Hitachi wide screen TV fault ..

[andrewpreece]

Beware, there will probably be a very large electrolytic capacitor inside that is charged to 300V even when the tv is off. It'll be in the power supply area near where the mains comes in. Discharge this capacitor first, best way is to put beefy resistor across the terminals, maybe 100 Ohm, make sure you don't get your fingers involved.

If you don't know what you're about, don't take the risk. NB freezer spray can sometimes find dry joints, or hot air, you can buy appropriate freezer spray then se if you can initiate the fault ( or cure it ) by spraying different areas. Remember the voltages inside a TV can be lethal.

Andy

[T i m]

Hi all,

A mate is about to throw out a 5 yr old Hitachi 28" wide screen TV with what he has been told by a couple of TV engineers ( I think just from his description) as having a 'known fault' and an 80 pound 'panel change' would be the cure?

He says all might be well, then the set turns off and may come straight back on from the remote, or take some time or not come back on at all.

If this fault is known and 'fixable' by a reasonably confident electronics engineer (me, given the right parts and a prod in the right direction ) I might take it and fix it for my Mum and Dad?

Any thoughts please?

All the best ..

T i m

keeping the 17 year old Sony 18" monitor style TV going ... ;-)

[Brian Reay]

Sounds like a classic 'dry joint' problem- probably in the standby PSU area. Got to be worth a try.

May be worth trying to get a manual- not sure on the Hitachi ones but some TV ones have very good flowcharts to common faults. OK, not needed to find the fault but it can make it VERY quick- I had a similar fault on another make, flow chart helped me find it in less time than the soldering iron took to heat up.

[logized]

If you can find out the model number, you may be able to find the symptom in this repair database see -

[T i m]

Hi Brian .. it has indeed .. I sorted a mates Sony DVD surround sound unit the other day .. loads of ribbon cables and digital complicated stuff .. fault was a dry joint where the tin 'cable' joined between the o/p PCB and the speaker plug socket .. ;-)

My mate is bringing in the owners manual tomorrow .. might need the real service manual though .. I have a mate that used to be in TV repairs ... (now an animal warden for the local council ...) ?

OK, not needed to find

Result!

Thanks ..

T i m

[T i m]

Well I'm no TV engineer (Datacomms mainly) but I've been near enough sw mode PSU's to have a healthy respect for such stuff (but thanks for the reminder) ;-)

NB freezer spray

I need to get some more of that .. BT used to supply me with it 25 years ago ... ;-(

or hot air,

Yep, still got my hot air gun .. handy for heat shrink ;-)

you can buy appropriate freezer

And work with one hand in my pocket ... ;-)

Thanks again Andy .. I'll let you all know what I find (if it get's that far)

T i m

[T i m]

..

T i m

[T i m]

Hi again Brian ..

Forgot my sig ..

A lowly G7 here (mainly 'packet' before cheap internet)

I was considering getting my daughter into the 'Novice licence' .. is that still going?

Cheers ..

T i m

the email works ..

[raden]

In message , T i m writes

The plumbing stuff is cheaper

[Dave Plowman (News)]

Sounds like a SMPS fault. With some, it's easier to simply change the lot. Philips did a kit of ICs for at least one model with this problem, as it was near impossible to diagnose the actual fault.

[T i m]

Ah, good idea .. B&Q here I come ;-)

Cheers ..

T i m

[T i m]

Ah, ok, well if its that and the kit is cheap enough (and not big SM devices) I don't mind giving it a go ..?

I should get the model no today so we can go from there ..

All the best Dave ..

T i m

[Dave Plowman (News)]

They might well do an exchange board or repair kit if it's a common one.

Problem with those clever SMPS is they shut down with a fault, or won't power up with one - or no load - which makes finding it tricky.

[sPoNiX]

If you post the model number and a description of the fault here:

someone may be able to point you to the exact cause of the fault.

sPoNiX

[T i m]

Swines!

I used to work on a particular data-comms box that had a logic 'loop' that was also a b*****d to fault find. Break the loop to fault find and it stops working anyway .. ;-(

T i m

[T i m]

Done (thanks for that)

I now know it's a Hitachi C28W430N (if that means anything to anyone?) and he says it runs ok between 1/2 hour and 6 days!

When it switches off, if they 'lift one corner and drop it slightly' it more often than not works ok ... (that sounds like our 'engineers slap' ).

To me this would point very much to a dry joint and might be located by some subtle tapping (inside) with a bit of dowel and some hot / cold?

All the best ..

T i m

(the problem is there not enough room for the set AND me in this house at the same time ..

[Brian Reay]

Yes and no.

It is now called the Intermediate, gives basically 50W, and all bands. However, there is now a lower level licence that must be taken first, the Foundation Licence. The old Full licence level is being renamed the Advanced.

Check out the links from my website to the training site- full details there and some free study material.

73

-- Brian Reay

FP#898