[sorin_paul]

Hello,

The CRT on one of my Okuma LB15 OSP5000L-G has become black. First, the RED color disappeared, then GREEN, and after a few hours, the CRT was black. The lathe is working, moving, all is OK except the CRT.
At first, I presumed that the CRT is dead, and I have tried to replace it with a LCD and a CGA to VGA converter(done it before on another LB15), but same result. There is H, V sync signal, but nothing on RGB (checked with oscilloscope ).
Any clues where to find the problem?

Thanks

[fordav11]

replace (or repair) the video output board in the main board stack in the rear cabinet.

[sorin_paul]

It is possible to swap the old CRP card with a newer model CRP card?
The old one is a double PCB card CRPB-II E4809-436-018-C serial nr 1911-164 1-1187
The newer is a single PCB card CRP II-C E4809-045-106-E serial nr 1911-1692-40-185
Here are some photos:
Attachment 262306
Attachment 262308
Attachment 262310

[fordav11]

yes the newer card should be compatible. the new card uses some different components to reduce size and cost

[sorin_paul]

I have replaced it, but no difference. The lathe works, but still no RGB.
Is there a possibility that the video signal is processed somewhere on the CRT panel? Some buffer circuits or something. On R, G, B, signals on the flat cable that goes to the monitor I have about 2.5V, equal and flat on all three signals.

[fordav11]

there are some electronics in the panel but they are mostly for the panel itself.
as far as I know the wires for RGB come directly from the video board to the monitor. but you will need to check your machine since they can be different. there might be a video amplifier there. or some times custom video DAC (wide black ceramic package standing vertically on PCB) or logic like 74LS07 (commonly used to drive R,G,B signal at final output stage)
in my panel box there is a power supply..... this provides 110V for the monitor and 5V for logic boards in panel box. so check that also. the neck on the back of the tube should be glowing orange signifying that high voltage is there.
also check the RGB output signals directly on the video board. if they are the same level voltage then the problem is still in the PCB cage at the rear of the machine.
next thing to change is any other graphics-related board. I do not know the 5000 so I cant tell you what exactly and Okuma manuals do not have that info like Fanuc Hardware Description manual has.
If you take some photos of the PCBs (and better quality than above) I could make some suggestions. if still a PCB, certainly it has to be video related PCB, not CPU related.
you can check the video board yourself. it will need to be inserted and powered when testing. find video chip (possibly HD6845 or similar). connect micro-clips to the pins for hsync, vsync, 1 pin of address bus/data bus, clock etc, plug in PCB and power on and check other end of micro-clip wire with logic probe or oscilloscope. if hsync/vsync/clock is present and you see movement on address/data bus pins there is video data there. meaning your new video board is still faulty on output stage. if no data then input data is missing. possibly coming from CPU board or some other board that processes the video signal.
if you want to do more detailed diagnosis and provide high quality pics PM me and we can talk at length in emails

[fordav11]

if your monitor box looks like the pic below then there are some boards there on the left that could be bad. check the one where the video cable plugs in first.

[sorin_paul]

Thank you,
I found that RGB signals are sent to this boards inside the CRT panel, not as TTL signals, but differential signals (noise removing). Those signals are OK, but haven't found the time to check the boards with an external power supply (not possible inside the CRT) . There are 4 IC's involved, 2pcs SN75108AN - line receivers, and 2pcs M53237P (74SN37).

[giovannilannino1977]

hello, could you specify where i can find the video card? do you have any photos to show me to identify it? would you have a video card to sell?

[giovannilannino1977]

I also think I have the same problem described above