Magnavox LCD 37mf437/37 chirping

[mr2013e]

Re: Magnavox LCD 37mf437/37 chirping

big cap voltage(at full work of power board)=1.41(sqrt 2) x line voltage
result is DC voltage and for monofaze line voltage

but i dont know for line voltage 120vac in usa , they have 300-370 vdc (at full work) on big cap .
it is not necessary for me.

[tom66]

Re: Magnavox LCD 37mf437/37 chirping

With PFC circuit, voltage is boosted to around 380V DC, with no relation to input AC voltage, in standby it is 1.4xAC voltage because PFC circuit is disabled (low efficiency at low load.)

[budm]

Re: Magnavox LCD 37mf437/37 chirping

Learning about PFC Booster.

[steinless]

Re: Magnavox LCD 37mf437/37 chirping

hey any updates on this? i have the same problem

http://*************/photo/my-images/703/t6wj.jpg/
http://*************/photo/my-images/191/mlle.jpg/

mines is v 3 though,

replaced the caps. looking at the diodes mentioned next. but was thinking to just chuck the whole thing if after the diodes it doesnt work.

mine measures 13 volts output.

have sound, no image.

gecko friend the print board, see the black rusted area. doesnt seem to affect the board though.

[Rio_Grande]

Re: Magnavox LCD 37mf437/37 chirping

I was going to start a new thread but don't have permission. Same tv 47mf437b/37 chirping when it should be powering up, might get a touch of sound or a few seconds of backlight before it stops trying.

I have read several threads where several different caps were changed but none where it concludes that this was a specific part. I am just trying to narrow it down. I would buy a replacement board, but the only ones I can find are 350.00.

I can solder and replace caps, but I am not much use with a multi meter. Not opposed to learning though. We don't have the money to buy a new board and certainly not a new tv.

Any help will be appriciated. .

[topfli8979]

Re: Magnavox LCD 37mf437/37 chirping

Had a buddy with a good working power supply laying around, installed, chirping is still there. So its gotta be the main board.

[elpelado]

Re: Magnavox LCD 37mf437/37 chirping

i fixed mine by buying a kit from ebay and replacing all the parts they sent me on the PSU. it worked out great

[withalligators]

Re: Magnavox LCD 37mf437/37 chirping

Sorry to resurrect an old thread, but my issue is on the same TV and I figured it better that all the info for future reference be in as few a places as possible.

I have the same TV, with power supply 715T2454-2 S/N 07386. It looks a bit different from the other ones I've seen pictured on various threads. For starters, the 3 tall caps at C952, C951, C953 were all PF nichicon caps, and the one at C955 was a VR series Nichicon. The soldering job looked sloppy so not sure if it was a repair job or a revision of sorts.

I had the chirping issue, and replaced the two zener diodes at ZD904 and ZD902 because they were burnt. I also replaced all the other caps (besides the 4 Nichicon and big 450V Capxon one) on the board with the same rating Panasonic or Nichicon ones.

The TV now works, but there is a very high pitched whine when it is plugged in, and slowly dissipates after it is unplugged.

I'd like to sell this TV, but don't want to sell something that might crap out. What else can I replace to make this thing bulletproof?

Cheers,
Alex

[withalligators]

Re: Magnavox LCD 37mf437/37 chirping

Bump, any ideas?

[plbproductions]

Re: Magnavox LCD 37mf437/37 chirping

I have a a 37" lc370wx1 and when i got it i it would turn off and on i open up and found someone replaced the 2200uf 45v cap badly i resoldier it and it work for about 10 minutes then quit again the power light stayed green and ever 15 secods the inverter board would ight the screen flicker then shut off. i replaced all the caps on the board execept the 45v 2.2uf still the same thing so i replaced that cap with a 2.2uf 450 v cap and now it doesn't flicker but the inverter board still light up every 15 seconds and power light still solid green the board is like the first picture posted on page one.

[jdkruse]

Re: Magnavox LCD 37mf437/37 chirping

I know this is a old thread but I have a 47mf437B/37 replace the four caps and still have chirping and no power. which diodes should i replace?

[withalligators]

Re: Magnavox LCD 37mf437/37 chirping

See my post (#28) just a few above yours. I detail what I replaced to get it working pretty well. Still had a bit of a high pitched whine, but it got better with time.