Re: Sharp LC-50UB30U. Completely dead, no power indicator.
Hello, folks.
Had to sidetrack the project a bit. Anyway...
Replaced all of the OE LED strips with those from a Vizio. Will post pix if there is interest. What I did not take into the account was the lower working current of the Vizio LEDs.
CURRENT (ma) as MEASURED for 1 LED @ 3.3v
SHARP 460
VIZIO 240
The LEDs light up and shut down just as it has been described[URL="https://www.badcaps.net/forum/showthread.php?t=60208"] in post #3 of this...
HAHOMETP
Senior Member
Last Activity: 12-11-2020, 08:20 PM
Joined: 11-28-2012
Location: Philadelphia, PA
-
Re: Sharp LC-50UB30U. Completely dead, no power indicator.
You are right, neilc6. A quick search on Sharp LC-50UB30U reveals four threads (this one included), all of which site burnt LEDs as the cause of malfunction. Apparently Sharp used some garbage LEDs in this particular model/family.
Still, just for giggles with a heat gun and solder paste in hand I replaced two individual LEDs (circled in GRN) on one strip, combined 4 good strips into one good channel and powered it up. The channel lit up and within a couple of minutes yet another LED went dim (circled in RED)....Last edited by HAHOMETP; 09-16-2020, 06:57 PM.Leave a comment:
-
Re: Sharp LC-50UB30U. Completely dead, no power indicator.
Right on the money, R_J!
I have a few LED strips pulled over time from various TVs with broken screens (mostly VIZIOs) - should be able to find replacement LED chips. I don't think some variance in the colour temperature if any will be visible through the diffusers.
Attached are the two pairs of pix: (the LED channel + its driving voltage as indicated by the LED tester) x 2....Last edited by HAHOMETP; 09-10-2020, 05:57 PM.Leave a comment:
-
Re: Sharp LC-50UB30U. Completely dead, no power indicator.
Before taking the TV completely apart decided to connect the MB to the PSU and run the same tests again.
CN102, 103 and 105 are connected at the PSU.
J1 (System Power) and J2 (Power In) are connected at the MB for the first time for these tests.
REMOTE_ON, BACKLIGHT_ON, DIMMER1 and DIMMER2 are all pulled up to +5v via 1k resistors.
C120a and C120b:
STANDBY: +158v, steady.
REMOTE ON: +384v, steady.
CN102-PIN9, 10: +12v, steady.
CN103-PIN1,...Last edited by HAHOMETP; 08-29-2020, 08:49 AM.Leave a comment:
-
Re: Sharp LC-50UB30U. Completely dead, no power indicator.
Connected the 230v DC LED tester across the top LED strip at CN105. The strip lit up (visible through a hole in the chassis), the driving voltage settled @ +77.6v.
Connected the 230v DC LED tester across the bottom LED strip at CN105. The strip lit up (visible through a hole in the chassis), the driving voltage settled @ +77.7v.
It appears that the numbers of lit up individual LEDs in both strips are the same, else I would expect some difference in voltages roughly in the increments between 2.5v and...Leave a comment:
-
Re: Sharp LC-50UB30U. Completely dead, no power indicator.
Thanks for the advice, R_J, will check the LEDs. I have a dedicated digital LED tester (a self adjusting current source), will try lighting the LED strips individually. Should be easy since there are only two sets of two wires at CN105. If one pair of wires shows less driving voltage than the other pair it would indicate a burnt LED in that particular strip.Leave a comment:
-
Re: Sharp LC-50UB30U. Completely dead, no power indicator.
Received a replacement board today. The seller has 17k+ feedbacks, 99.3% positive. The pic shows a powered up TV with a lit up broken screen and the power indicator on. I have no reason to suspect dishonesty.
I installed the board onto the chassis and connected _only_ the mains power cord.
C120a and C120b:
STANDBY: +162v
REMOTE ON: jumps to +364v, then drops down to +223v in 16 seconds, then jumps to +375v and so on.
The +12v pin acted the same way also (+10v => +7v =>...Last edited by HAHOMETP; 08-27-2020, 06:51 PM.Leave a comment:
-
Re: Sharp LC-50UB30U. Completely dead, no power indicator.
Just tested. Conditions:
CN102-PIN12,13,14 @ zero.
CN102, CN103, CN105 disconnected.
C603 in standby: +14.7v
C603 when CN102-PIN11 pulled up to +5v: +11.7v...Leave a comment:
-
Re: Sharp LC-50UB30U. Completely dead, no power indicator.
C603 in standby: +14.88v, steady....Leave a comment:
-
Re: Sharp LC-50UB30U. Completely dead, no power indicator.
Yep, 1:1....Leave a comment:
-
Re: Sharp LC-50UB30U. Completely dead, no power indicator.
At first I thought that the D121A, D121B, D120A & D120B were arranged in a bridge, but then again, why not use a dedicated bridge instead? After a closer look I see that the D121A and D121B are in series, whereas the D120A and D120B are parallel. Bizarre. Anyway, no shorts, and no open circuits, although in theory either the D120A or the D120B could be open and not show it in situ masked by the other diode. I seldom see blown power diodes except perhaps in automotive alternators. If need be I can desolder...Leave a comment:
-
Re: Sharp LC-50UB30U. Completely dead, no power indicator.
ZD604 if viewed sideways (pins East-West) under the microscope: ||||| DZ then W47 turned 90° CCW.
Tested good in situ.
C603: 22uF x 50v, 105°C, Nippon Chemi-Con, 21.2uF as measured.
Replaced with a higher capacitance just in case, 33uF x 50v, 85°C, Matsushita, 31uF as measured.
No difference....Last edited by HAHOMETP; 08-23-2020, 06:51 PM.Leave a comment:
-
Re: Sharp LC-50UB30U. Completely dead, no power indicator.
Yes, CN103 was disconnected.
PFC voltage was taken with the old analogue multimeter with the range set to 1,000v DC. If taken with the digital multimeter with MAX HOLD activated the PFC voltage first jumped to +390v; in subsequent cycles it showed +340v, +380v, +374v, +347v.
IC120: 1608B, like you said is a PFC Controller.
C603 voltage across its terminals is fluctuating between +11.62v and +11.74v, so yes, it is steady.
Q601 collector, base and emitter voltages...Last edited by HAHOMETP; 08-23-2020, 03:59 PM.Leave a comment:
-
Re: Sharp LC-50UB30U. Completely dead, no power indicator.
IC150: SSC9522S
C120a and C120b:
STANDBY: +164v
REMOTE ON: jumps to +340v, then drops down to +220v in about 13 seconds, then jumps to +340v and so on.
C155: 10uF x 50v, 105°C, Rubycon, 9.3uF actual as measured out of the board.
Replaced anyway just in case with a 10uF x 50v, 125°C, GXE, 11.1uF actual as measured out of the board.
No difference....Leave a comment:
-
Re: Sharp LC-50UB30U. Completely dead, no power indicator.
Thank you, budm!Leave a comment:
-
Re: Sharp LC-50UB30U. Completely dead, no power indicator.
With the backlight disconnected the +12v pins still jump to +9.8v and slowly drop to +6.4v in about 15 seconds. Attached are the pictures of both sides of the board, top and bottom.
I am beginning to suspect a cracked transformer Ferrite core....Last edited by HAHOMETP; 08-20-2020, 07:27 PM.Leave a comment:
-
Re: Sharp LC-50UB30U. Completely dead, no power indicator.
With all four ON/OFF CN102 pins pulled up to +5v the +12v pins jump to +9.8v, slowly fall to +6.4v and then jump to +9.8v again. These were taken with an analogue voltmeter.
Will do so in a lightbox with an SLR camera when get back home from work later today....Leave a comment:
-
Re: Sharp LC-50UB30U. Completely dead, no power indicator.
Quickly tested near every semiconductor in situ (except a few SMD chips on the track side) - no shorts, all show the expected voltage drop in the forward direction.
Could it be that the backlight strips have a few burnt LEDs that trigger the shutdown like the old fluorescent tube monitors did when one tube was out?
OTOH the standby LED on the front never comes on when the TV is plugged in. So if the +12v part of the PSU is out then the MB never gets powered up thus the MB never tells the standby...Last edited by HAHOMETP; 08-19-2020, 08:08 PM.Leave a comment:
-
Re: Sharp LC-50UB30U. Completely dead, no power indicator.
Yes, the 5VSTB is rock solid to the 3rd place after the decimal.
So it's not the MB... Will be pulling the PSU off the chassis tomorrow and checking every p-n junction on the board....Leave a comment:
-
Re: Sharp LC-50UB30U. Completely dead, no power indicator.
Thank you for the reply.
Both cables from PSU to MB removed.
If REMOTE ON/OFF pulled up to 5v via a 1k resistor:
CN102 +12v jumps to +11v and slowly falls down, 5 seconds later the process repeats.
CN103 +12v jumps to +11v and slowly falls down, 5 seconds later the process repeats.
CN105 LED1 jumps to +2.7v and slowly falls down, 5 seconds later the process repeats.
CN105 Vout1 jumps to +57v and slowly falls down, 5 seconds later the process repeats....Last edited by HAHOMETP; 08-19-2020, 04:29 PM.Leave a comment:
No activity results to display
Leave a comment: