I killed my Hitachi 28" widescreen ;-(

[T i m]

Hi all,

A friend recently gave me a fairly young Hitachi 28" widescreen nicam
TV that he had just got fed up with.

It had an intermittent fault where it would cut out then:

a) restart on it's own ..

b) be turned back on from the remote ..

c) be restarted by lifting the right front corner and dropping it 1".
(he said) ;-(

With the set running, if you tapped the case (flat hand) you saw horiz
noise bars.

I spoke to a few folk (local TV shop, N/G, Ex TV repair man) and a dry
joint was suggested likely "around the PSU etc".

Yesterday I took the main board out and de-re-soldered lots of the
bigger joints (but didn't find anything 'obvious') and re-assembled,
now nothing at all. (I think I might hear a slight 'click' about 10
seconds after turning it on .. degauss maybe?)

So I've killed it <sigh> (I was hoping to give it to my elderly Mum &
Dad) ;-(

My ex TV man might be able to pop round for a quick look at it (in
case I've missed anything obvious) and / or point me towards a TV man
he knows locally.

Its a C28W430N-??? (133 .. from memory)?

Any thoughts please folks?

All the best ..

T i m (London)

 

[Jerry G.]

This can be anything that you did. You may have bridged some traces or
connections, or didn't properly solder some of them. If you made any
bridged connnections or created a critical opened connection, there is
a chance that some other components have been damaged.

If you are not experienced at TV servicing, your best bet would have to
bring the set in to a service center to have it serviced in the first
place. The repair may have not been too expensive to start with.
Jerry G.
======

 

[jakdedert]

This can be anything that you did. You may have bridged some traces or
connections, or didn't properly solder some of them. If you made any
bridged connnections or created a critical opened connection, there is
a chance that some other components have been damaged.

It could be none of the above. He may have disturbed a loose connection
which was in a totally different area. Excellent advice below:

If you are not experienced at TV servicing, your best bet would have
to bring the set in to a service center to have it serviced in the
first place. The repair may have not been too expensive to start with.
Jerry G.
======

jak

 

[T i m]

This can be anything that you did. You may have bridged some traces or
connections,

Possible but I doubt it.. I was 'old school' BT trained and I've never
had a joint fail yet ;-)

or didn't properly solder some of them.

Again, not impossible .. ;-)

If you made any

bridged connnections or created a critical opened connection, there is
a chance that some other components have been damaged.

Indeed, I did do a visual after soldering and didn't touch any of the
finer joints (previous experience tells me it's *more likely* to be
one of the bigger / tin legged / PSU componets if it's a mechanically
intermittent fault?

If you are not experienced at TV servicing, your best bet would have to
bring the set in to a service center to have it serviced in the first
place.

With hindsight maybe. However I have been soldering things for over 35
years and have fixed many a fault with a simple 'investigation'?
However I'm *not* a TV engineer, (my service work was mainly Datacomms
/ Microfilming kit + 100's of 'projects') but was quoted a potential
repair cost of 80 GBP (by the guy who gave it to me), something I
don't have available at the moment? ;-(

The repair may have not been too expensive to start with.

I believe it would of cost me 25 pounds to get someone to even look at
it and it's not a small thing to cart about! ;-(

I have managed to keep my little 18" Sony Trinitron set going for (we
think) 16 years. I've changed the power switch a couple of times, the
HT transformer thing once (HT arching) and a cap that was causing the
teletext to superimpose over the std picture all the time. I used to
ring my TV repair mate and describe the fault, he would tell me what
to change (often from my own parts stock) and drop the bits in if to
me they were 'special', for me to fit.

I was advised to 'just resolder some of the components around the PSU'
and that's what I did. Is it possible that my resoldering may have
allowed an already broken component leg (like on a voltage reg) to
fall away / disconnect further?

All the best and thanks Jerry ..

T i m

p.s. I'm just about to replace a plastic drive worm on my Panasonic
video (again) and recently fixed a mates Sony surround sound system
(dry joint on the speaker output socket). Our washing machine has
stopped tripping the RCD now I've blown the carbon dust out of the
motor with my garage mate's airline (fingers crossed on that one) ;-)

 

[T i m]

It could be none of the above. He may have disturbed a loose connection
which was in a totally different area.

I did check for that .. and was pretty careful when moving stuff
about. I took the main board out and removed it from it's plastic fame
to give me good access all around. I carefully worked on it on my
antistatic mat (mainly so I didn't damage the friends table I was
working on) using my Weller thermostatic soldering station and
de-soldering pump. All the plugs were sized / polarised to make
incorrect re-fitting nearly impossible?

All the best ..

T i m

 

[**THE-RFI-EMI-GUY**]

But do show the repairman what you did because if you don't and if you
did solder short some connections you will drive the poor bastard to the
funny farm trying to figure out the fault!

Possible but I doubt it.. I was 'old school' BT trained and I've never
had a joint fail yet ;-)

or didn't properly solder some of them.

Again, not impossible .. ;-)

If you made any



Indeed, I did do a visual after soldering and didn't touch any of the
finer joints (previous experience tells me it's *more likely* to be
one of the bigger / tin legged / PSU componets if it's a mechanically
intermittent fault?



With hindsight maybe. However I have been soldering things for over 35
years and have fixed many a fault with a simple 'investigation'?
However I'm *not* a TV engineer, (my service work was mainly Datacomms
/ Microfilming kit + 100's of 'projects') but was quoted a potential
repair cost of 80 GBP (by the guy who gave it to me), something I
don't have available at the moment? ;-(

The repair may have not been too expensive to start with.

I believe it would of cost me 25 pounds to get someone to even look at
it and it's not a small thing to cart about! ;-(

I have managed to keep my little 18" Sony Trinitron set going for (we
think) 16 years. I've changed the power switch a couple of times, the
HT transformer thing once (HT arching) and a cap that was causing the
teletext to superimpose over the std picture all the time. I used to
ring my TV repair mate and describe the fault, he would tell me what
to change (often from my own parts stock) and drop the bits in if to
me they were 'special', for me to fit.

I was advised to 'just resolder some of the components around the PSU'
and that's what I did. Is it possible that my resoldering may have
allowed an already broken component leg (like on a voltage reg) to
fall away / disconnect further?

All the best and thanks Jerry ..

T i m

p.s. I'm just about to replace a plastic drive worm on my Panasonic
video (again) and recently fixed a mates Sony surround sound system
(dry joint on the speaker output socket). Our washing machine has
stopped tripping the RCD now I've blown the carbon dust out of the
motor with my garage mate's airline (fingers crossed on that one) ;-)

--
Joe Leikhim K4SAT
"The RFI-EMI-GUY"

The Lost Deep Thoughts By: Jack Handey
Before a mad scientist goes mad, there's probably a time
when he's only partially mad. And this is the time when he's
going to throw his best parties.

 

[T i m]

But do show the repairman what you did because if you don't and if you
did solder short some connections you will drive the poor bastard to the
funny farm trying to figure out the fault!

LOL

Hi Joe (In all modesty I don't think any TV repairman would find fault
with my soldering. I have been doing it too long and am far too
fastidious to let a less than 100% joint 'go') ;-)

But of course, I am an honest bloke and anyone was to look at it now
would be given the full rundown (after all, TV's aren't my 'game') ;-)

I have nothing to hide and further when I am asked to help someone
when they have 'mucked up' their PC I have to give them some credit
for at least 'having a go' ? (after all, isn't that how we learn?).

My logic re this TV was this.

It cost me nothing.
It cost me nothing to try fiixing it myself
It would cost nothing to throw away and I would have lost nothing.
Even if fixed I'm not sure if I have a home for it and don't
particularly want to sell it.

I wouldn't actually chuck it away without at least seeing if I could
get a friendly TV person to take a quick look at it.

All the best ..

T i m G7ICQ

 

[mcare1]

This could have been a nice easy fault

not in the psu,

but there is a metal heat sink down the centre of the pcb, resolder all
of the parts of this only 2 or 3 transistor and a frame ic , normally
dry joint on these parts


if you resoldered the psu just maybe a case of replacing the chopper
transistor and or ic

good luck

 

[LASERandDVDfan]

I did check for that .. and was pretty careful when moving stuff

about. I took the main board out and removed it from it's plastic fame
to give me good access all around

But you still have to factor soldering. If you aren't that great, you will
make mistakes, including some that are only obvious with scrutiny using a
magnifying glass.

Plus, you only soldered big joints. The problem could have been caused by
smaller joints that you may have not paid any attention to. Moving parts
around probably exacerbated the cold joint condition of the existing fault and
might have also created new ones and caused a larger headache. Cold joints can
sometimes be as clear as daylight, but they can also appear just fine to the
naked eye. - Reinhart

 

[LASERandDVDfan]

I was advised to 'just resolder some of the components around the PSU'

and that's what I did. Is it possible that my resoldering may have
allowed an already broken component leg (like on a voltage reg) to
fall away / disconnect further?

Try checking and resoldering, if necessary, parts of the vertical deflection,
horizontal deflection, and syscon.

It sounds like the techs might have indicated other parts besides the power
supply. - Reinhart

 

[T i m]

This could have been a nice easy fault

It still might be! ;-)

not in the psu,

Ok ..

but there is a metal heat sink down the centre of the pcb,

I remember seeing a lasgish one .. I think it was bent though 90 deg?

resolder all

of the parts of this only 2 or 3 transistor and a frame ic , normally
dry joint on these parts

I think I did de/re-solder those .. I could check again .. ?

if you resoldered the psu just maybe a case of replacing the chopper
transistor and or ic

Ok, I'll see what I can spot. It *was* only a primary run-over, a
first pass so to speak.

good luck

Thanks fella .. ;-)

All the best ..

T i m

 

[T i m]

But you still have to factor soldering. If you aren't that great, you will
make mistakes, including some that are only obvious with scrutiny using a
magnifying glass.

Indeed .. no one is generally 100% but when I was in the training
school at BT my 100 termal solder test job was the only one to ever
get 100% and was placed in the display cabinet? I solder as
instinctively as some folk breath and can see / 'feel' when it hasn't
gone well. My daughter was demonstrating similar skills when she was
10. She soldered a Maplin Xmas tree project that contained over 120
LED's and many other compnents and apart from working fist time the
soldering was something many TV engineers (that I have known anyway)
would be proud of ;-)

Plus, you only soldered big joints.

I did ..

The problem could have been caused by

smaller joints that you may have not paid any attention to.

Oh indeed .. but the quality of this assembly was generally very good.
I have seem some dire flow amd hand soldering in my time and this was
in comparison very good. When I was 10 my Mum would bring things home
from the Primary school she helped at, things like transistor radios,
tape players etc. They were given to her to give to me to 'play with '
"We know your Tim likes to take things to pieces etc". More often or
not I would find a broken wire or dry / poor joint (or shorted can on
old transistors) then fix and return them. ;-)

Moving parts

around probably exacerbated the cold joint condition of the existing fault and
might have also created new ones and caused a larger headache.

Indeed ..

Cold joints can

sometimes be as clear as daylight, but they can also appear just fine to the
naked eye.

I completely agree. But from the responses I got from those who know
about such things pointed me toward dry joints on the bigger
components.

Before I started resoldering I did have a gentle tap about with an
insulated screwdriver (shaft and handle) but couldn't pin any
particular area down. I would have preferred a schematic and some test
points but realised this wasn't my area of expertise so did what I
could with the tools / skills I had? Plus there are some nasty
voltages in there and I don't need a 28" TV *that much* ;-)

Had I not managed to divert the thing it would have been in the skip
anyway ..?

All the best and thanks for your time ..

T i m