Westinghouse L1928NV

[keiser]

19 inch monitor began to flicker slightly. Annoying.
I replaced 4 CapXon capacitors that were buldging with Rubycons.
Still had the slight flicker. No hissing.

I wiggled the Chi Mei branded screen apart.
One lead of the CCFL immediately fell off.
I assume this was the problem. Bulb not blackened so I made a splint for
the short stub on the CCFL and resoldered the lead.

Reassembeled but no joy.
Unit fires up, the inverter hisses and goes to protected mode in a few seconds.

Testing individually, the bulbs light for a few seconds as well. No hiss from inverter with single bulb.
So I think bulb is now good.

I'm guessing load is imbalanced.

The leads emerge through a small opening in the metal casing. I wrapped in
tape but the fit is tight. Maybe excessive leakage?
Should I just redo this and hope for a better result?
Suggestions?

Thanks.

[Lumberjack777]

Re: Westinghouse L1928NV

Should I just redo this and hope for a better result?
Suggestions?

Thanks.

Yes, I'd redo it. The high voltage from the inverter is always looking for a place in the wiring to short and arc. That's a very common problem. What you can do is attach the bulbs after you have it apart again. Then fire it up and see what happens. Might need to resolder that wire, or another wire. At least by testing with the bulbs out, you'll have a better idea of the problem.

[keiser]

Re: Westinghouse L1928NV

A snap to disassemble now. But separating the leads made no difference.
About all I could observe is that 1 tube is ever so slightly dimmer than the other 3. Swapping leads did not change which tube was dimmer.
[The dimmer tube is not the one that had the broken lead.]
The connections "sounded" good [no hiss at the joint] but since they are buried in a block of rubber, to go further would be destructive.
The "hum" comes from [one of] the inverter transformer[s].
Might that be enough imbalance to set off protected mode?
I read a hunt that there is a way to defeat protected mode. Anyone care to share so I can test further?
Thank you,

[budm]

Re: Westinghouse L1928NV

You can try Swapping the transformer location, also compare the resistance reading on the high voltage winding side of both transformers.

[Lumberjack777]

Re: Westinghouse L1928NV

A snap to disassemble now. But separating the leads made no difference.
About all I could observe is that 1 tube is ever so slightly dimmer than the other 3. Swapping leads did not change which tube was dimmer.
[The dimmer tube is not the one that had the broken lead.]
The connections "sounded" good [no hiss at the joint] but since they are buried in a block of rubber, to go further would be destructive.
The "hum" comes from [one of] the inverter transformer[s].
Might that be enough imbalance to set off protected mode?
I read a hunt that there is a way to defeat protected mode. Anyone care to share so I can test further?
Thank you,

You can test the secondaries of the inverter transformers with a digital multimeter. http://preher-tech.com/documents/tes...ormersinlcdtvs
Around here, most people say that a difference of 3% or more in ohms indicates a bad inverter transformer.
I'm a little confused because it only started humming after you "fixed" the wiring of that one bulb. Is the inverter humming from the side with the dimmer bulb? If so, that's probably it. Especially if the inverter transformers passed the test. The ccfl's are normally very bright.

**Edit** Thanks budm. You always did type faster than me

[keiser]

Re: Westinghouse L1928NV

While there was annoying occasional flicker I heard no hissing.
And never went into protected mode.
That all started after I resoldered the bulb.

I have a DMM and an ESR. I will recheck next week when I have some free time.

The dim bulb remain dims when I swap connectors so I am thinking that rules out one of the inverter transformers. The dim bulb is NOT the one I resoldered. I suppose I should dissect that connection next.

Thnak you for your comments. I will report back soon.

[budm]

Re: Westinghouse L1928NV

The dimming or half-way lit is the indication of the lamp not getting full voltage to the lamp so it can be bad connection at the socket (bent pin) on the board or the connector of the lamp wire, poor solder connection at the lamp ends, bad high voltage winding, bad ballast cap, or what ever that can cause the lamp not to get the full voltage to the lamp.