misted C electrolyte

[N_Cook]

LCD TV SMPS LV C vented electrolyte, seemingly evenly over the whole inside
of the TV and over all the boards. Leave in place? , wash off as best can do
with methylated spirits or something?. Otherwise the TV works of for half a
second before it decides not enough power available.

 

[N_Cook]

This is Goodmans LD1575D. In passing I see a 1W 4M7 R under the SMPS Tx with
the opto coupler, never seen that before , connecting mains side to
secondaries side

 

[Phil Allison]

"N_Cook"

This is Goodmans LD1575D. In passing I see a 1W 4M7 R under the SMPS Tx
with
the opto coupler, never seen that before , connecting mains side to
secondaries side

** That 4M7 resistor protects the SMPS tranny from insulation breakdown due
to a high static voltage building up on the antenna in dry, windy weather.

It's a specially rated part for the job.

Class 2 rules allow it.


..... Phil

 

[mike]

LCD TV SMPS LV C vented electrolyte, seemingly evenly over the whole inside
of the TV and over all the boards. Leave in place? , wash off as best can do
with methylated spirits or something?. Otherwise the TV works of for half a
second before it decides not enough power available.

I've fixed a bunch of Tek Scopes with this problem.
The electrolyte is VERY corrosive. If you leave it there, it will eat the
pcb traces and anything else it gets on.

Clean it WELL with something like Simple Green. Use a toothbrush
and get it out from between chip pins, under chips, inside via holes.
Blow it dry and clean it again.
Then do it twice with high-concentration alcohol, like the 99% stuff
you can get a the drugstore.
Then dry it as hot as you can without breaking the parts.
150F is reasonable.

Of course, you need to remove or protect any parts that can't get wet.
Good luck.

 

[Phil Allison]

"mike"

Clean it WELL with something like Simple Green. Use a toothbrush
and get it out from between chip pins, under chips, inside via holes.
Blow it dry and clean it again.
Then do it twice with high-concentration alcohol, like the 99% stuff
you can get a the drugstore.

** De-natured alcohol " (Methylated Spirits ) works fines to.

As do most PCB cleaner sprays.

Then dry it as hot as you can without breaking the parts.
150F is reasonable.

** 150C is highly unreasonable.

It will destroy electros, melt some plastics and harm some semis.

100C should be the absolute limit.

70C will do the job quickly.


.... Phil

 

[N_Cook]

I've fixed a bunch of Tek Scopes with this problem.
The electrolyte is VERY corrosive. If you leave it there, it will eat the
pcb traces and anything else it gets on.

Clean it WELL with something like Simple Green. Use a toothbrush
and get it out from between chip pins, under chips, inside via holes.
Blow it dry and clean it again.
Then do it twice with high-concentration alcohol, like the 99% stuff
you can get a the drugstore.
Then dry it as hot as you can without breaking the parts.
150F is reasonable.

Of course, you need to remove or protect any parts that can't get wet.
Good luck.

Is all C electrolyte corrossive? This looks like cod liver oil in colour and
texture , with no hint of corrossion on any surface it is laying on.

 

[Phil Allison]

"Nutcase Kook "

Is all C electrolyte corrosive?

** Yes.

It is also conductive - which can be a bit of a worry around electronics.





..... Phil

 

[JW]

"mike"

** De-natured alcohol " (Methylated Spirits ) works fines to.

As do most PCB cleaner sprays.

^
** 150C is highly unreasonable.

Indeed. But that's not what Mike said.

 

[Phil Allison]

"JW"
"Phil Allison"

"mike"


Indeed. But that's not what Mike said.

** Fair enough.

Guess us engineering types are not used to seeing obsolete Fahrenheit temps
used in electronics.

Boiling water = 212 F

Freezing water = -32F

and paper burns at Fahrenheit 451 ....



..... Phil

 

[N_Cook]

I've fixed a bunch of Tek Scopes with this problem.
The electrolyte is VERY corrosive. If you leave it there, it will eat the
pcb traces and anything else it gets on.

Clean it WELL with something like Simple Green. Use a toothbrush
and get it out from between chip pins, under chips, inside via holes.
Blow it dry and clean it again.
Then do it twice with high-concentration alcohol, like the 99% stuff
you can get a the drugstore.
Then dry it as hot as you can without breaking the parts.
150F is reasonable.

Of course, you need to remove or protect any parts that can't get wet.
Good luck.

pH of 5 this yellow oily stuff, not conductive as far as paper soaked in it
, 0.5mm probe tip separation and >30M

 

[Phil Allison]

"Nutcase Kook"

pH of 5 this yellow oily stuff, not conductive as far as paper soaked in
it
, 0.5mm probe tip separation and >30M

** What you have there sonny is " Ethylene Glycol" - ie what remains of
the electrolyte after all the water has boiled off.

http://en.wikipedia.org/wiki/Ethylene_glycol

" Ethylene glycol (IUPAC name: ethane-1,2-diol) is an organic compound
widely used as an automotive antifreeze and a precursor to polymers. In its
pure form, it is an odourless, colourless, syrupy, sweet-tasting liquid.
Ethylene glycol is toxic, and ingestion can result in death. "

Without any water, it is a non conductor.

But don't worry, it will absorb it from the air on any humid day.

Taste sweet does it ..............



..... Phil

 

[Sylvia Else]

"JW"
"Phil Allison"


** Fair enough.

Will you stop trying to impersonate Phil - you're no good at it anyway.

Sylvia.

 

[mike]

"JW"
"Phil Allison"


** Fair enough.

Guess us engineering types are not used to seeing obsolete Fahrenheit temps
used in electronics.

Boiling water = 212 F

Freezing water = -32F

and paper burns at Fahrenheit 451 ....



.... Phil

Well, here in the us of a, the typical kitchen oven, which is what
most people have to dry a board, is calibrated in F.

FWIW, probably true for most here...but the few GOOD engineering
types READ what is written instead of jumping
to conclusions and mouthing off with "that" tone of superiority.

 

[mike]

looks as though all this elecrolyte was a bum steer, leaking yes, but not
reason for failure. Will have to go in deeper . Puting in the pair of
Fairchild backlight inverter IC numbers into Google - led to a French
repair forum with a pic of the ps of a Toshiba
teleservice.xooit.fr/t4944-platine-alim-toshiba.htm
and then schematic
http://elektrotanya.com/toshiba_15v330dg.pdf/download.html
which seems to be almost the same as this Goodmans LD1575D

You seem to be looking for a way to ignore the cleaning issue.
I've had TEK circuit boards that I'd cleaned "squeaky clean",
TWICE. But it took a third time to make the board come back to
life.
Electrolyte may not be your current problem, but it WILL
be a future problem.
Leave electrolyte on stuff at your peril ;-)

 

[Phil Allison]

"mike"

Phil Allison

Well, here in the us of a, the typical kitchen oven, which is what
most people have to dry a board, is calibrated in F.

** And the rest of the civilised world has them calibrated in degrees C.

FWIW, probably true for most here...but the few GOOD engineering
types READ what is written ..

** See my explanation above - fuckhead.

instead of jumping
to conclusions and mouthing off with "that" tone of superiority.

** Take your hand off it - wanker.


.... Phil

 

[N_Cook]

I reckon the "electrolyte" is kitchen fat. I saked the owner if used in a
kitchen and he said no. But it was used in a caravan which was used for
cooking in. So tried tasting somer on the tip of my tongue and swilling off
soon after. No sweetness , if anything cooking fat taste. Checked my taste
buds with some glycerin and distinct sweet taste. No problems with cracked
tops , ESR or capacity with the removed and then replaced caps.

Cleaned the main board with meths , dried for an hour or so and same
symptoms.
Cleaned the ps and inverter board , dried for only 10 minutes and ps went
into protect.
Dried with hot air and pic flashed up for 1/10 sec or so. Concentrated
heating on the 6 inch long strip of isolated track along the pcb edge to one
of the backlight connectors and now about 1/3 second. Previously about 1
second when I eceived the TV.
Agrees with the owner in that when this problem fisst appeared someone
technical decided to run a hair drier in the top and it ran perfectly on for
a week or so.
Yesterday I picked up at a hamfest a range of 1G to 1T ohm resistors
coincidently. I reckon its a glass fibre osmotic problem and HV , like I've
seen on scope tripler/quint boards over the years.
Will try cutting those long lines and HV cable bridged there instead.
There must be another control line back from the inverter protect system,
back to the main control and then back out to the backlight control to the
inverter.
If this is the failure mechanism then presumably a generic problem for this
sort of long pcb trace to a backlight connector and then cable proper.
Will have to see if there are reports of this problem and delve into
backlight inverter control a bit more.

Again generally, comparing a 15 inch LCD TV to 30 inch. Obviously the
inverter and lights would be x4 power but would anything else in the
electronics be much different?

 

[N_Cook]

problem was with the 3 small 3Kv rated blue ceramic caps at the inverter
output. First variation between this Goodmans and the Toshiba schematic.
Overlay numbering the same , 3KV the same but 3x 5pF on the Toshiba and 2
marked 12 presumably 12pF and one 4.7 presumably 4.7pF. Now to find dome 5KV
rated ones.
Disconnected them and powered up for long enough to get the display on for
some 20 seconds and blue screen with annunciators etc before I decided to
switch off and find some replacements

 

[Phil Allison]

"Nutcase FUCKING KOOK "

I reckon the "electrolyte" is kitchen fat. I saked the owner if used in a
kitchen and he said no. But it was used in a caravan which was used for
cooking in. So tried tasting somer on the tip of my tongue and swilling
off
soon after. No sweetness , if anything cooking fat taste. Checked my taste
buds with some glycerin and distinct sweet taste. No problems with cracked
toor capacity with the removed and then replaced caps.

** Quote:

" LCD TV SMPS LV C vented electrolyte, "


What Low Voltage Cap was that - eh ??????

You fucking LIED to us - AGAIN !!!!!!

You FUCKING MORON !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!





.... Phil

 

[N_Cook]

found a number of 22pF 3KV and seriesed them up , working fine now

 

[N_Cook]

Using principally a 8.5KV transformer and variac and 300M ohm 1000:1 divider
capacitors passed at
1.5KV , 9 to 10uA
2KV , 12 to 14uA
2.5KV , 15 to 17uA
at 50Hz