Tosiba 37CV5050D, Sound but no Picture

[keithf2]

Have just bought this TV from a Auction, Main Board Toshiba PE0535 V28A000709B1. Power Board PE0531 V28A000711B1.
Plug P861 ,24volts ok at 24volts.
Connected to the mains and Ariel. Got the sound ok, but no picture, and could not see any backlights.

[tom66]

Re: Tosiba 37CV5050D, Sound but no Picture

Check BL ON signal on inverter.

[kburks1230]

Re: Tosiba 37CV5050D, Sound but no Picture

Could a bad ysus give no picture and still not cause short protection relay looping?

[tom66]

Re: Tosiba 37CV5050D, Sound but no Picture

Not on a 37" LCD TV.

[keithf2]

Re: Tosiba 37CV5050D, Sound but no Picture

Checked the Inverter Board,PPW-EE37VT-0.
CN1
Pin 1 to 5, +24v,OK.
Pin 6 to 10, OK.
Pin 11, VBR-A, did not check.
Pin 12, On/Off, -19v.
Pin 13, did not check.
Pin 14, Status, -22v.
Could not find any voltages on the transformers, could not find any shorts to deck.
I did some picture but did not come out very good.

[budm]

Re: Tosiba 37CV5050D, Sound but no Picture

"Pin 12, On/Off, -19v." That does not look right, I expect around 3V or so for the ON/OFF (or BL_ON).

[keithf2]

Re: Tosiba 37CV5050D, Sound but no Picture

update on the Readings on the
CN1
Pin 11, VBR-A,0.3v
Pin 12, ON/OFF, 4.9v
Pin 13, VBR, 0.0v.
Pin 14, Status,1.9v


Also ran the screen of this Toshiba from another Toshiba with a working screen, when the screen litup. Checked on the mother board on the connecter to the inverter, that was also 4.9volts.

[tom66]

Re: Tosiba 37CV5050D, Sound but no Picture

The ON/OFF is present, 24V is present, so I'd look at the inverter board, check any fuses and make sure all connectors are seated well.

[keithf2]

Re: Tosiba 37CV5050D, Sound but no Picture

Looks like it may be the main board

[tom66]

Re: Tosiba 37CV5050D, Sound but no Picture

I almost completely disagree. You have BL ON so probably not. Though the VBR is low, it may be because panel brightness is set low.

[aaronwt6]

Re: Tosiba 37CV5050D, Sound but no Picture

Have you tried shining a flashlight on the screen to see if you can make out an image at all? At least the no signal message or something? I agree with Tom 100% on the backlight thing but that would at least prove that you don't have multiple issues before you start buying parts.

[budm]

Re: Tosiba 37CV5050D, Sound but no Picture

Pin 11, VBR-A,0.3v This is an Analog Dimming signal, 0~5VDC (5V = MAX Brightness)
Pin 12, ON/OFF, 4.9v
Pin 13, VBR, 0.0v. This is more likely to be PWM Dimming, 200Hz or so with variable pulse width. Is there a wire connected to this pin. iF it stuck LOW, then the backlights will not be on.
Pin 14, Status,1.9v

Bettr pictures of the boards? Inverter board pictures?

[tom66]

Re: Tosiba 37CV5050D, Sound but no Picture

Most inverters I have seen 0V DC brightness just means minimum brightness (10~15% or so)

[keithf2]

Re: Tosiba 37CV5050D, Sound but no Picture

what about BL ON being 4.9volts

[tom66]

Re: Tosiba 37CV5050D, Sound but no Picture

That's good. Any more than 2V is fine.

[budm]

Re: Tosiba 37CV5050D, Sound but no Picture

VBR-A is the ANALOG dimming, not sure if this TV uses Analog dimming on pin 11, or it uses PWM dimming on PIN 13.

[keithf2]

Re: Tosiba 37CV5050D, Sound but no Picture

So where do we go from here.

[tom66]

Re: Tosiba 37CV5050D, Sound but no Picture

Picture of the inverter board please?

[keithf2]

Re: Tosiba 37CV5050D, Sound but no Picture

Find attached three pictures of the backlight inverter board. On pict2 have tried to hightlight 2 components, do you know what they are for.

[tom66]

Re: Tosiba 37CV5050D, Sound but no Picture

Can you check fuse F1 marked 15A/65V is not blown. Use the ohms range, expecting a reading under 2 ohms with a digital multimeter.