Haier L37A9A-A1 NO POWER

[s_henya]

Hey guys,

Got this LCD today,

Symptoms: No power at all,

quick check on PSU:
"AD301M24-4N1" PCB

1. C52 Capacitor 150u 400V Open and bulged, replaced for 100u 400v i had just for a quick test.
2. F1 Fuse 250v 6A- Open, Replaced with same fuse.
3.Q8 Power mosfet IRFP640 shorted, need to find one, or order online.

Bridge rectifier checked OK, Second IRF OK

all the other elec' caps were check Ok.

No overheating signs, PCB looks in pretty good condition.

anything else you would recommend checking before powering on,

(dont want to burn the new Q8).

Thanks,

Shai.

[s_henya]

Re: Haier L37A9A-A1 NO POWER

front and back pics

[budm]

Re: Haier L37A9A-A1 NO POWER

When power MOSFET shorted out, the Gate drive components and the IC that drive the Gate can be damaged also, the resistor connected to the Source pin (if it has one) can be blown open also. It may also have blown fusible resistor for feeding the B+ to the Drain circuits.

[s_henya]

Re: Haier L37A9A-A1 NO POWER

first try no luck :-(

fried the fuse Q8 and R29 R41

anyone got a schematic? need the values of the resistor

(they are the same)

your advice is more than welcome

[budm]

Re: Haier L37A9A-A1 NO POWER

The IC that drives the MOSFET is also bad, the output is stuck high in stead of switching it on and off.
P/N of the IC? Good closed up pictures of the damaged components?

[s_henya]

Re: Haier L37A9A-A1 NO POWER

thank you budm, ill upload pictures of the ic, when i get home
the bang happened, not at feeding AC, but after pressing the power botton
Do you know this PCB?

[s_henya]

Re: Haier L37A9A-A1 NO POWER

A little update,

Found and replaced two bad caps(high ESR): 1000u 16v
100u 25v

and found this post while looking for clues,
unfortunatlly he gave up :-(
https://www.badcaps.net/forum/showth...t=AD301M24-4N1

identical pcb, simillar symptoms,

i need to replace 2 resistors, 1 fuse, 1 mosfet, and by budm the ic.
the cost of the parts is really cheap no more than 10 bucks
and of course i prefer fixing the PSU myself (learning expirience).
it will be the first time i will replace an IC.

my dillema is:
buy some more parts, a couple of bucks (waiting 2 weeks)
or buy the whole board for 60 dollars (waiting the same time)

Because i have no expirience in this sort of repair (Ic replacing)
what are the odds of fixing?

[JonathanAnon]

Re: Haier L37A9A-A1 NO POWER

The repair kit may help you reduce the odds on working out what's failed..

http://www.ohmsupplies.co.uk/KiT14-R...ER-XT37-AD301M

AD301M24-4N1 REPAIR KIT
USED IN THE FOLLOWING MODEL:
Bauer XT37
Whats in the kit?
F1
U3
Q8
Q3
R1
R77
R39
R75
R42
R29
R41
R36
NOTE: WE ADVISE CHANGING C52 100uF 400V MAINS SMOOTHING CAPACITOR ALONG WITH THE KIT AS IT CAN CAUSE FUTURE PROBLEMS AND MAY EVEN BLOW AGAIN.

I would focus on checking these components first..

[s_henya]

Re: Haier L37A9A-A1 NO POWER

Thanks for the effort jonathan, i saw this kit while searching for clues,
I'll try and check the resistors,
I have no clue how to check the IC
Q3 is fine,
Will have to replace Q8 and F1 again :-(
(need someone to explain me the light bulb tick...:-))

by the way is this resistor calc any good?
dont know which resistors to buy,(ohm,watt)

[JonathanAnon]

Re: Haier L37A9A-A1 NO POWER

Yeah that resistor calculation looks good.. Its a current sense resistor.. It's probably beside the PWM IC which works out the current by checking the voltage drop across this resistor, and if it's too large it shuts down.. Fairly common for them to blow.. Not sure of the wattage..

It's very hard to test the ICs but I've found with a couple of those PWM ICs that they short from Vcc to one of the other pins... (you can find the pinouts by googling for the datasheet for the IC)... You wont be able to prove that it's working but you may be able to prove that it's shorted..

The light bulb trick is putting a light bulb in series with the live side of the power input.. There are a number of ways of doing this but some people simply solder a lightbulb in place of the main fuse.. The bulb will turn bright and stay bright if there is a short on the board... It will flash bright initially before dimming if there is no short on the board.. either way it protects the components on the board from blowing again if there is a short...

I'm sure there must be a guide on here somewhere. But be sure you know fully what you are doing before attempting it, cos you're dealing with high voltages..

[s_henya]

Re: Haier L37A9A-A1 NO POWER

Here are the testing results of the parts in the kit:

F1- 250V 6A->BAD
U3- L6562D Don't know how to check it
Q8- IRFP460 BAD
Q3-IRFP460 BAD
R1- SMD 152->1.5Kohm GOOD
R77- SMD 4R7->4.7ohm GOOD
R39- SMD 4R7->4.7ohm GOOD
R75- SMD 220->22ohm GOOD
R42- SMD 220->22ohm GOOD
R29-red->white->silver->gold->yellow 0.29ohm BAD
R41-red->white->silver->gold->yellow 0.29ohm BAD
R36- SMD 102->1Kohm GOOD
C52-> 150u 400V BAD replaced with 100u 400V

C67->1000u 16V BAD replaced
C??->100u 25V BAD replaced
Q8 had me fooled last time i check it, its not totally shorted

any tips about the ic?

[tom66]

Re: Haier L37A9A-A1 NO POWER

The resistors measuring 0.29 ohm are probably good if they are 0.39 ohm rated; the measurement is so small your meter can easily make an error.

[JonathanAnon]

Re: Haier L37A9A-A1 NO POWER

That's a lot of bad components though... And you may have damaged more components not on that list when it blew the second time.. :-(

Still, find the numbers on the IC.. Then we'll see if we can locate the datasheet...

[s_henya]

Re: Haier L37A9A-A1 NO POWER

couldnt find the u3 l6562d
got the 2 mosfets
2 resistors couldnt find the exact value
so i got 0.33 ohm instead
couldnt find the fuse, took 7a pico fuse instead
ill try the lamp trick, and hope for the best
any last advices?

[budm]

Re: Haier L37A9A-A1 NO POWER

I will not do anything until you get the new IC.

[JonathanAnon]

Re: Haier L37A9A-A1 NO POWER

That's PFC controller..

http://www.alldatasheet.net/datashee...CS/L6562D.html

My supplier, Radionics, has that chip... but they are UK/Ireland..

http://radionics.rs-online.com/web/c...D&x=-447&y=-21

[budm]

Re: Haier L37A9A-A1 NO POWER

You should download the data sheet of the IC so you can see how it is used and connected, it will be real close to what you have in your board.

[s_henya]

Re: Haier L37A9A-A1 NO POWER

I decided not to be tempted and run it without replacing the IC.
I invested too much time and money on this TV, to burn all the parts again,
(and its not my lucky day today anyway :-( so the odds where against me)
I ordered online (thank you god for Ebay), 2 pcs from china for 3.79 dollars.

budm i looked at the datasheet, im just starting to learn the real stuff of electronics at college, but i still dont have a clue about most of the stuff there :-))

is there any info that i could use to check whether its good or bad?

buy the way how am i supposed to get it out anyway?
getting parts out of this PCB is really hard,
(the soldier wont wick out, only after a few tries with fresh soldier)
i have ATTEN 8586 rework station, with HOT air.
(which temp should i use)

[JonathanAnon]

Re: Haier L37A9A-A1 NO POWER

Just to clarify, you have ordered that l6562d chip already from China, yeah?If you want to check the old IC, I would first check that the Vcc pin is not shorted to one of the other pins... But if you have already ordered the new chip, I probably wouldnt bother..



You are better off using a soldering iron and a solder sucker (seen above) than that solder wick. I find that solder wick very frustrating to use, and time consuming.. Just heat the solder and zap it with the solder sucker and you will get a clean result..

With regard to the bulb tester we were talking about earlier, I posted my variation of the bulb tester on this thread.. (Be conscious that I am in Ireland so the colour of the wires may be different). https://www.badcaps.net/forum/showth...855#post332855 Be interested in your opinion on it too, Bud.

[tom66]

Re: Haier L37A9A-A1 NO POWER

Use wick on the surface mount stuff. Don't use wick on most through hole, it works but is slow.