maxent MX-50HPT51 PS-ON help

[ntehicks]

so I am having a very hard time finding a main board for this model tv. so I wanted to see if I could jumper PS-0n and see if my old mainboard will show full screen. I purchased a used board but seems it is for a 42" model. if someone could tell me how to jumper PS-0n so I can do it without blowing up the tv. thanks so much.

[tom66]

Re: maxent MX-50HPT51 PS-ON help

Usually a 1kohm resistor from 5V to PSON is used.

Note that a bad mainboard which isn't turning on PSON will also rarely show a picture as it is getting stuck in that part of the boot up phase.

[ntehicks]

Re: maxent MX-50HPT51 PS-ON help

is it possible that I have some voltage regulators that are not working. Or could it be possible to reprogram the 42" board with the 50" software?

[tom66]

Re: maxent MX-50HPT51 PS-ON help

It may be possible. If it's a 42" 720p plasma, it will be 1024x768 whereas the 50" 720p would be 1365x768. It might still work with a picture centred on the top left; it then may be possible to adjust using the service menu. But if the picture is scrambled due to the incorrect resolution, you would be stuck...

[lookimback]

Re: maxent MX-50HPT51 PS-ON help

I'm having a similar issue trying to locate a main board for one of these. I'm wondering if I could get the 42" version, which appears to be the identical board, same numbers, etc., and swap eeproms. It actually works, but once it's turned on, none of the buttons or remote work and after a while the picture gets screwy. I'm thinking that the eeprom swap would work, but if the eeprom is the problem, then I'd be out $70.

[ntehicks]

Re: maxent MX-50HPT51 PS-ON help

I tried swapping the eeprom from my old main board and it didn't work either. I have already sold this for scrap but I was thinking if you were able to get into a service mode you should be able to select the right size of screen

[lookimback]

Re: maxent MX-50HPT51 PS-ON help

I was hoping you were still around. Thank you for the reply. Did you swap just the removable flash module (IC907) or also IC906 which is above it? I'm thinking it would be necessary to swap both.

[ntehicks]

Re: maxent MX-50HPT51 PS-ON help

I just replaced IC 907 that could be why it didn't work.

[lookimback]

Re: maxent MX-50HPT51 PS-ON help

Probably so. I believe there's firmware on the other one. I found some smd electrolytics that seemed a little dodgy on the ESR so I'm going to replace them first. If that doesn't fix it, I think I'm going to try the 42" board and switch both eeproms. Thank you for the info, it definitely helps.

[ntehicks]

Re: maxent MX-50HPT51 PS-ON help

I still have the old board.

[lookimback]

Re: maxent MX-50HPT51 PS-ON help

The 50" or the 42"?

[ntehicks]

Re: maxent MX-50HPT51 PS-ON help

it was for the 50"

[lookimback]

Re: maxent MX-50HPT51 PS-ON help

Well, I think I fixed it. I replaced about 15 smd electrolytic caps and 4 through hole ones, all on the main board. All had very high esr. It's working so far. I've had a test video playing on continuous loop for several hours and have had no problems. Remote and key buttons are all fine too. I plan on thoroughly testing it before letting the owner come get it though.

[lookimback]

Re: maxent MX-50HPT51 PS-ON help

Here's an update. My success was short lived. After putting the TV back together, it would only work for about an hour and then none of the buttons or remote would work. I found more bad caps, replaced them, still the same. I think it made a bit of a difference, and I'm still convinced it was bad caps because originally the buttons and remote wouldn't work at all after powering it on. Finally, I bought the board for the 42" and left the TV on with it overnight. Of course, the picture didn't fill the entire screen, and HDMI would just give me a black screen so I used PC , but all I wanted was to see if the buttons and remote would continue to work after it got hot. They did. So, I tried what I spoke about earlier. I swapped eeproms, although I've been told it's a flash chip, not an eeprom. I first tried swapping both the removable one and also the soldered one and it wouldn't power on at all. Then I put the original removable one back in and it works. The firmware now says it's the 50" version. I guess the removable chip must be matched to the individual board. I lost 1 pad during the swap and I used a short piece of heavy insulated 35awg magnet wire from the via on the bottom, up through another via and soldered it to the pin. So far, it's working great. Sure would have been easier if I could have just reflashed the chip without pulling it, but then I wouldn't know this can be done.