G07 - Perfect B+, Neck Glow, No pic?

modessitt

Volunteer: Encyclopedia Submission Moderator
Joined
Mar 22, 2007
Messages
33,414
Reaction score
325
Location
Austin, Texas
Been trying to help a fellow KLOV member over the phone. He had a working G07 that he recapped, new flyback, new width coil, new HOT. He said it worked for a few minutes, then went dead. He had some high B+ (shutdown) that I helped him diagnose. Now he has a B+ of 119, neck glow - and no picture. I had him try multiple things but he's not getting anywhere, and isn't ready to send it to me yet. He gets a small spark on discharge, but isn't hearing it power up with static. I had him do continuity checks from all the flyback pins to check for cracks, as well as from all the neck socket pins. At one point he said he saw a "purplish glow" between the white wire from the bottom of the flyback and the white wire coming from K2. I had him separate them and wrap them in electrical tape for safety, but still no pic.

Right now I have him checking another game he has to see if it has a G07 that he can swap to this tube to verify the tube didn't become damaged somehow. Anyone else have a bright idea that I'm not thinking of? I'm sure I'd figure out if I had it here...
 
R908 bad shouldn't give good B+ and neck glow, right?

I had him check the neckboard and he found one spot he touched up, but that didn't help...
 
Not for the easily freaked out.

Sounds like the flyback (even though its new) is poo poo. You said he doesnt hear much in the way of the static upon power up and only gets slight pop when discharging. What I would do is put my high voltage probe on it but if he doesnt have one heres the other thing I do...

Pop the high voltage anode off of the tube (while the power is off). Place the anode in a position to where the lead is about a 1/4 of an inch away from the metal frame of the monitor and turn it on for a second or so. You should get a pretty good sized spark coming from the anode to the frame and it should be pretty noisy. If its not then I think that new flyback is done for.

I've also used a grounded screwdriver under the cap while its still connected to the tube to do this. The trick is that you cant ground out the anode or you'll fry something.

I know, sounds crazy but it gets the job done.

Wait... Isnt there a circuit on the GO7's that will kill the video under certain circumstances? I seem to recall a transistor that was able to kill all video.

Dumb question incoming... He has tried to turn up the screen control right?

EDIT: X303... Beam limiter. Or if some how he's missing +12 on the 6 signal amplifiers before RGB hits the neck board. I think theres a Zener off of the flyback that creates that +12. Its been a long time since I've had to fix a GO7. Some times I'm envious of you guys that fool with this stuff day in and day out.
 
Last edited:
R908 bad shouldn't give good B+ and neck glow, right?

I had him check the neckboard and he found one spot he touched up, but that didn't help...

Not necessarily Steve, have him fire up the monitor and quickly look at the center of the screen. Does he see a small prism of color that fades away to nothing? Change the R908, i've seen some of the weirdest shit come out of bad 908's or a corrupt IC chip on this chassis that no flowchart could ever explain. It'll take less time at this point to change a couple parts than it will to seek out the problem with a meter.
 
Last edited:
R908 going bad? Bad solder on neckboard?

Andrew

Curious. I dont see r908 on the schematic I downloaded.

Oops.. Looking at the wrong schematic. 908 has something to do with the X ray shut down, right?
 
Last edited:
I've had R908s that have tested fine, but once replaced the monitor worked. *shrug*

Me, too, but never with perfect B+. Usually the B+ will be very high or very low, not spot on.

I told him to stick the old flyback back on to see if it was the flyback - and he'd already thrown it out. :rolleyes:

He really just needs to bite the bullet and send it to me...
 
Fixed. Bad flyback. Looks like one of the new ones from Bob, replaced with the same. I pulled it and checked it with my ring tester versus another, and it checked out, so I reinstalled and it still didn't work. So - I swapped in the new one and it works just fine...
 
Back
Top Bottom