Emerson LC401EM2F

[lilmonk3]

Re: Emerson LC401EM2F

Thank you for the help Budm

[budm]

Re: Emerson LC401EM2F

It is blowing the main fuse the minute you plug it into the outlet?
Please check the resistance reading (meter set to Ohm mode 200 Ohm range) for me as noted (board not installed or plug in).

[lilmonk3]

Re: Emerson LC401EM2F

I have an auto ranging DMM.. I have ohm and diode setting... No 200 ohm.. Which one would you like me to use.. I did just do some quick checking with it in diode mode and D1604,D1606 read 000 both ways, D1607 reads .488 and .493

[lilmonk3]

Re: Emerson LC401EM2F

And yes it blows the the fuse as soon as its plugged in if all boards are connected.. But if I unplugg the flat white ribbon cable that goes from the PS to Mainboard the fuse does not blow

[budm]

Re: Emerson LC401EM2F

OK, please check the resistance of the Diodes I red-lined in picture 1 & 2 tell me what you get.

[tom66]

Re: Emerson LC401EM2F

I am unsure on whether this is based on a self-resonant topology or not. It looks like it might use a controller IC. However, I was playing around with a real cheap wall wart today which used a self resonant circuit. When I shorted the output, it blew the mains fuse! So some of these self-resonant designs don't cope well with shorted loads.

[budm]

Re: Emerson LC401EM2F

Set meter to Ohm mode, auto range is fine, we are looking for shorted parts which will no longer act like semiconductor any more, it will read low Ohm in both directions.
Again, take the reading of the bad part off the board when it shows bad on the board to verify, you can just lift one leg off the board and take the reading also.
This power supply uses dual PFC circuits. The two MOSFET's may be shorted out, the B+ to the PFC is supply through the relay, so if the main is not connected, the PFC will not get any power to it, which is why it did not blow the fuse when main board is connected, the 5VSTBY SMPS is before the relay so it is always running with its own rectifiers which is OK since it did not blow the fuse.
I cannot see the number too well in the pictures.
Where are the D1604,D1606? Are they in the second pictures? the group of 4 in the bottom left of pic#2? My eyes are not that good.
This is what I come up with. The MOSFET or DIODE for the PFC may be shorted, or MOSFET for the SMPS may be shorted also.

[lilmonk3]

Re: Emerson LC401EM2F

Ok here are the readings of the diodes in pic 1 and 2 with one leg lifted..
D1201 OL 4.60
D1202 OL 4.90
D1203 OL 4.39
D1204 OL 4.21
D1604 00.3 00.2
D1606 OL 2.94
D1607 OL 4.84
D1608 OL 4.73
D1609 OL 5.26
D1610 OL 5.05

I marked up the board in the pics below .. My eyes are not very good either

[retiredcaps]

Re: Emerson LC401EM2F

Ok here are the readings of the diodes in pic 1 and 2 with one leg lifted..
D1604 00.3 00.2

D1604 is bad if that is tested out of circuit.

[lilmonk3]

Re: Emerson LC401EM2F

Thanks retiredcaps. Its sf38 .. Looks like I will have to order online.. Was hoping Ratshack would have something I could use just to get by.. Oh well

[lilmonk3]

Re: Emerson LC401EM2F

Do I have to stay with the exact spec of this diode.. I would LOVE to be able to run to ratshack to get a part that will work.. I am wanting to try to see if I can get this thing going by monday. My nephew is home from college for the holiday weekend and I wanted to give this TV to himm.. Any chance that ratshack would have something that would work??
Its a SF38,DIODE, ULTRA-FAST, 3A, 600V

[lilmonk3]

Re: Emerson LC401EM2F

http://www.radioshack.com/product/in...ductId=2062579

Would that work and be safe to use???

[selldoor]

Re: Emerson LC401EM2F

Not read if it is ultra fast but it is only 400v not 600 spec sheet attached
maybe ok for testing but I dont really know.
Perhaps other will know for sure.



Edit
Not even fast let alone ultra so if its in the PFC circuit I guess its no good.

[budm]

Re: Emerson LC401EM2F

Please check Q1602 as shown in my drawing also, just to be sure it is not damaged.
just label the pin as 1, 2, 3. Then using Ohm mode and report the readings:

1 & 2 =
1 & 3 =
2 & 3 =

The Diode should have at least the same Voltage and current rating.
The Vf must be equal or less.
The Trr must be equal or less

[selldoor]

Re: Emerson LC401EM2F

Re SF38,DIODE, ULTRA-FAST, 3A, 600V
Have you no other boards knocking about you could borrow one off?

Is this the nephew with the westinghouse - what happened to that?

[lilmonk3]

Re: Emerson LC401EM2F

Re SF38,DIODE, ULTRA-FAST, 3A, 600V
Have you no other boards knocking about you could borrow one off?

Is this the nephew with the westinghouse - what happened to that?

Sell.. Yes its the same nephew.. The westinghouse is still here laying on the bench.. With school starting , I have not been able to sit down and mess with it.. Its sitting there for a raining day I started to mess with it the other day, but got frustrated because of all the pulled pads, and I am not smart enough to figure out how to fix em .. I am going to dig around on some old boards today and see what I can come up with..

[lilmonk3]

Re: Emerson LC401EM2F

Do I have to say with the the 600V or can I go a little lower if I find one on a board that isnt the exact same specs.?

[tom66]

Re: Emerson LC401EM2F

In its location, you may be able to use 400V.

[lilmonk3]

Re: Emerson LC401EM2F

I found an old board and it has some IN5406 BL on it.. No sure what the BL means , but the datasheet on IN5406 is 3a 600v... So I will give it a try.

[tom66]

Re: Emerson LC401EM2F

I found an old board and it has some IN5406 BL on it.. No sure what the BL means , but the datasheet on IN5406 is 3a 600v... So I will give it a try.

In that position (if it is rectifying 50/60Hz AC), that diode is perfectly fine.