Hisense 46K360MN

[Goznu]

I am trying to diagnose an issue with a tv for a friend and I was told it just shut off. I plugged it in and no audio, but I could shine my light inside and could see images. Sounds like backlight issues, smoke just emanated from the top of the set. I've got no problems working on this on a component level, but I currently am having issues removing the back panel. I have taken all the screws out all the way around the back and the 4 stand screws and the 4 mount screws. It feels like I'm going to break either the bezel or the back panel or worse, the screen itself. Is there a trick to removing the back panel or do I just need to pull a little harder? There are areas on the panel that seem like it wants to pull away from the rest of the tv, but I just don't want to break anything trying to fix this.

[Goznu]

Re: Hisense 46K360MN

I finally got it. I believe the manufacturer didn't think the screws alone would hold it so they decided to make the panel snap together with the bezel. Almost had to break it to slowly pry up all the way around. Seems kinda stupid.

[Goznu]

Re: Hisense 46K360MN

I saw smoke coming out of the tv and was able to take the panel off. I see one of the diodes on the power supply board was actually fried. I looked at the schematics and it looks like the one that's fried is a 1N5408 and the one next to it is a MUR460. I have a couple extra MUR460 from previous fixes. I don't know the specs on either diodes, does anyone know if the MUR460 would be a better replacement for the fried 1N5408? If I need to order the exact diode, I will do it, but if I had a replacement that would be as good or better, then I'd like to do that.

[budm]

Re: Hisense 46K360MN

1N5408, MUR460
How about showing the pictures of the board to see how the diode is being used?

[Goznu]

Re: Hisense 46K360MN

Here is the pic of the fried diode.

[budm]

Re: Hisense 46K360MN

Are the two diode connected in parallel? If they then what happen when you use two diodes that the Vf are not perfect matched then one will have more current flow than the other and then you get thermal runaway on that diode and it will burn up.
Is this your board?
http://www.shopjimmy.com/hisense-164...upply-unit.htm
If it is the same board then:
UD808 is not the same as UD807. UD808 (MUR, ULTRAFAST RECTIFIERS, 600V 4A) is for boosting the Voltage (about 400VDC) generated by the PFC circuit, UD807 (1N5408, General purpose 1000V 3A) is also part of the PFC but different function.
You should just get the same as original or go with higher current rating but still 1000V rating.

[Goznu]

Re: Hisense 46K360MN

That looks like the board I have.

[Goznu]

Re: Hisense 46K360MN

I haven't checked anything else on the board. The indications at the beginning were that the tv just shut off and wouldn't turn back on. I turned it on and could see a picture with my flashlight. After being on for a short time, i did see a little smoke coming out of the top of the tv. Then I found this.

[Goznu]

Re: Hisense 46K360MN

Hll-4046wk.

[budm]

Re: Hisense 46K360MN

I updated post 6, you will need to check the component connected to the CATHODE side of the diode with ref to the primary circuit GND (Negative leg of the main filter cap) to see if any of them show <100 Ohms reading or so.

[Goznu]

Re: Hisense 46K360MN

The cathode sides of 807 and 808 tie in together and into a jumper and to the positive leg of C829 (82uf/450v), which I believe would be the main filter cap. I read continuity at .2 ohms to the positive leg and from there, nothing to ground. The negative leg of the cap reads nothing to ground also, which, by looking at the schematics, it should.

[Goznu]

Re: Hisense 46K360MN

Looks like I need to use exact diodes. It appears that both 807 and 808 are bad.

[budm]

Re: Hisense 46K360MN

The cathode sides of 807 and 808 tie in together and into a jumper and to the positive leg of C829 (82uf/450v), which I believe would be the main filter cap. I read continuity at .2 ohms to the positive leg and from there, nothing to ground. The negative leg of the cap reads nothing to ground also, which, by looking at the schematics, it should.

You are working in the primary side of the circuit, the Gnd ref of the primary circuit is NOT connected to the chassis GND, the negative leg of the main filter cap IS the GND ref. for the primary circuit.
Those two diodes are part of the PFC Voltage booster circuit that is why the Cathode of the two Diodes are tied together and connected to the + leg of the main filter cap, so you need to check the resistance between the - and the + leg of the main filter cap to see what you get, then remove the other diode (UD808) and test it off the board, then also check the resistance between the empty pads of each diode to see what you get.

[Goznu]

Re: Hisense 46K360MN

I get about 48 Megohms across the main filter cap and it tests at about 76.7 Microfarad. And 808 was actually good, quite surprised. I have about 2 Megohms across each pad to the jumper. I am concerned about C845, it was scorched when the diode blew and the values on the schematics aren't real clear. It states 103/630v and my reading off the board is 7 Nanofarads. From the research I did, the writing on the capacitor is a lightning bolt inside a circle for the manufacturer and next to it MMKP82 and under that 682J1KV. 682 seems like .068 Microfarad and the J would be 5% tolerance and the 1KV for 1000 volt rating. I can't seem to find this anywhere and I'm not really even sure that is the correct rating for this. I would just replace it, if I could find a suitable replacement or find out the exact value that it's supposed to be. I've included a pic of the capacitor.

[budm]

Re: Hisense 46K360MN

That will be 0.0068uF 5% 1000V
MKP is Polypropylene Capacitors type.
So your capacitance reading of 7nF is OK.

https://cdn.badcaps-static.com/pdfs/...40ddc16f29.pdf

Before replacing the diodes you MUST scrape off the carbonized section of the PCB first because it is conductive and it is subjected to high Voltage.

[Goznu]

Re: Hisense 46K360MN

Awesome. That's great news. Thank you very much for your help. This is such an awesome site, I wouldn't have been able to do all the work on the TVs that I have done without it. I really value the information that I have received on this site, it is a very resourceful place. My goto place, actually. Thanks again.