Planar PL1700-BK - backlights go out

[uligli]

Re: Planar PL1700-BK - backlights go out

Great photos. I'm jealous that I can see grass in the background. Here I just finished shoveling snow and it is piled about 2 feet on one side. Anyone still playing Beach Volleyball on Daytona Beach?

That remembers me back in the 90's when i rent a volleyball Nes game to play

[retiredcaps]

Re: Planar PL1700-BK - backlights go out

OK,
checked the backlights and if you look at my first pic the connectors on the far left and far right don't show any light, but the middle 2 give "2 secs to black" so I guessing I need to order some cclf's. But I can check that chip if needed.

Before ordering anything, give us a few hours to digest the results and study the OZ960 datasheet.

Additionally, you may not need new ccfls. It could be the ccfl wiring that is at fault.

[De3rcr]

Re: Planar PL1700-BK - backlights go out

Before ordering anything, give us a few hours to digest the results and study the OZ960 datasheet.

Additionally, you may not need new ccfls. It could be the ccfl wiring that is at fault.

I looked at that datasheet, I can't even fit that in my mouth let onlone digest it. I was just looking for ccfl's, but it's a topploy panel they look hard to find.

[retiredcaps]

Re: Planar PL1700-BK - backlights go out

OK,
checked the backlights and if you look at my first pic the connectors on the far left and far right don't show any light, but the middle 2 give "2 secs to black" so I guessing I need to order some cclf's.

Okay, I guess the next step is to see if it is the ccfl's or the circuitry that is driving them.

So plug the "working" middle ccfl into the far left. Then try the "working" middle ccfl into the far right.

Report the results.

[De3rcr]

Re: Planar PL1700-BK - backlights go out

Okay, I guess the next step is to see if it is the ccfl's or the circuitry that is driving them.

So plug the "working" middle ccfl into the far left. Then try the "working" middle ccfl into the far right.

Report the results.

OK,
Taking the middle lights and pluging them into the outer sockets, the left(J903) one came on really dim and then shut off and the right(J906) one didn't come on at all. I plugged the outer lights into the inner sockets and they came on bright and then shut off. So when the either light is plugged into the inner sockets(good ones I hope) they all come on bright and then shut off.

I didn't know you could switch the lights around like that(add that to my troubleshooting notebook).

[retiredcaps]

Re: Planar PL1700-BK - backlights go out

OK,
Taking the middle lights and pluging them into the outer sockets, the left one came on really dim and then shut off and the right one didn't come on at all.

Okay, just going forward and to make it easier to trace and follow, the far right is which J connector? J903, J904, J905 or J906?

[retiredcaps]

Re: Planar PL1700-BK - backlights go out

And just to confirm, all the ccfls light up (when switched around) except when plugged into the "far right" connector?

[De3rcr]

Re: Planar PL1700-BK - backlights go out

Sorry,
J906 far right
J903 far left

Yes, and J903 comes on but not as bright as J904

[retiredcaps]

Re: Planar PL1700-BK - backlights go out

Sorry,
J906 far right
J903 far left

Yes, and J903 comes on but not as bright as J904

I have to run off for about 5 hours, but try resoldering the 4 backside connectors on J906 and retest. If that doesn't work, then we will have to trace out J906 and see which component(s) is bad (on the backside).

The good news is that J905 is working so we have a known good circuit for comparison.

[alexanna]

Re: Planar PL1700-BK - backlights go out

OK,
Taking the middle lights and pluging them into the outer sockets, the left(J903) one came on really dim and then shut off and the right(J906) one didn't come on at all. I plugged the outer lights into the inner sockets and they came on bright and then shut off. So when the either light is plugged into the inner sockets(good ones I hope) they all come on bright and then shut off.

I didn't know you could switch the lights around like that(add that to my troubleshooting notebook).

If you plug in the 3 other ccfls one at a time to the connector J906 that does not light the ccfl,
Do you still get no light, or do any of the other bulbs light up dimly?
Al.

[De3rcr]

Re: Planar PL1700-BK - backlights go out

If you plug in the 3 other ccfls one at a time to the connector J906 that does not light the ccfl,
Do you still get no light, or do any of the other bulbs light up dimly?
Al.

no , the lights do not come on in J906, they light dim and then go out in J903

I also resoldered J906 and J903 same results

[smason]

Re: Planar PL1700-BK - backlights go out

Here I just finished shoveling snow and it is piled about 2 feet on one side. Anyone still playing Beach Volleyball on Daytona Beach?

You must be near me. I'm SO tired of shovelling already, and it's only November....

[PlainBill]

Re: Planar PL1700-BK - backlights go out

This inverter transformer uses a newer design. Early designs had one CCFL per transformer. One end of the secondary fed the CCFL, usually through a capacitor. The other end of the secondary was either tied to ground or to a current sensing circuit. Later designs coupled the output to two CCFLs by using two capacitors.

This design uses two CCFLs driven from opposite ends of the secondary windings. The return lines from the CCFLs either go to current sensing circuitry or to ground. There are usually a few capacitors to sense voltage, and to tune the circuit.

The best way I can illustrate the difference is the old way was like two flashlight batteries, each with a flashlight bulb connected to the top and bottom. In that design, each battery and bulb set is independent of the other.

The analogy for the newer design would be two batteries in series, and two light bulbs in series. and the light bulbs connected from the bottom of one battery to the top of the other. In this case, they are dependent on the other.

This means that disconnecting one bulb of the pair is not a valid test UNLESS some provision is made to pass current through the open socket. The best way would be to use a resistor. Radio Shack 271-1131 is a 5-pack of 100K ohm .5 watt resistors. They should work FOR A SHORT PERIOD, and are normally stocked in the stores.

This is going to be crude, but what I would suggest is soldering one resistor across each unused socket (I've circled the pins of each socket in matching colors.), then plugging a CCFL into one socket, turning on the monitor briefly and evaluating how bright the CCFL lights. For the first test, I would suggest trying all four CCFLs in turn in the same socket. For the second test, I would suggest testing one CCFL at a time in each socket, with the other sockets jumpered by a resistor. Yes, this will require unsoldering and resoldering resistors. Be careful, the resistors may get hot.

PlainBill

[De3rcr]

Re: Planar PL1700-BK - backlights go out

This means that disconnecting one bulb of the pair is not a valid test UNLESS some provision is made to pass current through the open socket. The best way would be to use a resistor. Radio Shack 271-1131 is a 5-pack of 100K ohm .5 watt resistors. They should work FOR A SHORT PERIOD, and are normally stocked in the stores.

This is going to be crude, but what I would suggest is soldering one resistor across each unused socket (I've circled the pins of each socket in matching colors.), then plugging a CCFL into one socket, turning on the monitor briefly and evaluating how bright the CCFL lights. For the first test, I would suggest trying all four CCFLs in turn in the same socket. For the second test, I would suggest testing one CCFL at a time in each socket, with the other sockets jumpered by a resistor. Yes, this will require unsoldering and resoldering resistors. Be careful, the resistors may get hot.

PlainBill

I got the resistors, you say a "short period" would that be about 30 seconds or less. I just want to make sure I don't fry this board.

[PlainBill]

Re: Planar PL1700-BK - backlights go out

I got the resistors, you say a "short period" would that be about 30 seconds or less. I just want to make sure I don't fry this board.

I'd say 5 seconds or less. You want to be able to say 'Bright', 'Dim', or 'none'. You still might get 'two seconds to black', the resistances are a little low (120K ohm would be better).

I'd say little chance of blowing the board. The Radio Shack resistors are underrated for this, they will get warm.

What I'm hoping is you will find one of the two sides will be noticeably dimmer for all CCFLs (bad transformer), OR one CCFL will be noticeably different (bad CCFL or wiring).

PlainBill

[De3rcr]

Re: Planar PL1700-BK - backlights go out

I'd say 5 seconds or less. You want to be able to say 'Bright', 'Dim', or 'none'. You still might get 'two seconds to black', the resistances are a little low (120K ohm would be better).

I'd say little chance of blowing the board. The Radio Shack resistors are underrated for this, they will get warm.

What I'm hoping is you will find one of the two sides will be noticeably dimmer for all CCFLs (bad transformer), OR one CCFL will be noticeably different (bad CCFL or wiring).

PlainBill

Well, I put resistors across J903, J904 and j905 and tested J906 with the ccfl that was originally in J905 and it was dim, I left it on a little too long(15-20 secs) and smoked the resistor on J905, going to replace that and try again.

[retiredcaps]

Re: Planar PL1700-BK - backlights go out

Unfortunately I don't have any spare parts to check the ccfl's.

I don't know why it didn't click before, but the LG Flatron 1718S-BN that you repaired can be used as "good" ccfl.

You don't take out the ccfls in the LG. Just drag the LG LCD close enough to the Planar and stretch out the connector (don't let the two LCDs touch).

[De3rcr]

Re: Planar PL1700-BK - backlights go out

I'd say 5 seconds or less. You want to be able to say 'Bright', 'Dim', or 'none'. You still might get 'two seconds to black', the resistances are a little low (120K ohm would be better).

I'd say little chance of blowing the board. The Radio Shack resistors are underrated for this, they will get warm.

What I'm hoping is you will find one of the two sides will be noticeably dimmer for all CCFLs (bad transformer), OR one CCFL will be noticeably different (bad CCFL or wiring).

PlainBill

got through checking J906 and J903 and all 4 ccfl's were dim.

Then I saw this(I didn't think about this either DUH!!)

I don't know why it didn't click before, but the LG Flatron 1718S-BN that you repaired can be used as "good" ccfl.

You don't take out the ccfls in the LG. Just drag the LG LCD close enough to the Planar and stretch out the connector (don't let the two LCDs touch).

and took apart the LG and hooked it up and the ccfl's shut off after about 5 secs. Transformer???

[retiredcaps]

Re: Planar PL1700-BK - backlights go out

and took apart the LG and hooked it up and the ccfl's shut off after about 5 secs. Transformer???

Transformer appears to be okay with the 581 ohms reading.

[alexanna]

Re: Planar PL1700-BK - backlights go out

got through checking J906 and J903 and all 4 ccfl's were dim.

Then I saw this(I didn't think about this either DUH!!)


and took apart the LG and hooked it up and the ccfl's shut off after about 5 secs. Transformer???

If you haven't already try re soldering the inverter coil and anything else that's thru hole around J906
Al.