Re: LED 27" monitor PSU issue - np power to LED array
Good idea, I'll order one, they don't cost much.
They guy who gave it to me said it just went off one day and never came back on.
Dougie....
dougieT
Member
Last Activity: 08-21-2023, 09:10 AM
Joined: 08-02-2022
Location: Edinburgh
-
Re: LED 27" monitor PSU issue - np power to LED array
And big thank you to you too
The 5v-3.3v reg IC was definitely reading very low even though there was 5v getting to the motherboard from the PSU.
Maybe supplying the external 5v 'reset' the regulator IC?
Strange indeed.
Dougie....Leave a comment:
-
Re: LED 27" monitor PSU issue - np power to LED array
I've assembled it back in the casing, I'll leave it on for a while...
So, it's now powering up and displaying.
Dougie....Leave a comment:
-
Re: LED 27" monitor PSU issue - np power to LED array
Very strange!
I connected all the headers and the panel flat cable to test the 5v from the PSU header board again, the power led lit up and I cot a check cable message on the LCD panel
I'll put everything back in the casing and test with an HDMI input etc...
Dougie.Leave a comment:
-
Re: LED 27" monitor PSU issue - np power to LED array
Yes, I wouldn't expect these ICs to draw much, datasheet notes 3A typical and 5A max and I wouldn't expect it to need that much.
I applied 5v from the bench supply to pin 3/Vin on the 5-3.3v reg IC and got 3.3v pin2/Vout then tested at pin3/Vout on the 3.3-1.2v reg IC and it read 1.2v so all good there.
The power LED lit up and I was able to power on/off the motherboard via the on/off button. I only connected the front panel button/LED board header and nothing else.
...Leave a comment:
-
Re: LED 27" monitor PSU issue - np power to LED array
Thanks, good find!
Both regulator IC output readings are low, but the 1.5v reg IC Vin is fed from the 3.3v reg Vout so we can assume the 1.5v reg is OK? It relies on the 3.3v from the other reg IC and Vin has to be 1.5v higher than Vout, its Vin is currently only getting 1.52v.
Could a fault in the 1.5v reg IC take out the 3.3v reg IC?
So, maybe best to replace both...
Dougie....Leave a comment:
-
Re: LED 27" monitor PSU issue - np power to LED array
The 5v to 3.3v regulator on my board is a CYT8117T33 and the IC it feeds its output to pin 3 of this package labelled "8912k 245168", can't find any info on the codes.
I checked he caps around them and all ok.
So 1st I'll order the 5-3.3v regulator and replace it.
Dougie...Leave a comment:
-
Re: LED 27" monitor PSU issue - np power to LED array
I've attached the photo with the 2 readings.
Thanks for your help
Dougie....Leave a comment:
-
Re: LED 27" monitor PSU issue - np power to LED array
Here's some shots of the AV/logic board, top and bottom sides.
I don't see any obvious issues or where the fault could be on the board.
Dougie...Leave a comment:
-
Re: LED 27" monitor PSU issue - np power to LED array
No lights to indicate it's on after mains power applied, soft power switch doesn't light up.
I took some readings from the AV panel driver board, pic attached.
Dougie...Leave a comment:
-
Re: LED 27" monitor PSU issue - np power to LED array
Looks like a slight bulge on it, took it out and measured in the mini tester. I replaced it with 2 x 47uF 63v in series and got a good spec and ESR.
The replacement E19 caps read 39v across it.
Dougie....Leave a comment:
-
Re: LED 27" monitor PSU issue - np power to LED array
I checked 2 surface mount TO-262 packages in the 24v test point area of the board, part numbers 050N10 and S20N10, desoldered and checked them in the mini tester. Also tested the gate switch function OK with a DMM. See pic for results.
Dougie....Leave a comment:
-
Re: LED 27" monitor PSU issue - np power to LED array
So time for some readings...
Heres a pic of the underside, there are 2 test points labelled on the PCB, one for 5Vdc and one for 24Vdc.
I also read the mains AC (244Vac) and rectified DC at the 2 paralleled 53uF 450v filter caps (336Vdc).
Took some readings at the other caps too, see pic.
Dougie....Leave a comment:
-
LED 27" monitor PSU issue - np power to LED array
Hi all, picked up a faulty Hanns-g HL272HPB free for spares/repair hoping it was just a re-cap...
I found 1 cap with a bulge and an out of spec reading.
100uF 100V see pics.
I've replaced it with a like for like value.
Not so fast... still no power on
More testing results next post.
Dougie... -
Re: Hannspree HT231HPB - PSU Question
For unknown connector polarity I've traced from where the centre pin enters the PCB to where there is a polarised component, an electrolytic capacitor is a good one to find.
Dougie...Leave a comment:
-
Re: New Members - please post your introductions here
Hi all, let's fix those displays...
DougieLeave a comment:
No activity results to display
Leave a comment: