thanks all.. alignments checked, lamps, and belts have all been changed out numerous times now. The scanner has not been moved, nor the ac power been changed in any way. I don't use a UPS or any kind of regulator, but I confess I never have over the years. I'll get back into it and check connections again, and run the FST tests agin a suggested..
Intermittent problems are the worst...
latest FST results.. all passed repeatedly including PMTs, HVPs failed in green consistently.. not sure what that means... back to the manual after some fresh air...
With this new FST data my guess is either a bad High Voltage Power Supply (HVPS) for the green PMT or possibly a bad VDC (Video Digital Controller) board. This is just based on my reading of various sections of the 4500 Maintenance Manual and general understanding of electronics and the electrical design of the 4500. It is NOT based on any first-hand repair experience with the 4500.
FWIW
thanks Dave, sounds like the earlier suggestion of checking cables and connections, particularly for that supply, would be worth doing.
Try this if after checking the cables the HVPS test in the FST still fails.
(SCANNER OFF)
To verify the issue is in the channel and not the VDC, just swap a couple of colors. Looking from the rear at the VDC, the order of the connectors from left to right should be B-G-R. Swap red and green. Then do the same at the entrance of the VAA. The order here from the top down is R-G-B. Just swap the two on the top.
(SCANNER ON)
Now run the HVPS test in the FST again. The red channel should show the problem now.
(SCANNER OFF)
Swap all the cables back.
The next step is to gain access to the HVPSs under the optical box. That will require a PARTIAL removal of the optical box. Not a simple job by any means but it can be done under 30 minutes. Verify that the cables coming from the HVPSs into the botton of the optical box are properly inserted.
A couple of extra hands will make the job easier (to hold the optical box) if you decide to replace a HVPS. Otherwise remove completely the optical box. It's safer.
Good luck!
OK, after some weeks dealing with actual life, I'm back to this. I cleaned and reconnected the R, G, and B connections at the VDC, and even removed the optical box to do the same there. I still get the green channel error during the FST HVPS test, about half the time letting it loop. So I'm ready to try the wire swap above for further verification, just one question- anyone know about these connectors at the VAA? I don't want to start yanking on things if there is a trick to them. Manual says nothing. See jpeg.
The only part you have to be careful is the junction of the white cable to the connector itself. So always grab the connector to plug and unplug it, never by the cable. Same thing with ground.
after swap, ran the HSPS test with no failures in any channel. I let it loop 30 times. Guess I'll swap them back again and see where things are at now. Frustrating.
OK, after connections were returned to proper place, it again passed HSPS looping test error free. I then tired a scan with no problems. It's great it's working but the problem remains unsolved. I'm thinking some unreliable connection was "corrected" inadvertently while I was fooling around in there. The only related connections I had not previously cleaned were these at the VAA, which were just swapped twice. Would a unreliable connection there result in an HSPS error?
Last edited by Tyler Boley; 6-May-2016 at 18:53.
Perhaps when you removed the optical box you also moved the connector with issues feeding the HV.
I got the error after moving the box and cleaning those connections though. it only stopped when I swapped leads at the VDC and VAA. I don't know, I guess I'll just get back to work...
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