the required 3.3V.
BTW, what do you mean by loading down the 5V supply, does the input pin or output pin of I202 show very low resistance?

[knoxrebel]

Re: Acer GD235HZ Not powering on

Tested input pin and it only measured ~2v and no output. After removing part the input pin now shows 5v. Replaced with salvaged part for testing and it works properly.

[budm]

Re: Acer GD235HZ Not powering on

Tested input pin and it only measured ~2v and no output. After removing part the input pin now shows 5v. Replaced with salvaged part for testing and it works properly.

You found the problem for sure then.

[knoxrebel]

Re: Acer GD235HZ Not powering on

Well I thought it worked properly. After replacing the part the same problem exists. I have 5v from ground to input, but had a short from ground to output. Still work with jumper wire from other 3.3v regulator. Removed electrolytics in the area and short is still there.

[knoxrebel]

Re: Acer GD235HZ Not powering on

Any suggestions. Also found that if i get 5v from another spot on the board to the input of the ldo then it works properly. Only gettning .5v at input with new component installed. And without component installed I get 5v. Also measuring from ground to output with no component and I get low resistance.

[budm]

Re: Acer GD235HZ Not powering on

Any suggestions. Also found that if i get 5v from another spot on the board to the input of the ldo then it works properly. Only gettning .5v at input with new component installed. And without component installed I get 5v. Also measuring from ground to output with no component and I get low resistance.

That does not make sense that it works OK when you sourcing 5V from other spot, it is telling me that the original 5V source has high impedance.
The original 5V spot should show low resistance to the other 5V spot since they are connected to the same 5V source from the power supply board.

[knoxrebel]

Re: Acer GD235HZ Not powering on

So just to see if anything changed i took the second regulator and moved it to the location of bad regulator and now i am getting the correct output voltage.

The original regulator was a ame8815 becs330 and i was sent a 17-33 as a replacment.

Is this not a compatible part? If not then why.



Thanks for all the help so far BUDM

https://cdn.badcaps-static.com/pdfs/...240f3eaef5.pdf

[budm]

Re: Acer GD235HZ Not powering on

Well did you find out if the 5V source feeding the input of this regulator show less than one Ohm to the other 5V source that works?

' Also found that if i get 5v from another spot on the board to the input of the ldo then it works properly"