27K7391 No Video

Cyberwhiz

New member
Joined
Aug 5, 2007
Messages
83
Reaction score
0
Location
Braselton, Georgia
WG 27K7391 Has raster but no video

Looking for some help on this monitor. Original problem was missing colors, don't remember which ones. Anyhow, after a cap kit, still had same issue so I ordered the neckboard transistors after verifying that the passive components on the neckboard were good. Once I finally got the transistors, I hooked the monitor back up to see which colors were missing and got no video at all. Went ahead and replaced the transistors (2) anyways but same issue. Turning up the screen control, I do have raster lines and the B+ is at 130v. So, following Fromm's Flowcharts, I replaced Q4 and Q7, with no effect.

When I turn up the screen control, the raster lines are there but I don't see the game playing at all. I hooked up another monitor to the test rig and it worked fine. This is the 27K7391 with the pincushion adjustment board. No amount of fiddling with the screen adjustments produces an image.

Thanks in advance.
 
Last edited:
I'm assuming you resoldered all the header pins on the video input connector ?
Common failure on a K7000.

Heater voltage good ?
 
voltage regulator running a little high. shouldnt it be at 123v? which side of the sand resistor are you measuring at.

put your finger on C57. does it feel like it has a dome on it? if so replace.

test IC4.
 
voltage regulator running a little high. shouldnt it be at 123v? which side of the sand resistor are you measuring at.

I think 123v is 19", This monitor has the STR30130 HOT so I believe 130v is right on (?)

put your finger on C57. does it feel like it has a dome on it? if so replace.

test IC4.

C57 was replaced when I did the cap kit, of course that doesn't mean the replacement isn't faulty so I'll check again.

Thanks for the ideas!
 
Last edited:
is this a standard k7000 (older) and not the more modern k7000??

if so, check both of the blue and white ribbon cables that go from the bwxkboard to the chassis.. if some of those wires are open( ends do come apart sometimes) then theres your issue. My fix is always to just remove the connector, then strip the end of the wires and place the wires through the holes in the board and solder togther...
 
I followed the suggestions made and reflowed the video connector and the blue/white harnesses. I didn't see any frayed wires but went ahead and ohm'd out the wires pcb to pcb just to be sure. After all that, same symptom: raster but no video.

Cadillacman: the board is a 1993 vintage P538.

I can't help but think that this is something simple but I just can't nail it down. Any other suggestions ?

Thanks!
 
Last edited:
Check to make sure the color voltages are actually making it to the neckboard first. Then verify that the caps are all in properly, especially the one on the neckboard if your model has one....
 
Back
Top Bottom