Proview PL926Wbi, no power

[jetadm123]

Re: Proview PL926Wbi, no power

Diode D28 located right above the voltage regulator, what is that brownish color on it?

[retiredcaps]

Re: Proview PL926Wbi, no power

You can narrow down the problem by disconnecting all your boards and hooking up the ccfls to the power board. Then apply 3V to the BL_ON pin using a CR2032 battery or two AA batteries in series.

If the backlight comes on, then you know the problem is somewhere on the main board. If the backlight does not come on, you know the problem is in the inverter section. If the mosfets are good, it could be the inverter pwm chip?

[maybenever]

Re: Proview PL926Wbi, no power

Diode D28 located right above the voltage regulator, what is that brownish color on it?

Don't know, I'll check it out.

You can narrow down the problem by disconnecting all your boards and hooking up the ccfls to the power board. Then apply 3V to the BL_ON pin using a CR2032 battery or two AA batteries in series.

If the backlight comes on, then you know the problem is somewhere on the main board. If the backlight does not come on, you know the problem is in the inverter section. If the mosfets are good, it could be the inverter pwm chip?

I'll try this ASAP. Thanks.

[selldoor]

Re: Proview PL926Wbi, no power

On the power supply fuse F203 can you test the voltage on each side .
Meter on 20vdc black lead on ground red on each end of fuse. CARE do not touch the heatsink.

[maybenever]

Re: Proview PL926Wbi, no power

On the power supply fuse F203 can you test the voltage on each side .
Meter on 20vdc black lead on ground red on each end of fuse. CARE do not touch the heatsink.

I've checked voltage on both those fuses. I can't remember which is which, but one was 14.5v and the other was 4.98v. I've never checked a "should be" 5v pin that didn't check at least 5.1v to 5.5v. Wonder why this 5v is a little less?

[maybenever]

Re: Proview PL926Wbi, no power

You can narrow down the problem by disconnecting all your boards and hooking up the ccfls to the power board. Then apply 3V to the BL_ON pin using a CR2032 battery or two AA batteries in series.

If the backlight comes on, then you know the problem is somewhere on the main board. If the backlight does not come on, you know the problem is in the inverter section. If the mosfets are good, it could be the inverter pwm chip?

Connected 3v to BL_ON pin and got nothing. Connected 5v to BL_ON pin and got nothing. I'm about ready to remove the good caps off this thing and move on.

[Rtech]

Re: Proview PL926Wbi, no power

Connected 3v to BL_ON pin and got nothing. Connected 5v to BL_ON pin and got nothing. I'm about ready to remove the good caps off this thing and move on.

Perhap a silly question BUT we all make errors occasionally...I assume that when you applied the voltage btween the BL_On pin and GND...you did have the mains Power switched on ??

[maybenever]

Re: Proview PL926Wbi, no power

Perhap a silly question BUT we all make errors occasionally...I assume that when you applied the voltage btween the BL_On pin and GND...you did have the mains Power switched on ??

Yes, I had the AC power cord connected. When I was checking the MOSFETs, I was told to set my mm to 200ohm, but I got out of range readings, I had to go to 20k to get readings, is that right?

Measured mosfets Q5 & Q6, part # K3615 7F. With meter set on 20k, pin 1 to 2 = starts at zero and just keeps climbing, pin 1 to 3 = 5.64, pin 2 to 3 = 2.66. Both parts test the same.

[selldoor]

Re: Proview PL926Wbi, no power

Yes, I had the AC power cord connected. When I was checking the MOSFETs, I was told to set my mm to 200ohm, but I got out of range readings, I had to go to 20k to get readings, is that right?

Yes that is correct. The test is only for shorts so a reading of less than 30
ohms may be a short. More than 200 should be ok so as long as it is over 200 ohms that is all that is required.

[Rtech]

Re: Proview PL926Wbi, no power

Yes, I had the AC power cord connected. When I was checking the MOSFETs, I was told to set my mm to 200ohm, but I got out of range readings, I had to go to 20k to get readings, is that right?

It may be right,BUT I have exactly the same Board,in my case working,and measuring resistance between Pins 1 and 3,on Q5 and Q6,and irrespective of which way around you have the neg and pos leads of your meter,I get in excess of 10KΩ,so suggest you try again !!

[jetadm123]

Re: Proview PL926Wbi, no power

Here's what I see so far:

1) the main doesn't seem to output a constant BL_ON voltage.

2) you can't get the backlights to turn oun even with an external power source.

3) the mosfets are questionable.

4) the power supply seems to output the proper 5V and 12V.

bad ccfl(s)? bad mosfet? short on mainboard?

[maybenever]

Re: Proview PL926Wbi, no power

Here's what I see so far:

1) the main doesn't seem to output a constant BL_ON voltage.

2) you can't get the backlights to turn oun even with an external power source.

3) the mosfets are questionable.

4) the power supply seems to output the proper 5V and 12V.

bad ccfl(s)? bad mosfet? short on mainboard?

Right, maybe all the above. I've got the backlight assy. removed, connected to a working mainboard, no light. Those mosfets, I check them with 200k range on the DMM, 9.8k reading. 20k range, 5.64k reading, that's -lead on pin 1, +lead on pin 3. My meter is good, I can test a 10k resistor on 200k range, I get 9.8k reading, 20k range, I get 9.84k reading, so the meter is working OK, right. It don't make sense to me. Anyway, putting this project in the experence folder and moving on. Thanks to all.

[maybenever]

Re: Proview PL926Wbi, no power

A correction, that "good" board I tested my ccfls with, in fact was not working I guess. It was out of a working monitor with a small problem, so I was going to recap it and put it back together which I did. Before puting the back on, I connected the Proview lamps, I'll be dog, they both work. So now I have working lamps for future testing.