DELL P1110 Trinitron - focus problems

[manoleo]

Hello, I am having problems with my Dell P1110 21" Trinitron monitor. It changes it's focus on it's own. One moment it's very blurry and the next it's ok. Sometimes it's ok only in the center of the screen, sometimes only in the corners. It's very random.

Adjusting the focus from the knobs on the FBT is not possible. I have also tried the monitor with an FBT and an A board from a working Sony FW900 but it's the same, so I'm guessing it's not the FBT or the A board.

I read somewhere that this monitor should have an auto focusing circuit controlled by an IC. I am bad at reading schematics so can anyone please help me find this auto focusing circuit and the IC?

I am attaching the service manual in case someone wants to check the schematics.

Thanks in advance!

[manoleo]

Re: DELL P1110 Trinitron - focus problems

I have tried to capture the problem on video but it's very hard. However on this video you should be able to see how at 0:05 the focus snaps back to normal. It happens on it's own without me touching anything. After this happens the image slowly gets blurry again until it snaps back to normal at a random moment. This goes on and on.

Any kind of advice would be greatly appreciated.

[dick_barton]

Re: DELL P1110 Trinitron - focus problems

I have tried to capture the problem on video but it's very hard. However on this video you should be able to see how at 0:05 the focus snaps back to normal. It happens on it's own without me touching anything. After this happens the image slowly gets blurry again until it snaps back to normal at a random moment. This goes on and on.

Any kind of advice would be greatly appreciated.

There is no video showing on the link given

[R_J]

Re: DELL P1110 Trinitron - focus problems

If you tried a different FBT then it is likely the crt that is at fault, the focus element in the crt is going open. There is no auto focus, there is dynamic focus correction for the edge. this is controlled by the DFT transformer (H) and by Q707 (V). If the dynamic focus was the problem it would effect the edge and either the top/bottom or sides but not likely both.
You can check the crt socket on the C Block where the focus leads are connected.
If the focus controls have no effect it is likely that the crt is the problem.