Hitachi 42LDF30U RANDOM SWITCHING OFF

[shepp]

HI ALL, has anyone had this problem, randomly shuts off, aint had a chance to fully test the fault yet but had the back off to see if there where any bad caps bulging

see pics below

[tom66]

Re: Hitachi 42LDF30U RANDOM SWITCHING OFF

Another Vestel you've got there, definitely a later model.

From what I recall the 17PW26 PSU's tend to get bad poly caps like on the 17PW20's/17PW15's.

[shepp]

Re: Hitachi 42LDF30U RANDOM SWITCHING OFF

I keep getting these just recently, I'm watching the tv now waiting for the fault...but it hasn't gone off yet, I might just change all the caps including the polys then, just for peace of mind.

It's a nice tv but to say it's full 1080p the picture is not that great compared to my LG 1080i , I am watching a none HD channel though.

I paid £65 for it so not a bad buy suppose

[tom66]

Re: Hitachi 42LDF30U RANDOM SWITCHING OFF

£65 is quite steep for a 42" 1080p I got a 40" 1080p Samsung for £40. But anyway check the voltage rails before & after fault, see if something drops out.

[shepp]

Re: Hitachi 42LDF30U RANDOM SWITCHING OFF

It still hasn't faulted yet....it's been on nearly an hour, I haven't actually witnessed the fault it's just what the guy said, but I'll keep testing and see what happens, will report back tomorrow

[tom66]

Re: Hitachi 42LDF30U RANDOM SWITCHING OFF

It still hasn't faulted yet....it's been on nearly an hour, I haven't actually witnessed the fault it's just what the guy said, but I'll keep testing and see what happens, will report back tomorrow

I had a Vestel which just had a loose connector, reseated that and no more random power offs, lasted a whole 48 hour burn in test.

[shepp]

Re: Hitachi 42LDF30U RANDOM SWITCHING OFF

When I took the back off I did reseat all the plugs, and some screws had broke the mounts off as if it's been dropped but no marks anywhere, so might have fixed it without doing much....lol

I'll just test it for a few days and see what happens then

[shepp]

Re: Hitachi 42LDF30U RANDOM SWITCHING OFF

New this one would come back to bite me in the ass!

Tested it and was fine...sold it and 5 days later its coming back.....keeps switching off and picture scrambling, SO LOOKS LIKE ILL BE DOING YOUR SUGGESTION TOM AND SEEING WHAT DROPS OUT WHEN FAULT APPEARS....IF I CAN GET IT TO FAULT.......LOL

[multimeter]

Re: Hitachi 42LDF30U RANDOM SWITCHING OFF

vestals also suffer badly from cold joints,i fixed one that had 14 cold joints on it,you could actually wiggle capacitors and the legs would move on the solder side!,check for that as well.

[shepp]

Re: Hitachi 42LDF30U RANDOM SWITCHING OFF

ive got it now on test to see what happens and its not done anything yet ive wiggled stuff about and its still ok...only been on for 30 minutes so far tho

if it still does nothing i will get the soldering iron out and change some caps and check the board for bad joints

[shepp]

Re: Hitachi 42LDF30U RANDOM SWITCHING OFF

i had it through HDMI so im switching to scart now see what happens, if it does start messing up does that mean the main board is dodgy...because the pictures fine through HDMI??

[multimeter]

Re: Hitachi 42LDF30U RANDOM SWITCHING OFF

bear in mind ,when components get tested,and they confirm ok,it still dosent mean they are ok,they can and will breakdown under a load,quite hard to pinpoint intermittant faults like these,further back in this thread tom 66 suggested testing the voltages before and when the fault happens (if) it happens,then you can trace back along and test components on that rail ,,if it was me ,i would heat up the board on the solder side of the psu at certain points,if fault then occurs again,hit the same spot with freeze spray,problem may well disappear ,this at least will rule out cold joints.this is screaming a cold joint.another trick would be to flex the psu in a very dark room with a plastic rod or simular,with the tv power on,this might show a tiny spark leading to a failed joint also.

[shepp]

Re: Hitachi 42LDF30U RANDOM SWITCHING OFF

bear in mind ,when components get tested,and they confirm ok,it still dosent mean they are ok,they can and will breakdown under a load,quite hard to pinpoint intermittant faults like these,further back in this thread tom 66 suggested testing the voltages before and when the fault happens (if) it happens,then you can trace back along and test components on that rail ,,if it was me ,i would heat up the board on the solder side of the psu at certain points,if fault then occurs again,hit the same spot with freeze spray,problem may well disappear ,this at least will rule out cold joints.this is screaming a cold joint.another trick would be to flex the psu in a very dark room with a plastic rod or simular,with the tv power on,this might show a tiny spark leading to a failed joint also.

the problem is im not getting the fault here... but will try that and see what happens

thanks multimeter

[multimeter]

Re: Hitachi 42LDF30U RANDOM SWITCHING OFF

at which points on what circuit board were the screw mounts broken off?i also would be checking circuit traces point to point for continuity ,if the tv took a twist when dropped ,so will the boards...

[shepp]

Re: Hitachi 42LDF30U RANDOM SWITCHING OFF

at which points on what circuit board were the screw mounts broken off?i also would be checking circuit traces point to point for continuity ,if the tv took a twist when dropped ,so will the boards...

it was at the bottom were the cover fastens on, ive checked there, ive just changed some caps coz they look suspect, but when i took them out they looked ok, replaced anyway, but then when i switched tv back on it did the fault, i checked voltages going to main board and they all seemed stable, so for a wild guess i would say its something on the main board?

[multimeter]

Re: Hitachi 42LDF30U RANDOM SWITCHING OFF

if psu turns out ok,assuming when the fault occurs again that is,then i would be checking the voltage regulators on the main board that supply a voltage to the t con board,one of your symptoms is a scrambled picture when the fault happens,the t con might be loosing power,the main board senses it then shuts down the psu

[shepp]

Re: Hitachi 42LDF30U RANDOM SWITCHING OFF

if psu turns out ok,assuming when the fault occurs again that is,then i would be checking the voltage regulators on the main board that supply a voltage to the t con board,one of your symptoms is a scrambled picture when the fault happens,the t con might be loosing power,the main board senses it then shuts down the psu

tested again and voltages are stabble when fault occurs, with the sound switching off before the picture goes....ive ordered a main board for it for £20 but its not come yet, so fingers crossed thats the culprit, i should get it tomoz so will update when ive retested it

what voltage does the t-con run on??

[tom66]

Re: Hitachi 42LDF30U RANDOM SWITCHING OFF

tested again and voltages are stabble when fault occurs, with the sound switching off before the picture goes....ive ordered a main board for it for £20 but its not come yet, so fingers crossed thats the culprit, i should get it tomoz so will update when ive retested it

what voltage does the t-con run on??

Usually 5V for T-con.

Try using some contact cleaner on the side button board... sounds like it is controlled switching off.

[shepp]

Re: Hitachi 42LDF30U RANDOM SWITCHING OFF

board came today and its got the wrong t-con connector on it....and i cant find the right board....so im screwed now! gonna have to refund them, now im left with a 42" thats useless

major bummer!

[multimeter]

Re: Hitachi 42LDF30U RANDOM SWITCHING OFF

board came today and its got the wrong t-con connector on it....and i cant find the right board....so im screwed now! gonna have to refund them, now im left with a 42" thats useless

major bummer!

will they not take returns? some do,worth a try,do keep an eye on revision numbers on the board they do vary