Funai lf501em4f chirping psu. no power on

[tucocaps]

I've been doing some research on this, and it seems it may be a shorted diode. Not sure on how to check all that right now, but I have a decent VOM now (bk precision).

I've attached pictures of the PS, and I believe that's where the chirp noise is coming from.

I've noticed others have posted similar problems with these funai/emerson sets. Thanks much for any help!

[tucocaps]

Re: Funai lf501em4f chirping psu. no power on

Been trying to test all the diodes. It seems that several may be bad, but I'm not sure if it's possible to test them all in circuit. The one diode that's clearly marked on the board is showing a .4 drop in both directions, which I've read indicates a short. However, another cluster of diodes above it real over 1 in one direction and .2 in another.

[tucocaps]

Re: Funai lf501em4f chirping psu. no power on

Well , after further review, it seems all the diodes do read OL in one direction, and .2 to .5 in the other. Except one very small one under a resistor (hard to get to). It appears to be a dead short (in circuit).

If I unplug the ribbon from the PS to the main, the noise stops. I really can't be sure the chirp is coming from the PS or the mainboard. It's hard for my ears to discern the location.

[tucocaps]

Re: Funai lf501em4f chirping psu. no power on

Well, I took that one diode out of circuit, and when I tested it , it wasn't shorting anymore

Not sure where to turn on this. Was able to isolate the noise to the power board, and to one half of the board. Guess I just need to know what else to test. Thanks for any ideas!

[stj]

Re: Funai lf501em4f chirping psu. no power on

chirping is caused by a short on the output.

so see what else is linked to the pads you lifted the diode from.
infact, see if unplugging the main board from the psu makes the short go away.

[budm]

Re: Funai lf501em4f chirping psu. no power on

Can we see the closed up pictures of this diode? D??
Any good straight shot pictures of both sides of the board?

[tucocaps]

Re: Funai lf501em4f chirping psu. no power on

I'm pretty sure unplugging the mainboard did make the chirp go away.

bud,

are you saying a picture of the diode I took out of circuit and tested? a picture of that, or the location for which it was removed? I haven't put it back in yet. Would like to try, but unfortunately, I have a crappy soldering gun, and my solder sucker tool has been lost, so all I have now is the crummy gun and some desoldering braid.

[budm]

Re: Funai lf501em4f chirping psu. no power on

The picture of the board where the diode is, both sides of the board.
This problem sounds familiar to a couple of threads at BC.

[fredaelsadany]

Re: Funai lf501em4f chirping psu. no power on

hallo
noise may come from any place in the tv . you are now sure that it is coming from ps board .
from where in the ps ? please take a wood stick (20cm) put it on one of the two output transformer then to the other . you wil hear clearly the noise from where it comes .
any way it happened with me and i found that the ELKO capasitor is dry and ps is still working but with noise and by the stick i know its source (sound go better in solds).
thanks

[CapLeaker]

Re: Funai lf501em4f chirping psu. no power on

That diode that shows shorted in circuit, may be parallel to a large wattage, low ohms resistor to GND. The chirping comes from a shorted output. Those Emerson's are so cheap a$$ made, that even cheap a$$ is too expensive.

Plug in the PSU without the main board attached and then with the main board. You have to figure out which voltage rail is shorting out.

[nojgib]

Re: Funai lf501em4f chirping psu. no power on

I'm dealing with one of these now with the same problem. I have marked where the noise is coming from on my unit in his photo. I haven't had the opportunity to check too much of it out yet. Seems what is marked AMP+13v only receives 6.5v and the P-on+21v only receives 11.3v on this supply. This is with nothing else connected to the power supply. I can take better photos tomorrow if needed.

[CapLeaker]

Re: Funai lf501em4f chirping psu. no power on

sounds like a bad cap, a feedback problem of the 21V/12V rail or the PFC. Search badcaps for "emerson" there are tons of threads.