This log is actually a two-for-one as it was for two seperate monitors (I've been in a monitor repairing mood as of late). G07 monitors are my absolute favorites to work on as they tend to be fairly reliable after being serviced. However, they seem to always have issues with their flybacks. To give a brief summary of what the flyback does, it is the transformer on the circuit board of the monitor that generates the high voltage needed to create a the beam that draws to the phosphors as well as other voltages.
G07 #1 - No Neck Glow/Picture
This one was actually interesting, I had just recapped the monitor and was testing it out. Fired right up, no smoke or blown out fuses and I could hear the high voltage. However, I got no picture. To my surprise I saw no neck glow on the tube, meaning that it wasn't getting the heater voltage. Interestingly enough, there isn't much in terms of circuitry, the heater voltage is derived from a winding on the flyback itself, from there it goes to some pretty standard components that typically aren't failure points
The solution here was just to replace the flyback to see if that fixes the issue. New ones are readily available online from various arcade retailers for ~$30 or so. After replacing the flyback, it confirmed that the the winding was open and not making the 6.3V necessary for the heater, meaning that it had failed gracefully without causing other issues.
G07 #2 - No High Voltage/Blown fuse F901
This one showed immediate signs of damage. First thing I noticed when I looked at the monitor was that the Ferrite Core on the side of the flyback was broken. This typically means that the flyback violently ruptured, typically due to a short on one of the high voltage windings. To accompany this, fuse F901 was blown out, typically this is an indicator of either a bad horizontal output transistor (HOT) or flyback. Upon examining the flyback, I noticed a large crack that went all the way around the flyback. Upon desoldering the flyback more pieces of the ferrite core had fallen out. So it was pretty obvious that this was probably the culprit.
After replacing the flyback and testing the HOT for shorts, as well as replacing F901, it was ready to be tested. It fired right up and was ready to go back into service.
Flyback failures are super common for the G07. Typically these failures happen after the monitor is recapped, not quite sure why that is, but I figure it is do to age and high hours. At least the parts for this monitor are still relatively common and can be obtained for cheap. Two flybacks in one day is not unheard of, I'm just glad it didn't require a whole lot of troubleshooting.
Edited by SNESNESCUBE64