Silicon Graphics 20D11 monitor help

[darkhelmet02]

Hi all. Hoping someone here can guide me through repairing an SGI 20D11 CRT monitor I acquired recently. Currently the monitor turns on and displays a very very dim gray screen (not a line or dot) after a few minutes. This does not change when the monitor receives a valid video signal. Changing the brightness/contrast settings with the remote does not change the gray screen, however I can verify that the remote is working as I can degauss the monitor and move the image around. I've inspected the boards for cracks in the solder joints and I have not found anything obvious. Is recapping the next step? I don't see any leaking electrolyte anywhere, but I also don't want to take the shotgun approach and replace every single capacitor in the monitor if I don't have to. I have very very basic skills in troubleshooting electronics, but I possess the appropriate tools to do so. Is there something else I can check to troubleshoot this further? Thanks!

EDIT: Made the post a bit clearer.

[wasedadoc]

Have you any experience repairing CRT monitors?

[inse]

Very difficult to give any hints with this vague description.
A) do you feed a valid video signal?
B) grey screen means entire screen is lit up, not a dot or line?
C) anything to observe of the picture applied (if so)?
D) does the monitor have OSD or analog control of brightness, contrast etc?
E) you acquired it already broken?
F) any experience in electronics repair??
G) do you have schematic or service manual?

To begin with

[aeg]

Model number? What signal source?

[darkhelmet02]

I do give it a valid video signal through the 13W3 input. Using a good cable, with a machine I know works on another SGI monitor. The grey screen means the entire screen is lit up, it is not focused in one area. With an SGI connected to the monitor there is no change in the grey screen. This monitor does not have an OSD, but it does have a remote to change brightness and contrast. Changing the brightness and contrast settings makes no difference. I did acquire this monitor already broken. I do have extremely basic experience with electronics repair. I have mostly recapped broken power supplies successfully, and I have worked on another Sony CRT monitor before. I have not been able to find any schematics/service manuals online. The monitor is a rebranded Sony GDM-20D11

[inse]

Did you look here whether one of them fits sufficiently?
https://elektrotanya.com searching for Sony GDM-20
At first I thought one of the grid voltages on the tube might be missing but as there is no reaction to the signal, the problem probably is in the signal path.
I would start from the CRT neck PCB with the supply of the video amplifier.
Hardly possible without schematic. Be careful about the HV present in the set!
Probably there is going to be a lot of metal shielding, have fun!

[aeg]

I'm amazed that any of these are still out there. They were great monitors but the DA board is a ticking time bomb and I figured most of them would have been scrapped when they stopped working.

Sony never made the GDM-20D11 service manual available to the public. The GDM-20SHT is the closest model with readily available service literature.

The first thing to do is replace all the surface mount capacitors on the DA board. Twist them off with pliers then desolder what's left of the leads.

If your DA board is A-1341-684-D then you need 27pcs capacitors:

1uF/50V ⌀4mm 9pcs
2.2uF/50V ⌀4mm 2pcs
4.7uF/35V ⌀4mm 1pcs
10uF/16V ⌀4mm 1pcs
10uF/35V ⌀5mm 2pcs
22uF/16V ⌀5mm 6pcs
47uF/16V ⌀6.3mm 6pcs

The earlier A-1341-684-C board may have one fewer 2.2uF/16V capacitor.

While you're in there, you should ESR test all the capacitors on the D board and replace the bad ones.

If after this you get good video but it's still dim and slow to show a picture, I would check if the heater voltage is less than 6.3VDC (be careful, there is high voltage on other CRT neck pins) and if so, check C661 and C664 on the G board next to the 4-terminal TO-220 regulator IC655, and check the IC655 soldering and traces for hairline cracks. I don't think I've seen this problem on this monitor, but it happens on the other 20" models.

[aeg]

Side note, inse is right to also suspect something in the video signal path (A board). The DA board usually affects deflection, but I'd still re-cap it first thing before it goes nuts and blows a semiconductor. Also, the D board controls sub drive to the cathode pre-driver so it could still be responsible for loss of the video signal.

[inse]

Hey there is an expert on this model :~)
I have no experience with this specific monitor, I just tried to give general hints.

[darkhelmet02]

Thank you so much for the suggestions inse and aeg! This is fantastic information. I will take the monitor apart tonight and check out my DA board. I seriously appreciate it

[inse]

How‘s the repair going?