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jalinsta



Joined: 04 Dec 2013
Posts: 6

PostPosted: Wed Dec 04, 2013 7:30 pm    Post subject: LG 32LD400 sc r7 no picture no sound Reply with quote

Lightning struck tree next door and tv went out. Replaced F1 on main board, part no. 0171-2271-3274 E370VL. Still no pic and no sound. IC MT5387 gets very hot. Power Supply voltages are normal at CN 201.
How can i check the display to see if it is ok. I don't want to buy a new main board if the display is shot. What value should hi voltage be on the display?
I m a former tv tech and still have high voltage probe, Digital multimeter, Scope and soldering equipment.
Thanks for your help in advance.
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JTS1957



Joined: 21 Jan 2009
Posts: 2305
Location: Far, Far Away

PostPosted: Wed Dec 04, 2013 10:04 pm    Post subject: Reply with quote

http://elektrotanya.com/lg_32ld400_lc320wug-scr7_42ld400_lc420wug-scr7.pdf/download.html
jalinsta



Joined: 04 Dec 2013
Posts: 6

PostPosted: Sat Dec 07, 2013 4:28 pm    Post subject: Reply with quote

Thank you for the quick reply and service manual. it Certainly is different from the ones we used to use. Haven't figured out how to test the screen without the main board not working. Any help would be appreciated.
JTS1957



Joined: 21 Jan 2009
Posts: 2305
Location: Far, Far Away

PostPosted: Sat Dec 07, 2013 5:26 pm    Post subject: Reply with quote

TS chart Page 9-5? Are voltages all present?
jalinsta



Joined: 04 Dec 2013
Posts: 6

PostPosted: Mon Dec 09, 2013 7:17 pm    Post subject: Reply with quote

All voltages present except U10 pin 3 is 0.33 volts. this is a LM39102. Data sheet shows pin 2 as Vin and is 5 volts. Checked pin 3 again, 0.33 v.
U15, MT5387 is running hot at 136 degrees F. Does'nt get any hotter.
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JTS1957



Joined: 21 Jan 2009
Posts: 2305
Location: Far, Far Away

PostPosted: Mon Dec 09, 2013 8:02 pm    Post subject: Reply with quote

jalinsta wrote:
All voltages present except U10 pin 3 is 0.33 volts. this is a LM39102. Data sheet shows pin 2 as Vin and is 5 volts. Checked pin 3 again, 0.33 v.
U15, MT5387 is running hot at 136 degrees F. Does'nt get any hotter.


What is resistance pin 3 to ground? DVM 'ohms' function; NOT 'diode check.'
jalinsta



Joined: 04 Dec 2013
Posts: 6

PostPosted: Tue Dec 10, 2013 8:30 am    Post subject: Reply with quote

Pin 3, u10 is 4k to ground on 20k scale, no reading on the 200 ohm scale and 1k on the 2k (diode check) scale.
Many thanks for your help.
JTS1957



Joined: 21 Jan 2009
Posts: 2305
Location: Far, Far Away

PostPosted: Tue Dec 10, 2013 3:15 pm    Post subject: Reply with quote

What voltage is on the enable pin (Pin 1)?
Enable pin is active 'high.' IF it is high:

Do you have a external power supply to momentarily replace the 5 volts (up to 1 Amp) on U10 Pin 3?
jalinsta



Joined: 04 Dec 2013
Posts: 6

PostPosted: Tue Dec 10, 2013 9:28 pm    Post subject: Reply with quote

The voltage on pin 1 is 0.74 v.

I do have a 5 v supply.
JTS1957



Joined: 21 Jan 2009
Posts: 2305
Location: Far, Far Away

PostPosted: Tue Dec 10, 2013 9:58 pm    Post subject: Reply with quote

TS chart does seem to indicate that 5 volts should be present. It does NOT seem to say which input, if any or all, the chart applies to. The enable pin on U10 acts as a switch to turn IC output voltage on/off. It appears to supply the tuners.
You have No pix/No sound, and I presume you have no way of telling which input the unit has selected nor if pressing the 'input' key is having any effect.

You can monitor the output pin 3 (for 5VDC) while you apply your own enable voltage to pin 1.
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