hitachi l40c205

[lrr250r]

Re: hitachi l40c205

Ok i see the sw pin.headed out with the wife i will meter it when i get home...ill post a pic of the touch board. Thank you all for helping.

[tom66]

Re: hitachi l40c205

It may also be STB pin. SW might be for backlight.

[lrr250r]

Re: hitachi l40c205

Ok plugged all the connectors in. STB shows 2.09 volts and doesn't change when i "touch" power. Sw still shows no voltage. The mainboard is a rsag7.820.2107/ROH ver b. Any diagnostics I can run on the main board. I'll get part number off touch board and post a pic after supper.

[tom66]

Re: hitachi l40c205

I would look at the main board then as the cause of the fault. For now we can assume the power supply is OK, it is doing what it is supposed to, as it is not getting any control signal.

Can you show us some pictures of the main board? - it's the one with the video inputs on it.

[lrr250r]

Re: hitachi l40c205

post 18......let me know if ya need better shots of it.....ill pull it out in a few.

[lrr250r]

Re: hitachi l40c205

Mainboard.

[lrr250r]

Re: hitachi l40c205

let me know if ya need better shots or need to see a different area of board.

[tom66]

Re: hitachi l40c205

They're fine...

I've highlighted some voltage regulators with a red dot.

Set the board up in the TV and connect everything. Plug it in.

Set your DMM to 20V DC. Place the black probe in the frame/chassis of the TV or other good ground point. Touch your meter on each leg of the regulator, including the big tab. Note down the voltage reading, along with the identifier (for example "U7" or "IC33") and part code (for example "UMC1117-33".) Post your results; we're looking for a regulator whose output is too low.

[lrr250r]

Re: hitachi l40c205

This is the only one that has any voltage. I get the numbers in a few.

[tom66]

Re: hitachi l40c205

The regulator seems fine. The others - all pins measure zero or nearly zero? (<0.5V)

Is there any way to remove that metal shield on the board or is it soldered down?

[lrr250r]

Re: hitachi l40c205

its soldered but i will remove it. ill recheck volts. Did you see pics of damage to orig power suppl1y ?

[lrr250r]

Re: hitachi l40c205

yes all pivs other than them are zero or nearly......2 show .02 volts

[tom66]

Re: hitachi l40c205

Could be a power surge or something like that hit it - seems surprisingly common in the US. I have never seen it in the UK.

It might be that you just need a new main board - the main processor could have taken a zap.

[lrr250r]

Re: hitachi l40c205

Under the shield

[tom66]

Re: hitachi l40c205

OK, there is a switching power supply on the main board. It generates the power for the CPU. Check the voltage at the single pin I've indicated. Place the black probe in the chassis again for this test.

I don't know for sure what you should measure, but I'd guess from 1.2V to 1.8V.

[lrr250r]

Re: hitachi l40c205

0 volts

[lrr250r]

Re: hitachi l40c205

Touch board

[tom66]

Re: hitachi l40c205

OK, check this too. Maybe it's not getting any input voltage.

I suppose it could be the touch board. I will see if I can get schematics for this and figure out the right pin to jump to turn the set on.

[lrr250r]

Re: hitachi l40c205

.02 volts

[lrr250r]

Re: hitachi l40c205

rsag7.820.1833/roh ver b for the touch board