REPAIRING AND NOT THROWING AWAY

REPAIRING AND NOT THROWING AWAY

Richtige Fernseher haben Röhren!

Richtige Fernseher haben Röhren!

In Brief: On this site you will find pictures and technical information about Service Modes, Circuit Diagrams, Firmware Update procedure, Disassemble procedure, Universal remote control set-up codes, Troubleshooting and more....

If you go into the profession, you will obtain or have access to a variety of tech tips databases HERE IT IS Master Electronics Repair !.

These are an excellent investment where the saying: 'time-is-money' rules. However, to learn, you need to develop a general troubleshooting approach - a logical, methodical, method of narrowing down the problem. A tech tip database might suggest: 'Replace C536' for a particular symptom. This is good advice for a specific problem on one model. However, what you really want to understand is why C536 was the cause and how to pinpoint the culprit in general even if you don't have a service manual or schematic and your tech tip database doesn't have an entry for your sick TV or VCR.

While schematics are nice, you won't always have them or be able to justify the purchase for a one-of repair. Therefore, in many cases, some reverse engineering will be necessary. The time will be well spent since even if you don't see another instance of the same model in your entire lifetime, you will have learned something in the process that can be applied to other equipment problems.
As always, when you get stuck, checking out a tech-tips database may quickly identify your problem and solution.In that case, you can greatly simplify your troubleshooting or at least confirm a diagnosis before ordering parts.

Happy repairing!
Today, the West is headed for the abyss. For the ultimate fate of our disposable society is for that society itself to be disposed of. And this will happen sooner, rather than later.

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..............The bitterness of poor quality is remembered long after the sweetness of todays funny gadgets low price has faded from memory........ . . . . . .....
Don't forget the past, the end of the world is upon us! Pretty soon it will all turn to dust!

©2010, 2011, 2012, 2013, 2014 Frank Sharp - You do not have permission to copy photos and words from this blog, and any content may be never used it for auctions or commercial purposes, however feel free to post anything you see here with a courtesy link back, btw a link to the original post here , is mandatory.
All posts are presented here for informative, historical and educative purposes as applicable within fair use. NOTHING HERE IS FOR SALE !

Tuesday, 19 February 2019

LG 47LG90 POWER SUPPLY BOARD TESTING

LG 47LG90 POWER SUPPLY BOARD TESTING

SMPS check
  AC Should not be applied any time while adding resistors, or while unplugging connectors, as damage to the circuit PWB may occur.
  • The SMPS PWB "must" be producing Stby 5V, on pins 9,10,11 or 12.
  • Must be generating ACD [AC detect] pin-18 check for 5V.
If none or any one among the said condition are not met, the SMPS PWB is defective, and must be replaced.  There is no need to continue with any more test.
Unplug P800 on main PWB and P205,P205 to the inverters.
Add a 10K resistor between Pin-9,10,11 or 12 & Pin-19 (PWR). Apply AC.  This will turn on the power supply. 
  • Check that 16V and 12V power supplies are turned ON, P201[16V pins 1&2] [12V pins 5&6]
  • Check that the 24V [inverter B+] is turned ON on P 205 and P 204 pins 1-5.  
If OK, the power supply is working well.  Remove AC power, and re-insert plugs P204/P205 to the inverters.
If the above test is sucessfull. proceed:
Add a jumper wire between pin-20 (INV On/Off) to pin-19 (PWR)
Apply AC power.  This simulates a Power On and Back light On command.
Observe the back lights should turn On.  They will be dim.
If no back light activity. reconfirm 24V is being generated and output on P204/P205 connector pins 1-5.  If not, unplug P204 OR P205 and recheck.  If not, SMPS is defective.  If yes, inverter is loading down the 24V line.
If all the above are normal, check the voltage on inverters.
Posted By: FRANK at 05:59
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