Recapped Magnavox 42mf531d/37 still no inverter lights

[snake91876]

I have a magnavox 42mf531d/37 lcd . 4 caps were popped on power supply. It would not do nothing. Replaced the three 1500uf 35v caps and the 2200uf 25v and now it sounds like its coming on but still doesnt light back light. I have 24v at the plugs going to each side of the inverter boards but its like somethings not telling them to come on. I can slightly unplug the left board and the backlights begin to flash but wont stay on its like its jumping the voltage to another pin. What direction now.

[tom66]

Re: Recapped Magnavox 42mf531d/37 still no inverter lights

Check BLON, DIM on connector. You have 24V and GND wires, then two wires for the BLON and DIM.

[budm]

Re: Recapped Magnavox 42mf531d/37 still no inverter lights

Also check the caps in both inverter boards, all fuses, especially if it has small black fuse with '15' or '20' on the top. Also inspect the IC and the MOSFETs of both boards.
Chassis number of this TV?

[snake91876]

Re: Recapped Magnavox 42mf531d/37 still no inverter lights

Alright on powersupply voltage on plugs to backlights

Left backlight right backlight

0v von 0v g
0v vdim 0v g
0v g 0v g
0v g 0v g
0v g 0v g
0v g 24v v
0v g 24v v
24v v 24v v
24v v 24v v
24v v 24v v
24v v
24v v

[budm]

Re: Recapped Magnavox 42mf531d/37 still no inverter lights

OK, it is not getting either BL_ON (Von), or the Dimming signal (Vdim) from the main board.
Time for more pictures of the boards.

[snake91876]

Re: Recapped Magnavox 42mf531d/37 still no inverter lights

Here are the pics i did find a smoked place on the cover over the main board it was directly over the black square thing in the bottom middle of picture 5.

[budm]

Re: Recapped Magnavox 42mf531d/37 still no inverter lights

So far I cannot find the service manual for this model, we will need that to troubleshoot the main board. Is there chassis number on the model number sticker tag? Something like Model number xxxxx TPE1.0U-LA

[snake91876]

Re: Recapped Magnavox 42mf531d/37 still no inverter lights

No additional
information was on tag
just the 42mf number.

[tom66]

Re: Recapped Magnavox 42mf531d/37 still no inverter lights

Can we see the tag? Very strange if that is the case.

[tom66]

Re: Recapped Magnavox 42mf531d/37 still no inverter lights

One other thing, those axial lead Nichicon are not low esr so not suitable for the PSU. Not going to be a problem yet (24V is good) but may be a problem when under load or after the caps have aged.

[snake91876]

Re: Recapped Magnavox 42mf531d/37 still no inverter lights

Where is the tag located you want to see.

[tom66]

Re: Recapped Magnavox 42mf531d/37 still no inverter lights

The tag which you state only has the model. It may be in a different encoding.

[RON_CET]

Re: Recapped Magnavox 42mf531d/37 still no inverter lights

I have the service data if needed it 's large file I'll be glad to upload or send
also have the panel info just need the information on sticker in set there's about 4 panel version

[snake91876]

Re: Recapped Magnavox 42mf531d/37 still no inverter lights

Here are pics of back of tv cover, and back of lcd panel with the requested information on them.

[RON_CET]

Re: Recapped Magnavox 42mf531d/37 still no inverter lights

Here's the service data from your picture for the panel,also attached is a service bulletin,check make sure your serial number falls within the scope of this bulletin,hope this information helps

[snake91876]

Re: Recapped Magnavox 42mf531d/37 still no inverter lights

Not that familiar with surface soldering, repalcing these things fix the signal power to the inverter boards.

[snake91876]

Re: Recapped Magnavox 42mf531d/37 still no inverter lights

I have just noticed this repair is for a 42mf231d/37 and i have a 531d so this
would not apply to my unit.

[snake91876]

Re: Recapped Magnavox 42mf531d/37 still no inverter lights

I have checked diodes on power supply none were shorted except one that was setting the meter off both ways , i took it out of the board and it tested normal i guess its in a parallell or something. Anyway diodes seem to be ok.

[tom66]

Re: Recapped Magnavox 42mf531d/37 still no inverter lights

Well, you have 24V, problem is not on PSU...
VON is your problem, so mainboard has to be considered.

[snake91876]

Re: Recapped Magnavox 42mf531d/37 still no inverter lights

Well i know that the main board had a couple of smoked spots so i may have to try another board. thanks