misted C electrolyte

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

"N_Cook"

** 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

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.

"mike"

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

As do most PCB cleaner sprays.

** 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

inside

can do

half a

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.

"Nutcase Kook "

** Yes.

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

.... Phil

^

Indeed. But that's not what Mike said.

"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

inside

can do

half a

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

"Nutcase Kook"

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

" 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

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

Sylvia.

Eliminate the Celcius/Fahrenheit confusion by maintaining everything at -40C, AKA -40F.

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

which seems to be almost the same as this Goodmans LD1575D

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.

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 ;-)

"mike"

** And the rest of the civilised world has them calibrated in degrees C. ** See my explanation above - f*****ad.

** Take your hand off it - wanker.

... Phil

At -32F that will be some really cold ice.

-- Cheers, WB .............

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?

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