Hisense F42K20E HDMI inputs not detected

[blazie151]

Hisense F42K20E, no signal message from all HDMI inputs, been pulling my hair out over this one. I checked over the power supply board because I was originally told it wouldn't power on and stay on, no problems found though a couple of voltages seemed like they could be a hair out of range (18v measured 19v, LED voltage was 260v which seemed a little high to me). The brightness setting doesn't seem to change the LED level, and the large cap on that circuit gets pretty warm. Anyway, HDMI inputs display no signal found, can't seem to track down a problem with the main/input board. No caps look bad visually, will be uploading some images with voltage measurements for reference. Also, I tested every SMD fuse I could find and all were good (including inside the coax module in case there was a surge or something). Any help would be appreciated. I don't want to replace this whole board if it's something I can fix.

[blazie151]

Re: Hisense F42K20E HDMI inputs not detected

Found another image for it on SJ that's a little cleaner than mine. Again, I have voltage measurements on my uploads, which are of the exact board in question. Could it be the HDMI switch chip that all 3 HDMI ports are ran to? Is there any way to test it besides just replacing it, can't find what the voltages on the pins should be to test it? PS331 is the number on that chip.

[mmartell]

Re: Hisense F42K20E HDMI inputs not detected

It's that ic or the voltage driving it is missing. The ic''s crap out easy enough so wouldn't surprise me.

[blazie151]

Re: Hisense F42K20E HDMI inputs not detected

It's that ic or the voltage driving it is missing. The ic''s crap out easy enough so wouldn't surprise me.

Any chance you know the voltages on the pins to check for? Then at least I'd know whether it's the IC or something before it. I was looking for that IC in the US and can't find it from anywhere but China, can't wait that long on the part.

[mmartell]

Re: Hisense F42K20E HDMI inputs not detected

Don't know the voltage - does it get hot when powered on ? Harvest the part from another board.

[dick_barton]

Re: Hisense F42K20E HDMI inputs not detected

There's details of the PS331 in the following manual on page 38. It will at least show you the grounds and power supply points.

[CapLeaker]

Re: Hisense F42K20E HDMI inputs not detected

So you have a brightness and an HDMI issue. The main board is probably cheaper to replace than trying to repair it. I would count one plus one together, that your problems may not only be the HDMI switch IC, there could be something wrong with the main IC. Hisense is a El Cheapo brand anyhow, so I wouldn't invest to much time into it, repairing something, that is complicated to repair.
Next thing: On this TV you can also have HDMI / Audio issues, due to a bad EEPROM.

See that list keeps getting longer... A new main board is something like $50-60. If you would be getting all these IC's and caps, shipping and all the jazz, the $ tag would be getting there too. That is just my opinion.

[blazie151]

Re: Hisense F42K20E HDMI inputs not detected

Don't know the voltage - does it get hot when powered on ? Harvest the part from another board.

Doesn't get too warm. Actually might not be heating up at all and just getting residual heat from the trace connections. Don't have a spare board to pull one from, unfortunately. If the chip was in phones or computers I'd have some, but nope. Anyone else happen to have one?

There's details of the PS331 in the following manual on page 38. It will at least show you the grounds and power supply points.

Thank you very much. That will at least let me know which pins should have some sort of voltage and anything from 3v to 5v should be enough to trigger an IC. At least I can somewhat test it by tracking power in and out, and if I'm getting the right power/signal in and not out then I've found my problem for sure.

So you have a brightness and an HDMI issue. The main board is probably cheaper to replace than trying to repair it. I would count one plus one together, that your problems may not only be the HDMI switch IC, there could be something wrong with the main IC. Hisense is a El Cheapo brand anyhow, so I wouldn't invest to much time into it, repairing something, that is complicated to repair.
Next thing: On this TV you can also have HDMI / Audio issues, due to a bad EEPROM.

See that list keeps getting longer... A new main board is something like $50-60. If you would be getting all these IC's and caps, shipping and all the jazz, the $ tag would be getting there too. That is just my opinion.

I didn't realize the EEPROM could cause those issues. Audio works great by the way, so do the AV and Component inputs. Voltage on the LEDS should be 245v and not 260v so there's probably a problem with the cap at (u701?, don't have the power board in front of me atm) but it's a known problem. And then there's the 2 18v that are reading 19.1v, which can cause overheating and other issues. All that is from the power board though so even after a main board swap I'll have additional repairs to do. Cheapest board I found was $60 including shipping, SJ was $70. I found those HDMI switch ICs from China for $9 for 5 of them, so they are pretty cheap, but the time frame is not gonna work. I agree the board might end up being a better solution unless someone on this forum happens to see this and have a spare PS331 laying around they want to send me for $5, cause I found that cap cheap too. But multiple repairs adds up fast and if there's still a problem after that I've wasted time and money, not to mention to possibility that the HDMI switch popped because of an issue like over voltage due to a failed regulator or something. Last night I went on eBay just to check and someone happened to be selling all 3 boards from this TV and I decided to send him a best offer which he accepted, so I have all 3 boards coming to me to repair this. I plan on taking many measurements and may try repairing the old boards to sell after I have working ones for reference and recouping some cost there. If the issues stand out to me that is.

Thank you all for the help, I really appreciate it. If I end up tracking down that it's the HDMI switch IC or something else I'll post, but I'm probably just going to swap the power supply and main boards and call it a day on this one. I'd pop over the IC from the working board just to check but I don't want to risk damaging it. If it wasn't a 0.5mm pitch 50+ pin smd with high failure rate I would. Bismuth aka chip quick works wonders for those, but some smds are more sensitive to heat than they should be and I don't want to risk popping it and having to wait 3 weeks for a part.