Advice sought re; faulty 21" Dell D1626HT CRT (Trinitron)

[Panda]

Hi all,

I have a very nice (condition wise) Dell D1626HT which I bought from someone who had found it in their loft.

I have been using it on and off for the past couple of weeks.

When I first started using it, it would click and "flicker" the screen occasionally, but this reduced in frequency over time until it was only a very occasional thing.

Unfortunately now it seems like it is now not registering inputs correctly. I think it is going to "no signal" when it sees an image above a certain resolution.

At first it would display the desktop just fine, but then it would cut out and go to the "no input" screen with the same relay click you hear when the resolution changes. If I power cycled the monitor, the picture would come back, but then it would go again after maybe 10 seconds.

Currently when I power it on it displays the POST screen, then goes to no input, then comes back at the OS loading screen, then goes back to no input again. So it seems like it is relatively happy displaying those low resolution images. I can now no longer get it to display my desktop, which is only set to 1280x1024, bearing in mind this monitor is theoretically capable of displaying 2048x1536.

I bought a VGA to BNC cable to see if it behaves any differently when connected via the BNC connectors, and it does, it sometimes shows the "no input" screen, but most of the time it just displays a completely blank screen, as though it sees a signal but cannot display it.

I have tried plugging different devices into it, as well as different GPUs in the PC it is usually connected to, with no success.

Here is a video of what it is doing on a VGA signal: (please ignore the issue with the colours, that is because of the VGA cable, I was trying a different one which happens to need a clean)

I am fairly confident in opening it up and taking a look inside, my main concern is honestly being careful not to damage the plastics in doing so.

From what I can see through the grilles with a torch, it is fairly grubby inside, so the first thing I am going to do is give everything a clean, and then inspect it for physically damaged components or obvious solder cracking.

I would greatly appreciate any input from folks more knowledgeable about such things, in letting me know what else to try or to check.

I have a multimeter but I don't have an oscilloscope or any specialist test equipment.

Lastly on the slim chance someone reading this is local and would be willing to take a look at it in person, I am in the UK, near Norwich.

Many thanks in advance!

 

[andy]

Start with the basics. Blow out the dust, and inspect the boards for obvious problems like bad soldering, leaking capacitors, or cracks in the board. An ESR meter would be a good investment since some capacitors may have dried out if the loft was hot.

The click and flicker problem may be cause by high voltage leakage around the CRT's anode connector. It's not a bad idea to remove it, and thoroughly clean the CRT, and the rubber cup. When reconnecting it, I like to smear a little silicone grease on the inside of the rubber cup to help form a tight seal.

 

[Panda]

Start with the basics. Blow out the dust, and inspect the boards for obvious problems like bad soldering, leaking capacitors, or cracks in the board. An ESR meter would be a good investment since some capacitors may have dried out if the loft was hot.

The click and flicker problem may be cause by high voltage leakage around the CRT's anode connector. It's not a bad idea to remove it, and thoroughly clean the CRT, and the rubber cup. When reconnecting it, I like to smear a little silicone grease on the inside of the rubber cup to help form a tight seal.

Thanks Andy, I will do!

Will post pictures and thoughts once I've opened it up.

I am a bit worried that the problem may be some kind of deflection IC which I see people who have issues with this family of Trinitron monitors mentioning as being problematic, but I'd have thought it wouldn't display anything, or there would be obvious picture distortion, rather than it behaving this way?

I took a couple of better videos in the mean time, with less messing about with the power button and a cleaner video signal, so it's clearer what's going on.

Firstly here, already powered on, and then I power on the computer. You can see it flicks into life to show the BIOS splash screen and the POST messages, and then flicks off, then back on for OS loading, then off again after a while sitting on a blank screen.

And here it is with no input (cable connected, PC off) being powered on. In a darkened room I noticed curious flashing at the edges of the tube before it woke up.

I can also press and hold the menu select button which makes it display a gray-white screen with banding, and makes the power light flash orange and green. I don't know what this means if anything, it's just something I found I could do!

And pressing the contrast+ button displays coloured bars as it should, but there is a flashing line a across the top of the tube which I'm sure shouldn't be there.

When I turn if off I can also hear faint electrical ticking from inside the chassis somewhere...

 

[Panda]

I got her opened up.

I think its seen a reasonable amount of use in its life, there was a layer of black dust clinging to the back of the tube, and everything inside has a fair amount of dust on it, the kind which clings and doesn't blow off. The anode cap was secure and flush and had a nice layer of grease under it. There are signs someone may have been inside it before, messy use of white adhesive goo, and a couple of marks where a tool has slipped near a screw hole, but it may well have been that way from the factory. The soldering is some of the nicest and most intricate I've seen inside any old electronic device, its a nicely put together thing!



I took the neck board and each of the side boards out and inspected them and the only thing I found that was definitely visually dead was the electrolytic in position C905:



I also found that the ground wire that is supposed to go somewhere on the input panel (probably on the back of the VGA cable standoff, which was missing) was hanging loose. It was probably making some contact some of the time just from its own weight, but thats it... Unsure how critical that ground is likely to be!



An album of other pictures I took while inside, there are a couple of resistors with some corrosion on them, one enough so that it has flaked off some of the ceramic coating, and the board which lives in the base of the chassis is quite dirty, but otherwise everything visually looks good to me, aside from that one electrolytic...

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And here is a copy of the Sony GDM-500PS service manual / schematics for anyone who might be looking for it. There may be minor differences, but I understand the 1600HS series is practically the same internally.

sony-gdm-500ps.pdf

drive.google.com

 

[Panda]

I found and uploaded the proper manual:

dell_d1626ht_n3_sch.pdf

drive.google.com

 

[Panda]

I took the D board out completely, and in doing so discovered that the video signal connector was badly corroded, and the ground pin actually snapped and came away with the connector when I unplugged it.



So now that connector is also being replaced, as well as all the other components on the board checked.

I looked at how close everything was packed together in these areas and decided not to try and tackle it myself. I'm taking it to a friend to do for me.

 

[andy]

At least you've found some obvious problems to start with. That leaking cap is in the high voltage regulator circuit, so it could be causing most of your trouble.

Based on how the monitor looks inside, I would check all of the small to medium size caps for ESR in circuit, and replace any that test questionable. I'd also check every board over for bad soldering. Don't forget about the power supply.

 

[Panda]

Thanks. There's a pic of the power supply board in the other photos linked in my post, it looked good. Better than everything else in-fact. (Maybe thats what got replaced when someone was in here in the past?)

I've asked my friend to test all the caps on the D-board and replace any that are iffy.

Perhaps it would be worth also taking him the other boards to test...

 

[HaHa I]

Perhaps it would be worth also taking him the other boards to test...

Always check everything when you have something apart, better safe then sorry and have to fix more down the road.

 

[Panda]

Always check everything when you have something apart, better safe then sorry and have to fix more down the road.

Yeah, it definitely makes sense.

He is a very talented individual whose time is valuable, and I am poor, that's the only problem.

I was hoping to do these repairs myself, but everything is so tightly packed, its not like replacing a capacitor on an average motherboard.

We'll see what he says.

 

[HaHa I]

I was hoping to do these repairs myself, but everything is so tightly packed, its not like replacing a capacitor on an average motherboard.

If you can replace caps on a motherboard I'm sure you can replace caps on the boards in this CRT, just take a little more time and maybe get a thinner tip for your iron. If you feel over whelmed or start screwing up take a step back and come back to it later.

I took a quick glance at the photo album and other then a lot of dust/grime, some cracked ceramic and crappy old caps I don't see anything that stands out other then at ground and the one cap. My money is something on the input site of the CRT and not with the neck. driver, fly back or power board. But I have seen something like with with a bad power switch, when you hear the click does the power LED change at all?

If this was my CRT and I was fixing it I would replace the smaller caps near that one that was leaking, clean it all out, contact cleaner on all the connectors including the neck board and fix the ground wire you brought up. then see if that fixes it. I see a screw right next to that ground, you might be able to put it there.

EDIT: I might have missed this but did you try hooking up the CRT to a different PC or video card?

 

[andy]

All of the video processing happens on the CRT neck board. It's enclosed in metal shielding, and can run somewhat hot, so worth checking at least the smaller caps, which are much more likely to dry out that the big ones.

The power supply uses a single sided board which is more prone to developing cracked solder connections than the other boards, which are plated through hole. It also generates a fair amount of heat, so worth checking the caps.

If you've replaced caps on a motherboard, then this will actually be easier. Motherboards have thick ground planes with a lot of thermal mass that makes soldering difficult. The boards in your monitor, while crowded, won't be nearly as hard to work on. Disassembling, and reassembling the monitor are the hardest parts of the job, so check everything you can while you have access.

 

[HaHa I]

If you've replaced caps on a motherboard, then this will actually be easier. Motherboards have thick ground planes with a lot of thermal mass that makes soldering difficult. The boards in your monitor, while crowded, won't be nearly as hard to work on.

wile this is very true there are things to make the boards in the CRT like this harder to work with too, the traces and vias on such boards tend to be more fragile then on a motherboard and less forgiving if your iron is to hot, the tight space/packed together layout can be hard for some with poorer eye sight or less stable hands and mentally daunting for those not used to working on them. I think its a pick your poison kind of thing as they both present their own kind of challenges.

 

[snowman]

Just some feedback on the click and wavy picture (for a moment) when you first power it up. Imo this is normal and would be the degaussing coil clicking on to degauss the screen at powerup. Most vga monitors from the 90s on up had degaussing coils. They are necessary .