AVS Forum banner

Status
Not open for further replies.
1 - 5 of 5 Posts

·
Registered
Joined
·
4,916 Posts
Discussion Starter · #1 ·
Here is the deal:

Last evening the R CRT refused to display video when I turned it on. Subsequent turn ons and it finally came on and operated OK.

Well the problem has become worst and now I am trying to diagnose what is causing this. The tube light's OK but no video. In fact you can see the tube get brighter and dimmer as the scenes change....but no scan lines. If I take the Red video in and put in into the G neckboard, it displayes it so I definately have video coming to the neck board. I have tried changing the Red neck board and the CRT and neither change the symptom. While I was at it I also changed every plug in board but the System PWB just to see if there was any effect. Still nothing. Could this be a System PWB problem?? A reset perhaps??

I have looked over the block diagrams in the service manual and this really doesn't look that comlicated. Problem is the unit is on the ceiling and I guess I am looking for a quick fix to avoid having to haul it down and work on it in the shop.

Any ideas. Thanks in advance for any suggestions.
 

·
Registered
Joined
·
2,837 Posts
Stop using the machine now. Your symptoms sound almost exactly like what was happening to my machine a year ago when its vertical deflection board went bad. My symptoms were in the green gun and it also showed no raster but did light up the ENTIRE phosphor like a flood beam tube. It too went up and down in light output with video. Unfortunately, operating the machine for several minutes with fault lead to a catastrophic failure. The errant beam energy overheated and snapped the tube neck. The snapped tube neck, cut through yoke windings. The cut windings took out several more boards in the machine. Proceed with caution. At the very least turn contrast way way down while diagnosing with swapping the neck boards. That should reduce the risk of a thermal tube failure. Personally, I'd haul it in and not play with it yourself.
 

·
Registered
Joined
·
3,902 Posts
Yeah, but Terry's got a spare vd board he can swap in to check it. (maybe two)

Even with Contrast set low it should be a quick diagnose.
 

·
Registered
Joined
·
1,214 Posts
Quote:
Originally posted by Guy Kuo
Your symptoms sound almost exactly like what was happening to my machine a year ago when its vertical deflection board went bad. My symptoms were in the green gun and it also showed no raster but did light up the ENTIRE phosphor like a flood beam tube. It too went up and down in light output with video. Unfortunately, operating the machine for several minutes with fault lead to a catastrophic failure. The errant beam energy overheated and snapped the tube neck. The snapped tube neck, cut through yoke windings. The cut windings took out several more boards in the machine...
REALLY?! Wow, that's really odd. But an easy way to check this would be to swap red and green vertical yoke plugs and see if the problem switches to green.


Chuck
 

·
Registered
Joined
·
4,916 Posts
Discussion Starter · #5 ·
Taking out the Vertical Deflection board was not something I was going to do with the unit on the ceiling. So this one is going to take a back burner for a while and I took the unit down and used it as a parts machine for now and hung a 110LC. When I get a chance to put it back together I will try what you are saying Chuck.

Thanks for the advice.


Terry
 
1 - 5 of 5 Posts
Status
Not open for further replies.
Top