Dynex dx-40l261a12 wont power on.

[itronic]

This model Dynex DX-40L261A12 tv will not power on. The standby light comes on and the PSU makes a clicking noise when power cord is plugged in. But thats all.

Connection point with power cord plugged in on PSU.

I'm thinking PSU but like other inputs. Thanks in advance.

Xp805:

gnd
gnd
stb
5v---4.8v
5v---4.8v
12v
12v
gnd
bri
sw
gnd
gnd
5v_m
5v_m

If i unplug XP1 on mainboard and jump 5v to stb is will click and you will hear the speakers come on then fade out.

XP805 connection points voltage when jumped:

gnd
gnd
stb----4.8 v when jumped
5v---4.8v
5v---4.8 v
12v----goes up to 4v then fades
12v----goes up to 4v then fades
gnd
bri
sw
gnd
gnd
5v_m-----3v then fades
5v_m-----3v then fades

[will62]

Re: Dynex dx-40l261a12 wont power on.

Here's a video of NorCal715 repairing a 153024 power supply that wasn't getting the 12v.

https://www.youtube.com/watch?v=L8nj3CpiEKY

[itronic]

Re: Dynex dx-40l261a12 wont power on.

Thanks Will62. I'll check it out.

[itronic]

Re: Dynex dx-40l261a12 wont power on.

okay checked out video but his board had a different issue. I know the power board is the problem. Best way to troubleshoot the PFC circuit. This is what i know so far.

Xp805:- have stby jump with 1k.

gnd
gnd
stb---4.8v
5v---4.8v
5v---4.8v
12v
12v
gnd
bri
sw
gnd
gnd
5v_m
5v_m

Other readings:
C810----219---this is a 250v390uf
c903----167v
c814----9.17v to 12.32v
vz812---9.33 to 11.67v

N831
pin 12--- 7.47v to 8.14v

n811
pin 8---9.42 to 11.66v

will send more readings once i get them.

[R_J]

Re: Dynex dx-40l261a12 wont power on.

When you jump +5v to stby, what is the voltage on C810? Try replacing C811, C812 (10µf/25v) & C814 (22µf/50v)

[itronic]

Re: Dynex dx-40l261a12 wont power on.

c810 is 219v .

[R_J]

Re: Dynex dx-40l261a12 wont power on.

The pfc voltage on C810 should be around 300~380v. If it was not working at all the voltage would likely be 160v, so the pfc circuit is trying to work, so try replacing the caps I suggested

[itronic]

Re: Dynex dx-40l261a12 wont power on.

Understand, but were the C810 is rated for 390uf/250v it will not go above 250v will it? just trying to understand it.

[R_J]

Re: Dynex dx-40l261a12 wont power on.

I guess the pfc circuit must only charge the cap to 220vdc. so the pfc circuit must be working. the normal voltage from a bridge rectifier (120vac input) is about 160vdc.
It's that pfc circuit that also supplies the VCC for N831. If C812 & C811 are bad (open) they will not charge up to develope the vcc.

[will62]

Re: Dynex dx-40l261a12 wont power on.

Take a look at the attached schematic. I believe this is for your board.

[nomoresonys]

Re: Dynex dx-40l261a12 wont power on.

.

[itronic]

Re: Dynex dx-40l261a12 wont power on.

Thank you for your help. I check the C811 and C812 and C814. Using a digital meter in Cap mode. All three read a little low in the circuit. Took them out and read them and they read a little low. I used a Cap instrument that shows me % loss and check each one again. This time the C814 was showing 9.6 % loss and the C811 and C812 was showing like a 6% loss. So after replacing these Caps. I picked up my 12v. Will post new connections readings tomorrow. Also tv is working now.

[nomoresonys]

Re: Dynex dx-40l261a12 wont power on.

Glad to hear it, another case of the caps looking good but being bad.

[itronic]

Re: Dynex dx-40l261a12 wont power on.

Okay, here is readings with everything hooked up and tv turn on.
Thanks again for everyone help.

Xp805:

gnd
gnd
stb---2.4
5v---4.8v
5v---4.8v
12v--11.72v
12v--11.72v
gnd
bri---2.6v
sw--4.8v
gnd
gnd
5v_m--5.16v
5v_m--5.16v