SGI GDM-5011P CRT Monitor (Sony Trinitron) Help

[nick3092]

Ok. Do you have any suggestions what to probe with the scope next? This level of troubleshooting is way above me. And I've never done anything with video signals before. So I really appreciate all the guidance so far. Which means I'll need some explicit directions on what/where to check next.

[R_J]

Are you able to access the D board? I would look at the signal on Q501/503 emitter and also the Vshape signal on ic703 pin5

[nick3092]

I am able to get to IC703 and Q501/503 by using a piece of 22ga wire to extend my probe into the vent holes. I did have the wire pinched between my fingers when I took these, but I don't think it affected the reading at all. If they look funny, I can try to take them again without holding the wire to navigate through the vent holes.

I took the IC703 print at 5ms like the others. But at 5ms Q501/503 just looked like solid line. So I backed down to 5us, and you get several square waves. Not sure how these look, as I have no idea how they should look. I did notice Q501/503 have a slight ripple or something at the bottom of the wave. I'm assuming its supposed to be flat there? Or is that normal?

IC703 - pin 5
IC703 - pin 5.png


Q501 - E
Q501 - E.png

[R_J]

I just ran across your post on another forum and there you provided different information regarding the power supply and the 200v, So do you have 200v or is it 283v? also you mentioned ic630 having wrong voltages, is that correct?

[nick3092]

The post on the arcade forums? Those values were from me trying to bench test the power supply board only. It seems when the bard is out of the chassis, the 200v rail runs high.

I get that linear power supplies run high with no load, so that can happen. But I thought this was SMPS and voltages would be spot on. When I put it in the chassis though, the voltages are all reasonable. So I gave up on trying to bench test the power supply after the post on the other forum.

Here is what I posted earlier in this thread in regards to the rails on the power supply while in the chassis that I measured this week:

-15v rail (measured -14.5v)
+15 rail (measured 14.5v)
+80 rail (measured 78.2v)
+200 rail (measured 199.3v)

[R_J]

Ok those voltages are good, I was looking for a picture I saw of another GDM-5011p monitor with the same fault https://www.ebay.com/c/13014969428, It looks like it might be a common fault.

[nick3092]

I was wondering if there might be a common fault in these monitors. When mine first started acting up, I had searched trying to find a solution. I never found anything, other than someone posted over on the CRT Gaming section of Reddit: "I bought this guy so I'd have something to play games on until I can either repair my SGI GDM-5011P's deflection board..." Which made me wonder if all these had some kind of defect on the deflection board. Maybe a bad batch of some part they used? Of course the million dollar question is, whats the defect? I'm not a member on Reddit, but maybe I'll join and see if I can message the poster to see if they had the same fault, and if they ever found the fix.

So how did the last scope images look that I posted? Any thoughts on where to probe/look next?

[petehall347]

in case you haven't seen this service manual .
https://pdfhall.com/gdm-5011p_5b6b2e...f418b45f2.html

[nick3092]

Thanks, I did find a link to the service manual that I posted back at the beginning of the thread. I did also download the service manual for that eBay monitor found by R_J. The deflection board is almost identical from taking a high level look at it.

I did a copy and paste of just the capacitor list for each into Excel and compared them. My monitor has 3 caps the other one doesn't. But otherwise all the references, descriptions, and values matched up. The part numbers differed in probably half the cases, but they were the same values.

So it's probably safe to say there is some kind of universal defect/defective part between them.

[nick3092]

Since I haven't got any more suggestions on what to look at, I went ahead with recapping the power supply board since I had the caps on hand. I was able to twist the negative terminal on the large filter (C611 330uF/450v) so that it fit the PCB. I didn't expect it to actually fix anything, and it didn't. I bought the wrong physical size caps for the 15 and -15v rail filters (C675, C677 2200uF/25v), so I left those as is. I don't think that's the issue anyway, the scope didn't show those rails looking that bad.

But it at least rules it out the power board caps. I'm hoping someone has some more ideas or things I can look at with the scope to try and figure out what the issue is.

Thanks!

[nick3092]

Not sure if anyone is still following this, but I have a (non) update. Since I don't really know what to check next, I went ahead with the only thing I know how - recapping the A board (RGB/video amp). Unfortunately, seems to have made no difference what so ever. The only board left I haven't replaced the electrolytics on is the L board (V stat, H stat, LLC, Geo magnetic sensor). I highly doubt the issue is there. But I had to order some other parts, so I did order those caps as well. I don't have anything to lose by recapping them at this point.

Otherwise I would really appreciate any more guidance on this if anyone has any ideas.

[nick3092]

Wrapping this thread up. The culprit turned out to be IC007, the defection processor. Apparently Sony used this same design (N3 chassis) in several of its own and re-branded monitors, and it was quite common for this IC to fail in that chassis and cause these symptoms. I found an NOS one for a reasonable price and found someone local who does SMD rework for a reasonable price as well.

Monitor is now happy, and so am I. Thanks to everyone for their input.