Help! Something blew while adjusting H.FREQ on G07

Finch

New member
Joined
Apr 27, 2006
Messages
104
Reaction score
0
Location
Santa Cruz, California
So I've got a newly capped/flyback/hot/H width coil G07 and I was trying to adjust things a bit in order to get a clear picture. I never touched the adjustments from when I got it, where they supposedly were set right, but after the cap kit and everything it's just crazy scrolling pictures that look slanted horribly in one direction.

I had the monitor hooked up to a RGB modded sega genesis as it's the only working hardware I have that outputs RGB. Anyways as I'm adjusting the H.FREQ it makes a nice pop/sizzle sound, a very small puff of smoke somewhere in the vicinity of the base of the flyback and now nothing. Also looks like it blew the small fuse next to the big cap. Can adjusting the H.FREQ too far cause damage? I wasn't cranking it like crazy or anything, but it popped when I turned it further than before, which seemed to be helping the picture.

Course of action? Or any experience with this?
 
If you're overdriving the horizontal oscillator, then it can certainly damage the chassis. If you blew the small fuse, make sure to discharge the filter cap (discharge both sides of the fuse) before looking into it. (Expect a big BANG!) You probably blew the HOT for sure, and maybe burned up a resistor, diode, or transistor there somewhere (the smoke).

I don't know much about a modded Genesis as a signal generator, so I'm not sure if the issue was caused by the signal or a problem with the chassis. I'm also not sure if the RGB being put out by the Sega is a standard-res 15kHz like the G07 is expecting. If it's putting out something in the 25K (med-res) to 31k (VGA) - or even NTSC (TV), then that would definitely cause the scrambled pic and damaged components.

What were you planning on using the G07 for if you have no games that output RGB at standard-res for testing? Were you powering it with an isolation transformer? What was the B+ with no video signal applied?
 
The genesis outputs 15hz 240p, so it should be ok, unless there is some other issue with it's sync signal.

I have a non working gorf board, and haven't bought the galaga Pacman reunion board I'm planning to run on it, so the genesis seemed like a good stand in for the time being.

Didn't test the B+ without a signal, how does one go about doing that?

Yes it had an isolation transformer.



Ugh, when I fix it....again is there anything I should look out for when adjusting it. I just replaced the HOT and all sorts of stuff, can't wait to do it again. Is there any sort of guide out there for what to do when adjusting these? Like what you should adjust depending on what the image is doing. Never repaired a monitor before so I'm at a bit of a loss.


:-(
 
Last edited:
Forget the Genesis. If you get it fixed again, just power it up, check that the B+ is 120, turn the brightness up to see that it has raster (white screen), then wait until you have a regular game to hook it up to...
 
The Genesis should work though. It's outputting 15khz RGB.

Are you sure you had the sync connected correctly though? The Genesis should be negative sync.

-Ian
 
The Genesis should work though. It's outputting 15khz RGB.

Are you sure you had the sync connected correctly though? The Genesis should be negative sync.

-Ian

I hope so. It was connected to the same pins Gorf uses to sync, which I think is J2 and J1, which are jumpered together on the harness.

Probably should have researched this more before adjusting things. At least I probably fried less than all the caps and flyback, so at least I don't have to do all that again.

Probably going to discharge everything later this week and poke around to see what blew and try to repair it. In the meantime I should probably get a way to just hook up a spare Neo Geo board, incase the Genesis is an issue, although sounds like it should be safe since its 15hz 240p.

If anyone has any guesses as to exactly what might have burnt out, it would be greatly appreciated.
 
Got around to popping the chassis out and testing stuff. Interestingly the big filter cap had no charge, neither did the anode cap. Although it has been a week since I killed it, but I figured the filter cap would have something since it's fuse blew.

Anyways, the only thing I can find that died is the fuse and the HOT. I know something popped and smoked over near the flyback, but I can't tell what. Any ideas? I've checked all the other transistors and I think they are fine. I just figure smoke and a pop means something died. Is the flyback fine when It was just caused from overdriving the H.FREQ circuit?
 
Back
Top Bottom