G07 unusual HV shutdown issue

debaser138

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Back in 2017 I had a G07 that I did a full cap kit and replaced the flyback on and it's been working fine until recently. Now it's going into HV shutdown with the B+ at 170v. I've tested all the normal suspects (FR901, FR401, R908, R902) and everything is good. If I remove X701 it's still in HV shutdown at 170v. I've also swapped in X902, X901, X701, X501, IC501 from my working chassis with no change.

I've replaced the B+ pot, the VR, HOT and even the flyback but no change.

When I fire it up it makes a weird squeak sound and then does it again when I power it off. If X701 is removed the squeak sound is not near as loud and it doesn't make the sound when I shut it down.

Here is a video so you can hear what I'm talking about:


I know it's not the tube or yoke as another chassis works fine on this tube.

Does this sound like a T501 or T503 issue? I've removed/reflowed the solder for both of those and I get a 50 ohm reading on the two legs near each other when I test them.

Any help would be appreciated. Thanks!
 
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It sounds like you confirmed most of the important parts are working.

I would also check the voltage regulator, in circuit is fine.

Edit: I'm sorry, you said you replaced the vr already.

Set your meter to diode test, put the red lead on the red wire of the VR, put the black lead on the other leg, should be .500 ish, keep the red lead on the red wire, and put
the black lead on the outside case of the VR, should be the same, .500 ish.

After that , I'd start beeping out traces from the flyback in all directions.
 
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It sounds like you confirmed most of the important parts are working.

I would also check the voltage regulator, in circuit is fine.

Edit: I'm sorry, you said you replaced the vr already.

Set your meter to diode test, put the red lead on the red wire of the VR, put the black lead on the other leg, should be .500 ish, keep the red lead on the red wire, and put
the black lead on the outside case of the VR, should be the same, .500 ish.

After that , I'd start beeping out traces from the flyback in all directions.

Yeah I already did all that including checking all the traces from the flyback. I think I'm to the point of swapping out T501 first and then T503. I've never seen either of those go bad in any of the G07's I've fixed over the years but there is always a first time for everything.
 
You can easily test transformers without swapping them. Sounds like one of the windings is ok at 50ohmish, how about the other? Should almost be a dead short. Refresh and reflow solder on T501.

In between it working and not working, was the monitor chassis removed at all, or the game moved, where it could have developed a crack? If not, I would think it would be apparent with burn marks on the PCB making the crack instead of movement. Also, with the parts you changed, I would also check for continuity to and from all of those solder joints just in case you have a cold solder, or a bridge.
Can you take a pic of the top and underside of the chassis?

This is a possible horizontal deflection failure. So it will require some troubleshooting outside of the norm.
 
You can easily test transformers without swapping them. Sounds like one of the windings is ok at 50ohmish, how about the other? Should almost be a dead short. Refresh and reflow solder on T501.

In between it working and not working, was the monitor chassis removed at all, or the game moved, where it could have developed a crack? If not, I would think it would be apparent with burn marks on the PCB making the crack instead of movement. Also, with the parts you changed, I would also check for continuity to and from all of those solder joints just in case you have a cold solder, or a bridge.
Can you take a pic of the top and underside of the chassis?

This is a possible horizontal deflection failure. So it will require some troubleshooting outside of the norm.
I would agree and would immediately suspect T501 or a crack or lifted pad on the chassis around or at the flyback.
 
I've seen T501 bad twice I think, both times, there was no reading where there should be 50 ohms. Never have I seen a T501 bad with a 50(ish) ohm reading on the bottom 2 legs of the row of 3 legs. I did
have an odd one once, where it turned out there was a little solder splash that only when it heated up did it make connection (that it shouldn't). So it would run, then the chassis got hot, and the solder splash made
connection between 2 points that were on 2 different pads.

Show us a couple of pics of the top and bottom if you get time.
 
Sorry for the delay on the reply. I got busy with other projects I was working on. So I dug thru looking for bad traces or cracked solder joints on or around the flyback and other areas and I'm not finding anything. I swapped out T501 and no change. This one really has me stumped. I've attached a few pics of the chassis.
 

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I had this same problem a while ago turned out was bad solder joint at R904 - the solder literally wouldn't stick. Had to sand off. Yours looks suspect. YMMV.
 
Is R908 original still? That should be changed 100% of the time (my opinion). I think you said you pulled and tested it already? 47K ohms. How about the 820k ohm resistor right next to it?
 
I had this same problem a while ago turned out was bad solder joint at R904 - the solder literally wouldn't stick. Had to sand off. Yours looks suspect. YMMV.
I checked that resistor and it's good. I also ohm'd the top side of each leg to the next component it connects to and there is perfect continuity.
 
Is R908 original still? That should be changed 100% of the time (my opinion). I think you said you pulled and tested it already? 47K ohms. How about the 820k ohm resistor right next to it?
Yes it was original and tested fine at 47K ohms. I did replace it tho but no change. Resistor R912 next to it tests good. at 820K.
 
I think you said above you replaced the VR and the HOT? Where did you buy them? I've personally had a HOT , test good, in circuit and out, but it was counterfeit, and was causing me HV shutdown.

Edit: I guess this isn't really a relevant comment. It looks like your chassis was working, and then started going into shutdown.

That big resistor R903 ....4.7 ohms, can be measured in-circuit as well. I've seen it at like 13k ohms when it was bad.
 
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I just read something in your original post, you did a cap kit 8 years ago? And depending on the date codes on those caps it could be longer. Certain caps have possibly failed. C411, C516, C517, C511, C701, C520 (bi polar), or C521.

From my notes: "resistor in series with 2ndary flyback winding, for rail of power supply, is a high failure." (R516, R517, R522, or R523?)

If this was sent to me for repair, I would replace the caps listed above, and check solder joints/reflow/measure those 4 resistors. If replacing the caps fixes it, I would replace the others as a preventative measure, even though some of them would probably not need replacing for a while.

So I guess, recap it, check those resistors (including R903) and let us know what happened.
 
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I think you said above you replaced the VR and the HOT? Where did you buy them? I've personally had a HOT , test good, in circuit and out, but it was counterfeit, and was causing me HV shutdown.

Edit: I guess this isn't really a relevant comment. It looks like your chassis was working, and then started going into shutdown.

That big resistor R903 ....4.7 ohms, can be measured in-circuit as well. I've seen it at like 13k ohms when it was bad.
I buy all my monitor parts from ArcadePartsandRepair. I tested R903 and it is good as well.
 
I just read something in your original post, you did a cap kit 8 years ago? And depending on the date codes on those caps it could be longer. Certain caps have possibly failed. C411, C516, C517, C511, C701, C520 (bi polar), or C521.

From my notes: "resistor in series with 2ndary flyback winding, for rail of power supply, is a high failure." (R516, R517, R522, or R523?)

If this was sent to me for repair, I would replace the caps listed above, and check solder joints/reflow/measure those 4 resistors. If replacing the caps fixes it, I would replace the others as a preventative measure, even though some of them would probably not need replacing for a while.

So I guess, recap it, check those resistors (including R903) and let us know what happened.
Yes cap kit was done back in 2017 with caps from APAR. I assume you meant cap C518 and not C516. I tested those caps with my ESR meter and they tested fine but I replaced them anyways with new ones. Even did a new full cap kit. No change.

I checked those 4 resistors and they check out fine out of circuit. One thing I noticed when I was digging around was that R520 was measuring 6.44K out of circuit. Schematic says it should be 5.6K 1/2 watt. I checked the reading on my working chassis and R520 out of circuit measured 6.1K.

The schematic shows it as 5.6K 1/2S. What does the S mean after the wattage? Is it just a standard carbon film resistor?
 
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Sorry was looking at the component layout and saw a cap at C516. But you did a complete cap kit again, and no change.

Yes, I don't know what the S means after the wattage. However it does seem out of tolerance (5600 * 5% tolerance is 5880) so that resistor is failing. Is it the solution, I don't know but it needs changing anyways.

If that doesn't fix it, you can try this. Test for voltage at the base of the horizontal drive transistor (X501). If there is no voltage there, you have no horizontal osc. Test for voltages using this guide here on pins 10, 11, and 12. https://forums.arcade-museum.com/threads/g07-voltage-readings-on-ha11244-chip.305657/#post-2718432.

Unfortunately you may be at the point where you need to check every solder bridge, joint, and continuity for the horizontal and power supply circuits.

If you hit a wall or want to throw it out the window, I can get it fixed for you. Or I'm sure Tron Guy can as well.
 
Sorry was looking at the component layout and saw a cap at C516. But you did a complete cap kit again, and no change.

Yes, I don't know what the S means after the wattage. However it does seem out of tolerance (5600 * 5% tolerance is 5880) so that resistor is failing. Is it the solution, I don't know but it needs changing anyways.

If that doesn't fix it, you can try this. Test for voltage at the base of the horizontal drive transistor (X501). If there is no voltage there, you have no horizontal osc. Test for voltages using this guide here on pins 10, 11, and 12. https://forums.arcade-museum.com/threads/g07-voltage-readings-on-ha11244-chip.305657/#post-2718432.

Unfortunately you may be at the point where you need to check every solder bridge, joint, and continuity for the horizontal and power supply circuits.

If you hit a wall or want to throw it out the window, I can get it fixed for you. Or I'm sure Tron Guy can as well.
Thanks for the info. I'll dig into it again early next week and see if I can figure this out.
 
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