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G07 Monitor flyback issues

SNESNESCUBE64

Entry posted by SNESNESCUBE64 in Arcade Monitor Repair

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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.

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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.

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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

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spacepup

This pretty much flew over my head "whoosh!" but nevertheless, I think it's awesome that you did it and shared this here.  I'm sure other people who are more knowledgeable about this stuff will also find it interesting. 

I love the passion you have for this stuff - keep up the great work!

 

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SNESNESCUBE64
5 hours ago, spacepup said:

This pretty much flew over my head "whoosh!" but nevertheless, I think it's awesome that you did it and shared this here.  I'm sure other people who are more knowledgeable about this stuff will also find it interesting. 

I love the passion you have for this stuff - keep up the great work!

 

I appreciate the kind words. I'm trying my best to make these so that new folk can maybe do more themselves as paying a tech is expensive. If it went over your head, maybe I need to rethink how I go about explaining my process. I've been doing it a while and some things that are common sense to me might not be for others...

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SNESNESCUBE64
45 minutes ago, docile tapeworm said:

you know how to adjust convergance with magnets?

Convergence is rough. There are two types of convergence, static and dynamic. Static is where you adjust the three sets of rings on the back of the tube. Dynamic is where the yoke is not aligned, this will typically cause warpage on the corners/edges. Magnets/convergence strips should be used only if you are having convergence problems in the corners.

Even so, adding convergence strips and magnets should only be used if you can absolutely not live with it and you've already have done static and dynamic convergance alignment. The scary part about doing this, is that it is a pain in the butt to do magnets, it involves sliding strips into the yoke while the monitor is on, which poses risk of shock and serious injury as you need to see what changes when you add the magnets. I wouldn't try to add magnets unless you really cannot live the inherent flaws with CRTs. Unfortunately I don't really have a whole lot of advice to give, its all experimentation.

These strips can be purchased online, I bought a ton a while back to have them on hand. If you do choose to adjust convergence, make sure you mark the rings with a paint pen so if you make it worse, you can always go back. Pages 6 and 7 of the K7000 service manual has a really good explaination of setting up convergence:

https://www.google.com/url?q=http://www.arcade-museum.com/manuals-monitors/Wells%20Gardner%20K7000%20Manual.pdf&sa=U&ved=2ahUKEwj11MX8wtnyAhWHXM0KHR8gBnoQFnoECAIQAQ&usg=AOvVaw2VXkXr7Orf5alpJLoZ80Vl

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docile tapeworm

@SNESNESCUBE64 thank you for your time. i have a panasonic tau 20sl15 that has some geometry issues on the left upper side. its not in the corner or on the boarders its kinda in the center of the tv still. i did get into the service menu and was able to adjust it but its still "wonkie" in that spot.

i realize crts are perfectly imperfect. and you have to live with some of the geometry issues.

i also have a toshiba 20af44. the service menu is elementary. no pin/yoke adjustments only vert and horizontal. i got it decent though. i would have to take the shell off this one.

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SNESNESCUBE64
2 hours ago, docile tapeworm said:

@SNESNESCUBE64 thank you for your time. i have a panasonic tau 20sl15 that has some geometry issues on the left upper side. its not in the corner or on the boarders its kinda in the center of the tv still. i did get into the service menu and was able to adjust it but its still "wonkie" in that spot.

i realize crts are perfectly imperfect. and you have to live with some of the geometry issues.

i also have a toshiba 20af44. the service menu is elementary. no pin/yoke adjustments only vert and horizontal. i got it decent though. i would have to take the shell off this one.

Part of the charm of CRTs is its imperfections. Unfortunately some of these adjustments require use of magnetic strips. Everytime I've done it, its been just trial and error. I recently did it with my Bubble Bobble monitor, that required a lot of strips to 'fix' the bottom, unfortunately its not perfect but its a lot better. Good luck with your endeavors, maybe next time I need to screw around with convergence, I'll do a log or a video on how I do it.

This video does a pretty decent job at explaining how to do this: 

 

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