Sharp LC-37HV4E takes many attempts before it turns on?

[Dang]

So I've had this Tv for a good while now, I've tried changing the main board/T-con(all in one) and it's still the same. It seems it's a lamp malfunction as I have to go into the service menu, which I can't see, and reset it after five times, I just remember what to press. I've had a good look over the PSU for any dry joints and I couldn't find any, I've tried a hair dryer on certain parts to see if this would spark it into life but no.

I'll take some pictures soon to show where everything is. By the way, this has a media box and I'm quite sure this is fine, considering the lamp fault code it has to be the monitor.

[tom66]

Re: Sharp LC-37HV4E takes many attempts before it turns on?

Are the bulbs pink when it first powers on?

[Dang]

Re: Sharp LC-37HV4E takes many attempts before it turns on?

Are the bulbs pink when it first powers on?

Hi Tom66, not seeing any pink light, upon trying to start it there is nothing, it just spins up the fan, green light comes on and then after about 3 to 4 seconds goes to a constantly flashing red, once every second maybe, eventually it will start but sometimes with vertical white bars, at this point I will leave it to properly warm up for 10 minutes or so before switching it off and back on again, after this it works well for the time that it's on.

I think it's possibly a start up voltage issue top left inverter board(yet to measure voltages) I can't find a service manual which would really help.

[Dang]

Re: Sharp LC-37HV4E takes many attempts before it turns on?

Here's a view of the Tv now on with the associated first time switch on picture distortion.

[selldoor]

Re: Sharp LC-37HV4E takes many attempts before it turns on?

electrotanya?

[Dang]

Re: Sharp LC-37HV4E takes many attempts before it turns on?

electrotanya?

Thank you, very helpful.

[Dang]

Re: Sharp LC-37HV4E takes many attempts before it turns on?

Here are the voltages coming off CN4101 to the top left inverter,
starting PIN 1(top) they measure:

1) 0v
2) 4.3v
3) 14.1v
4) 14.1v
5) 4.9v

Main board voltages from PSU starting PIN 1(left side) of CN3701 are:

1) 0v
2) 0v
3) 0v
4) 5.83v
5) 0v
6) 14.78v
7) 0v

Seems it should be a 15v feed going by the service menu so seems in spec, looks like something specific to the inverters or CCFLs.

[Dang]

Re: Sharp LC-37HV4E takes many attempts before it turns on?

Tried doing what it says for "back light does not light up" and all voltages seem fine on both connectors to inverters 1 and 3, I'm at a loss, any help grwatly appreciated, thanks, Andy.

[Dang]

Re: Sharp LC-37HV4E takes many attempts before it turns on?

Any ideas peeps? I'm just staring at it, it's staring back at me, a blank look in both our faces???????

[tom66]

Re: Sharp LC-37HV4E takes many attempts before it turns on?

I don't have any immediate suggestions except the 1st pic screams main board fault.

[Dang]

Re: Sharp LC-37HV4E takes many attempts before it turns on?

I don't have any immediate suggestions except the 1st pic screams main board fault.

It seems so but I think it's a power issue, I can warm up the main board just over IC4109 and it will power up almost straight away, I'll then cool that area and it's the usual. It's possibly a bad aluminium cap or the feed from the PSU is not right somehow, it's exactly the same as the old main board, that screen distortion is just a symptom of, warming the area in question dosen't produce that screen at all. Going by the above, do you have any ideas? I'm going to look at the main board schematic and see what the voltages should be to see if any are too low. My guess is there's a return voltage that it asks for that gives the go ahead for inverter start up, it's possibly not detecting it or it's just a little low.

[tom66]

Re: Sharp LC-37HV4E takes many attempts before it turns on?

Pic of cap and that area? Do you have service manual with schematics?

[Dang]

Re: Sharp LC-37HV4E takes many attempts before it turns on?

Pic of cap and that area? Do you have service manual with schematics?

Unfortunately no schematic, what I thought I had wasn't there, anyway, here's the photo:

[Dang]

Re: Sharp LC-37HV4E takes many attempts before it turns on?

So I've measured the voltages of the above IC and the pins that correspond to the start up voltages @CN4101, when the IC is cold PIN 1 shows a spike of 14v dropping to a stable 12v and here it will hover until it shuts down, I see about 7.5v at PIN 3, PIN 4 shows nothing with PIN 5 at 4.9v, once this IC is warmed up via a hair dryer, the Tv will now start and I get and additional voltage now at PIN 4 of 7.5v with PIN one raising to 18v, also the start up voltages found at PIN 3 and 4 at connector CN4101 have now dropped away to zero, PSU still as normal. My question is, by warming up the IC it's obviously allowing a signal back through, I guess it's the inv/lamp check signal, is there a way to bypass this need, maybe a shorting of two points on the board? I see that this can be done in some instances, just not so sure how here, thanks again, Andy.

[tom66]

Re: Sharp LC-37HV4E takes many attempts before it turns on?

I think it's more likely that's a DC-DC converter for some internal voltage rail...

[Ltank]

Re: Sharp LC-37HV4E takes many attempts before it turns on?

Service Manual With Schematics