Donkey Kong killed my 19'' Electrohome G07

[MaineEvent]

After capping my chassis I had everything beautiful and working. My brother and I were enjoying a few brews and playing several hundred games of Donkey Kong  ...While he was playing the screen all of a sudden went black and all that was present was a small blue dot in the middle of the monitor. UGHHH!
I was hoping it was just a blown capacitor at the time, and maybe I could replace it and get er' back up and running again.
So I opened the cab up, it was pretty warm inside but I wouldn't say it was hot....warning sign?
I discharged the monitor,waited a few minutes, discharged, and repeated one more time.

I took out the chassis and started checking the caps with my multimeter....and got a small shock when I inadvertently touched the frame and the bottom of the board.....weird?

I metered the power cord that connects to the transformer and the board was clearly holding a charge! My brother knows more than I about electronics, and he figured it was the coil or flyback holding it.... I agreed and he said we should try and discharge it just in case.... So I took a screwdriver and touched it to the frame of the chassis and botton of the board.... in my brilliance I decided to touch it to the bottom of the biggest greyest capacitor looking thing on the board..bad idea? ( I have metered this thing too and it appears to be fine)
SPARK
Cool energy is gone, lets figure this out..
We figured out that c523 was bad....but when I replaced it and put everything back together nothing happened.... I didn't get the familiar high pitched whining sound of the monitor, it is completely black as if it is not getting any power.

I have since taken the chassis back out to change c523 again with another working cap...but that didn't help.
I metered c905 and it seemed to be dead too.... so i switched that, but still no change
I inspected the 2 fuses on the board, they look fine and nothing looks melted or strange.

Once again I am at the mercy of the forum 

[qrz]

i assume you checked the fuse to the right of "the big grey cap".

it is a secondary fuse , and if the afore mentioned cap is retaining voltage , the fuse is likely open.

also check the h output stage .....shorts/poor connections etc...

[Kevin Mullins]

There are so many things wrong with that original post..... 


Look to see if there is a crack anywhere on the flyback.

[MaineEvent]

Alright.... So the flyback isn't cracked....
And that secondary fuse looked OK, but doesn't have any coninuity. So would that be what caused my monitor to shrink into a blue dot and then give nothing when I turn the game on? On the board it says it's 1.25A 125V. It would be great if thats all that I need to replace!

[Kevin Mullins]

That fuse is a good place to start....... but whether or not there was a cause is the question.

[MaineEvent]

So I replaced the 1.25A fuse and now when I turn it on I hear the soothing high pitched whining sound! But still a blank screen that I can play blind.......

[Kevin Mullins]

Check the H.O.T.
2SD870 if I recall.

It's one of the two large metal transistors mounted on one of the big heatsinks.
X01 by the flyback.

[MaineEvent]

Alright... So my HOT is ok, but the power regulator on the other side was done. I replaced that and a resistor (R415) it's a 2.7K OHM 1w ( these don't need to be soldered in a certain direction like caps do they?)

And still nothing when I turn it on. No high pitched whine from the monitor, no neck glow... I'm considering blasphemating my cab with a free computer monitor, just so I can play the damn thing.

Thanks in advance

[StephenH]

You may want to e-mail Rick Nieman at rick@niemandisplays.com.   I heard he was the original designer of the G07 when he used to work for ElectroHome.

[Kevin Mullins]

There are TWO fuses on a G07, are they BOTH good ?

Did you check the entire chassis for bad solder joints and cracked traces while you had it out ?

[SirPeale]

Aha...you do have a thread about this.  You haven't updated it recently. 

You need to check the B+.  Meter set for DC, Black lead to the frame, red lead to the tab closer to the tube on the large white resistor on the left (as you face the back).

If it's 120VDC, that's good.

If it's lower (like, a LOT lower) it could be X901 or X902. 

If it's higher (150VDC) unsolder one leg of R908 and see if its gone open.

[MaineEvent]

Yep both fuses are good, and I scanned that thing hard for bad solder joints and cracks

Okay,

I threw the flyback back in there  (it is a white-ish one, with lots of dust and dirt) and tested the B+ as explained (thank you  )
And I came up with 47.5VDC on the leg with the connected wire, and 150VDC on the opposite leg....
Can I just adjust the B+ pot ? Or should I order the X901 and X902 parts now?

Thanks!

[SirPeale]

Test those parts, but especially test R908.  If it goes open, it can cause symptoms like you're having.

[MaineEvent]

R908 tested good, 46.x K
I wasn't sure how to test something with 3 legs, but I got a good continuity on X901 and X902 from 2 legs
Is it possible my tube is bad? I can't remember the last time I saw a glow in the neck tube...

[SirPeale]

If it goes into shutdown the heater won't light.  Likely your tube is fine.

I hope this helps a bit:

http://www.hobbyprojects.com/test_and_measurement/testing_transistors.html

I generally use the diode test to test them.

[sinastar]

is this an original donkey kong cabinet if so how are you getting power to monitor,,  ge07 should be hooked to isolation transformer .. the one that came with the game is wired to put out 100volts for the old sanyo that was in it...so you should have new transformer installed for the ge07 that has 120 output,, if ge07 is hooked to the original nintendo transformer or without an isolation transformer it will damage the monitor