Dell P1110 21" CRT repair thread

[Th3_uN1Qu3]

Re: Dell P1110 21" CRT repair thread

Start by checking the mains fuse. If the fuse is blown, check the main switching transistor, it probably failed shorted. It doesn't go on its own - so check the capacitors too, one or more could be bad.

If the fuse isn't blown and the transistor looks fine check the controller IC in the power supply. Btw, if the main supply runs but seems to be in protection mode (listen for a ticking noise), check the HOT (horizontal output transistor). That is by far the most common part to fail in CRT monitors.

The service manual is pretty easy to locate and the schematics are very detailed so troubleshooting should be straightforward. If you can't find it i'll upload it here. Edit: This is it: http://www.eserviceinfo.com/download..._CPD-E500.html

[deathamatend]

Re: Dell P1110 21" CRT repair thread

Thank you so much for replying. I do very well with soldering so I can pretty much handle it all. I did one of those 19" Westinghouse monitor power supply re-caps successfully. P1130 is just huge and many components. Inside is spotless and everthing is readable. Just need some pointers for another successful repair. Can I upload pitures at Badcaps? It would help. Thanks

[Th3_uN1Qu3]

Re: Dell P1110 21" CRT repair thread

Course you can. Resize as close to 2000x2000 as possible, click on advanced under the quick reply form and upload using the attachments function.

[Th3_uN1Qu3]

Re: Dell P1110 21" CRT repair thread

PlainBill asked for WinDAS so here it is.

[Th3_uN1Qu3]

Re: Dell P1110 21" CRT repair thread

Haven't kept you up to speed with the news, have i? A while back i got a P1130. It only had the excessive brightness issue, after adjusting with WinDAS everything is fine. As opposed to my P1110, it didn't do the whole "start up bright then slowly drift back to normal" thing. And by slowly i mean slowly - the darn thing took over 2 hours for brightness to stabilize, and if the computer went idle and turned the monitor off, then it would do the same thing over again. The P1130 worked normally after i adjusted the G2. Interestingly, the P1130 got a G2 voltage of almost 100 volts above the P1110 for the same brightness range, and i started to dig further.

Turns out there was a little difference in the video circuitry of the P1130 (built in 2003) as opposed to the P1110 (built in 2000). Attached you will find the relevant portion of the schematic of the P1110. Take note of pin 17 of the cutoff amp, with the funky self-biasing transistor circuit. Someone had analyzed the circuit before and it turns out it was some kind of thermal compensation, but noted that it does affect brightness. Well, compensation or not, the P1130 didn't have this, and instead connected pin 17 directly to ground. It also didn't have the brightness drift issue.

So, connecting the dots, i bypassed the drift correct thingy on the P1110. The brightness got significantly lower, i had to adjust G2 value with WinDAS again. The new G2 voltage for the P1110 was almost identical to the one the P1130 wanted. And... NO MORE BRIGHTNESS DRIFT!!!! I can finally have a proper monitor. Well, in fact, now i have two proper monitors.

Now, some might wonder what was the circuit doing there in the first place. Well, i think i got an answer for that. As you know, vacuum tubes take a while to warm up, and CRTs are no exception. A CRT monitor starts up dark and takes a few minutes to warm up and get to normal brightness. What Sony wanted to do was to eliminate this warmup period, so they put that little transistor that shifts the cutoff amp's bias point during this warmup of the tube, so the brightness starts up at nominal levels from the get go.

At least that's the theory. And it probably even worked when the monitor was brand new. But apparently the bloke who put that little transistor in there forgot to factor in the aging of the tube... and thus the circuit ends up overcompensating, causing the brightness drift i mentioned above. A monitor that takes 5 minutes to brighten up is lots better than one that starts up over bright and takes two hours to get to normal. Plus given its position on the board, i cannot possibly understand how that transistor could have ever sensed the temperature of the tube, or even of the video amp for that matter... No wonder it got removed in the following version.

Anyway, there you go. If you ever see one of those, now you know how to fix it. IIRC lti had a Sony Trinitron with the same brightness drift issue, get to work already man!

[FIXITNOW]

Re: Dell P1110 21" CRT repair thread

good job

[freaker]

Re: Dell P1110 21" CRT repair thread

Anyone have a clue as to what is occurring when a P1110 immediately shuts off after a few seconds regardless of which input is used. Prior to completely not powering up, I could flip the switch from the input it was connected to over at power up and flip it back after a few seconds and it would power up.

I went through and cleaned up the inside. Old tarnished thick dust and visually checked for pad components but nothing evident. Looks almost new now except for the side effect of not power up the tube.

[momaka]

Re: Dell P1110 21" CRT repair thread

Very interesting find, Th3_uN1Qu3!
Since I have some Sony CRT monitors as well, I decided to check the schematics of their A-boards and here's what I found:
My 21" 1998-built Dell D1626HT doesn't even have a cutoff AMP IC for the RGB. Instead, it has a separate transistor/op-amp circuit for each. So I'm not sure if this incorporates such a drift correction circuit. See lower-right corner of attached picture.
On the other hand, the Sony GDM-FW900, does have this drift correction circuit. In fact, the cuttoff AMP is the same as yours. Heck, even that portion of the schematic you posted is exactly the same as the FW900's - same part numbers at the exact same locations with the exact same board numbers. I think I will grab me a copy of the P1110 schematic. I still need to find a flyback for that other GDM-FW900. I doubt the P1110 will be compatible, but I'm still curious to see how much in common they have. Last month I saw 2 of these P1110 CRT monitors on Craigslist here.

By the way, my D1626HT has good colors, but the contrast seems a little weak - that is, if I want bright whites, I have to turn up the brightness. But then the blacks become washed out. And if I turn down the brightness so I get nice deep blacks, then my whites are a bit dull. My contrast and color bias/gain are turned all the way up. Does this sound like a G2 issue? Or old tube, perhaps? I have somewhat corrected this issue by turning up the gamma through software. Colors are still not as vibrant as my older 17" Dell D1025HTX, though.

[Th3_uN1Qu3]

Re: Dell P1110 21" CRT repair thread

I went through and cleaned up the inside. Old tarnished thick dust and visually checked for pad components but nothing evident. Looks almost new now except for the side effect of not power up the tube.

Does the heater still glow when it turns off? Or does the whole monitor go into standby?

Very interesting find, Th3_uN1Qu3!
Since I have some Sony CRT monitors as well, I decided to check the schematics of their A-boards and here's what I found:
My 21" 1998-built Dell D1626HT doesn't even have a cutoff AMP IC for the RGB. Instead, it has a separate transistor/op-amp circuit for each. So I'm not sure if this incorporates such a drift correction circuit. See lower-right corner of attached picture.

Everything that should be connected to ground is connected to ground, so there is no such circuit in there.

I think I will grab me a copy of the P1110 schematic.

Here you go: http://www.eserviceinfo.com/download...ell_p1110.html

By the way, my D1626HT has good colors, but the contrast seems a little weak - that is, if I want bright whites, I have to turn up the brightness. But then the blacks become washed out. And if I turn down the brightness so I get nice deep blacks, then my whites are a bit dull. My contrast and color bias/gain are turned all the way up. Does this sound like a G2 issue? Or old tube, perhaps? I have somewhat corrected this issue by turning up the gamma through software. Colors are still not as vibrant as my older 17" Dell D1025HTX, though.

Check G2 voltage as per your service manual. Probe before the resistor that feeds it to the tube (otherwise the impedance of your multimeter will have an effect and the reading will be inaccurate).

If the picture is otherwise correct (no color issues, no trailing shadows or things like that), i'm guessing aged tube though.

Btw, i'm currently developing a method of thermal compensation involving the CRT itself - my P1110 still takes 15-20 minutes to warm up and 30 minutes to fully settle, and this is entirely due to the thermal dependence of the tube. The method i've devised should allow for <5 minutes warmup time, and uses a minimum amount of parts. It will control G2 voltage based on tube temperature, and will be done with a NTC thermistor placed on the tube neck and either a small micro (easier to set up) or just a couple trimpots (simpler, but takes a longer amount of time to tweak). I'm partial to the microcontroller solution, i have a couple PIC12F675s lying around doing nothing, and it's easier to touch up, as the percent of brightness drift over temperature will vary with the age of the tube.

[lti]

Re: Dell P1110 21" CRT repair thread

Anyway, there you go. If you ever see one of those, now you know how to fix it. IIRC lti had a Sony Trinitron with the same brightness drift issue, get to work already man!

I never figured out how to get the cover off.

[momaka]

Re: Dell P1110 21" CRT repair thread

Everything that should be connected to ground is connected to ground, so there is no such circuit in there.

Good to know. At the time I saw this monitor on Craigslist, there were some listings for a few other big monitors, most of them much newer. But I chose this one on purpose. It seems that these old non-flat Sony's are built a little better than the newer ones.

Here you go: http://www.eserviceinfo.com/download...ell_p1110.html

Thanks. I downloaded it but still haven't looked at it.

Check G2 voltage as per your service manual. Probe before the resistor that feeds it to the tube (otherwise the impedance of your multimeter will have an effect and the reading will be inaccurate).

Thanks for the suggestion. I'll probably do that after I do a bit of prep-work on my 830D multimeter (the separation between the input terminals seems a bit close, so I think it would be wise to add some insulation first if I decide to measure such high voltages).

If the picture is otherwise correct (no color issues, no trailing shadows or things like that), i'm guessing aged tube though.

None as far as I can tell. Like I said, the color is good, but just not as good as some of my other CRT monitors. What particularly bothers me is the brightness - I can turn it up, but only the dark colors become brighter. The whites stay almost the same (but IMO they should be a little brighter). Other than that, I really like it.

I never figured out how to get the cover off.

You're kidding, right? CRT monitors are a piece of cake. Moreover, none of them require prying like LCD monitors.

[freaker]

Re: Dell P1110 21" CRT repair thread

Does the heater still glow when it turns off? Or does the whole monitor go into standby?

I do not see anything glowing with the cover off.

With nothing connected and powered on, the green light comes on solid for a minute or two. Then it switches to a solid but dim orange.

If either port is connected and the switch is not set to that port I get the same result. However if I switch to that port it will sound like it powers up the tube. The lights goes green then immediately, 1 sec, turns orange and blinks every 2 seconds. Off for 2 seconds and on for less than a second. {edit: According to spec it would appear to be ABL protector}

[Th3_uN1Qu3]

Re: Dell P1110 21" CRT repair thread

ABL protection tripping means high voltage is too high. Usually a sign of a bad flyback.

[freaker]

Re: Dell P1110 21" CRT repair thread

ABL protection tripping means high voltage is too high. Usually a sign of a bad flyback.

Thanks, I'll see what I can google up. Sounds like it is beyond my electrical abilities. But who knows, maybe I can find a fix like I did here at badcaps for an old broken LCD controller.

[momaka]

Re: Dell P1110 21" CRT repair thread

If either port is connected and the switch is not set to that port I get the same result. However if I switch to that port it will sound like it powers up the tube. The lights goes green then immediately, 1 sec, turns orange and blinks every 2 seconds. Off for 2 seconds and on for less than a second. {edit: According to spec it would appear to be ABL protector}

Is there a screeching sound when that happens? If you look on the left side through the vents on the back of the CRT with the front of the CRT tube facing you, do you see any white-blue glow?
Reason I ask is because I looked at the schematic for the D-board, and it seems identical to what I have in my 24" GDM-FW900. I hope you don't have the same problem as I wasn't able to fix mine yet, and it's starting to look more and more like the tube has leaked air.

[lti]

Re: Dell P1110 21" CRT repair thread

You're kidding, right? CRT monitors are a piece of cake. Moreover, none of them require prying like LCD monitors.

No, I am not kidding. Look at the thread I made about it.

[freaker]

Re: Dell P1110 21" CRT repair thread

Is there a screeching sound when that happens? If you look on the left side through the vents on the back of the CRT with the front of the CRT tube facing you, do you see any white-blue glow?
Reason I ask is because I looked at the schematic for the D-board, and it seems identical to what I have in my 24" GDM-FW900. I hope you don't have the same problem as I wasn't able to fix mine yet, and it's starting to look more and more like the tube has leaked air.

Doesn't make any sound. But I know the pressure on the inside of the tube is the same as the outside. If it wasn't when it happened it is now. [edit: Ok maybe not. It was just the anode cap and not actually the vacuumed space of the tube. ]

[momaka]

Re: Dell P1110 21" CRT repair thread

No, I am not kidding. Look at the thread I made about it.

I don't see it. This one by any chance?
https://www.badcaps.net/forum/showthread.php?t=14795

Doesn't make any sound.

Nothing? No clicking or ticking either?
I'm not familiar with the P1110, but I suppose there should still be a clicking sound from the degauss coil relay when the monitor tries to start.

It's unlikely, but the power supply could be bad too. On my second GDM-FW900,the power supply would not come out of stanby *most* of the time (but occasionally it would and would work fine). I wonder if the Dell P1110 have the same issue, given how related these monitors seem to be.
To see if that's the issue, you would need a multimeter to check if the PSU gives the proper voltages when the monitor tries to start.

[Behemot]

Re: Dell P1110 21" CRT repair thread

Ohhhh, CRT lovers, I found paradise

I unfortunatelly had to brick sopme displays which died for me in the past years, amongst them was one 19'' Mitsubishi DiamondBack with totally perverse colors for its age. I will miss him Had bad caps, but was working like charm till it bricked completelly.

Anyway, now its cheap, I even got Phillips Brilliance 202P4 for free:-D Currently have this with Dell P1130 and one spare HP (but its big like house:-D).

Do you mind if I will bother you if something happenned to them? So far I only spilled juice over the Phillips once and had to change SMD switches on the front after few months (they died completelly), since than it works fine *pit-pat*

[lti]

Re: Dell P1110 21" CRT repair thread

I don't see it. This one by any chance?
https://www.badcaps.net/forum/showthread.php?t=14795

Yes, that is the thread I was talking about.