Re: LG Power supply board has no standby voltage.
HI Budm, I have found a circuit schematic that is the same as the power board I have here.
Thanks for that info on how the IC works, I was looking at the circuit and tracing it back through components to try and figure out where the VCC voltage is generated. I will have another closer look at that startup circuit and see how that goes....
br777
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Last Activity: 01-18-2023, 09:45 PM
Joined: 09-24-2017
Location: Auckland
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Re: LG Power supply board has no standby voltage.
Hi, I got confused as to what IC you were referring to initially, as the one in the pdf you attached does not correspond to what I have on this board. The pdf I attached in post 15 is the datasheet for IC501. I have checked the resistance between VCC and GND of IC501 and it is 340 kOhmsLeave a comment:
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Re: LG Power supply board has no standby voltage.
I get 345kOhms
the datasheet i was referring to is this one. it is slightly different to the one in your link
Edit
Are you referring to IC101 in your previous post?
IC101 has 18 pins rather than 12 as in the one in your link...Last edited by br777; 11-06-2017, 04:34 PM.Leave a comment:
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Re: LG Power supply board has no standby voltage.
Still no luck in fixing this one so far....
I was getting some strange readings from my old DMM for the resistors so bought a new one, hence some of the readings are different to previous posts. I suspect one of the leads was no good on the old one and it affected the readings.
R510 ansd R511 both measure 0.8 ohms.
I have checked all of the diodes with no issues at all. They all have current flow one way, and none the other. The 3 on the secondary side that appeared to have current both...Leave a comment:
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Re: LG Power supply board has no standby voltage.
Thanks for your help. I will test those components and see what i find. Meanwhile, here is a photo of IC501, not sure which of the numbers is the actual part number....Leave a comment:
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Re: LG Power supply board has no standby voltage.
Yes, that has 122 v DC on both sides of it.Leave a comment:
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Re: LG Power supply board has no standby voltage.
Hi,
Yes the 364 v was from standby state. As far as I can see I can't test any other way as there is no standby voltage to the main board for a power on trigger.
I don't hear any relay click when I plug in the power cord. Does this relay activate transformers to reduce the voltage to the secondary side?
I tested the pins on what I think is a transformer (yellow on right hand side, bridging the primary to secondary to line) and it has around 110v (from memory) on the primary side, but nothing on the secondary...Last edited by br777; 11-03-2017, 04:40 AM.Leave a comment:
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Re: LG Power supply board has no standby voltage.
I have tested the diodes with the multi meter. D255 and 256 seemed to have current both ways, but when snipped on one side out of the circuit they were fine.Leave a comment:
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Re: LG Power supply board has no standby voltage.
Hi, thanks for your input.
I have re-soldered the fuse F100, and checked for continuity whilst in the circuit. It seems to be fine. With power on, there is no voltage either side of this fuse though, perhaps it will ramp up when the set gets switched on? (When i can somehow get voltage to the main board)
The cap C610 has 364v across it
Fuse F101 is testing ok, and has 122v either side of it.
I have seen other troubleshooting posts suggesting have s look at D501. With the black probe...Last edited by br777; 11-02-2017, 03:34 PM.Leave a comment:
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LG Power supply board has no standby voltage.
Hi guys,
I have an LG Power board EAX64905601 from a 55LA6230 LCD.
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From a fair bit of research I found that it was likely to be the LED array that was the issue. (LED + voltages fine, no LED - voltage)
I checked Connector P201 and all voltages were normal there, so I thought power supply was ok.
After I stripped the TV down (took power supply board off to lay it face up to get LCD panel off) and did some investigating on the LEDs I wanted to see if they would... -
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Re: Samsung LED TV troubleshooting. Help is very appreciated!
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