Rebuilt my first G07 But screen goes crazy after 5 minutes of being on?

Parpunk

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Rebuilt my first G07 But screen goes crazy after 5 minutes of being on?

Hey everyone. Ok i did my first rebuild on my G07-CAO Monitor Chassis. I replaced the flyback, HOT, regulator, all caps from BR's cap kit. Powered up and looked great for awhile but then after 5 minutes screen went haywire.? i turned it off let it set for awhile fired up looked perfect, then went bad again after 5 minutes or so. Here's some pics any ideas??>

Oh also i tried messing with all the pots and the vertical size works fine, but the horiz hold and vertical hold dont seem to help much? plus when i turn the horiz. hold pot all the way to the left i hear a high pitched squeal sound?

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ok my hunch is a loose solder joint now after discussing with a few members via pm. Im gonna pull the chassis tonight and check over everything. seems like when it heats up maybe the joints expand and loose connection possibly?
 
Did you check your B+ voltage. My first Go7 cap kit I did I did not check the B+ and it was too high. Picture looked fine but about 15 minuets and one of the caps exploded because the voltage was too high. :eek:
 
woah no i never checked it! how do i check it??? what do i put the meter on and whats the correct voltage on it?
 
Black on the frame, red on R901, the big resistor on the left side as you face the back. The lead closest to the tube. Should be ~120VDC.

If it's less - a lot less - check R908 to see if it's open.

If it's more - a lot more - check X901 and X902.
 
Ok my evening has already started bad !.

Get home from work anxious to test the B+. After checking out my manual for the G07 Monitor CAO Chassis the B+ on this particular chassis is at the back of the chassis and very easy to reach from the back of the cab. Bascially its a little pin sticking out of the board with a wire wrapped around it that runs straight to the regulator. However this pin is very close to the edge of the metal frame as well. (i didnt have alligator clips and was relying on a steady hand) yes im a stupid newbie!

So anyways get home, turn on machine and still garbled picture (not even getting the nice picture like i was after i first put it back in the chassis. However garbled picture was moving extremly slow this time and just inched across the screen.

Anyways i turn the B+ voltage up and the image starts to go across the screen very fast so i turned it back down.

Then i go to test the B+ and my first testing was 106.1 Vdc. So i go to the B+ turning pot and turn it up just a hair.

I go to test it again and it comes out at 150 something Vdc (too high!)

I then turn the B+ back down just a hair.

go to test the B+ again and after i put my positive lead on the wired pin, i slowly look down at the meter and the positive lead touches the metal chassis! spark flys scares the crap outta me. And now i feel i might have shorted something. Help!

I go to meess with the B+ pot and no matter how high i turn it the B+ will not go any higher than like 95.6VDC to like 98.4 VDC or something similar.

Could i have shorted my regulator? What should i do know? :-( The wire runs straight from the B+ pin to the regulator.

BTW i checked the big block white ceramic resistor by putting my DMM on Volts DC and am getting pretty much 0VDC when i put the leads on both ends. Even when i switch them back and forth. However i am doing this with the machine off,....... is that the way its supposed to be done?. I was actually getting about 0VDC before i ever put it back in the cab though too, so i might have been doing something wrong.

Also i noticed that everytime i would move the big joystick the screen would jump and react to my movement?

Where do i go from here?

Any help would be great. thanks!
 
Yes, you will get zero volts when your machine is OFF.

You have a problem with your chassis. See my post directly above yours.
 
do you have a G07 chart anywhere that shows where those are at? I cant read them on the board while its in the chassis?
 
thanx for the links! As for right now after last nights incident tried to turn the machine on and it took like 3 or 4 mintues before the monitor came on. So im thinking since last night the B+ is very low now and taking forever to power up possibly? Im gonna pull it tonight and check all my solder joints and check those resistors if i can find where they are at. I guess the power has to be on to check the volts in the resistors?
 
NO. You don't check the volts in the resistors.

Set your meter for Ohms. You will have to desolder one leg of R908 to meter it properly. One lead on one leg, the other lead on the other. Note the rating. If it's open...replace it.

You may want to have someone that deals with this a lot fix it for you. If you'd like me to, PM me.
 
Im gonna try and figure it out and if i cant then i will have you fix it for me. I just want that sense of accomplishment that i brought this thing back to life completely from being dead and i feel that im so close just a few more hurdles.

Im gonna check the voltage on the R901 tonight, then depending if its higher or lower than the 120VDC im gonna then pull the chassis and check those resistors. Then recheck all my solder work, and inspect the pots to see if one of them is broken or not.

Then after all that if it doesnt change i might have to call in the big guns (you) :)
 
If it's happening consistently after the monitor has been on for a while, it might be something breaking down once it heats up.

Get some freeze spray (or duster spray and turn it upside-down) and spray it on the components on the board once it starts messing up. Pay attention to transistors and ICs especially. Once you hit the problematic component, the screen should clear up again, then go back once it heats up.
 
its doing it constantly now, everytime i turn it on now the picture is all garbled and even bending in on the sides and racing across the screen real fast, and then sometimes slow
 
That must be TARG!

(or SPECTAR!)

One issue you may be having is that the horizontal oscillator may be WAY off after replacing some caps in one of the related tuned circuits. I think there is a procedure for roughly setting the Hfreq so that the horz freq control has better fine-tuning control of it.

So, get the B+ set close and then look at this.

Bear in mind that the manual wants the monitor to be warmed up before setting any of these adjustments.

Kerry
 
IT is TARg It Is TARG! lol

Do you know the Horizontal Frequency Procedure or know where i can read about what you mean?
 
OK- I read that this is a G07- no oscillator adjustment for this except for the hfreq pot. (I was thinking about the 4600 where there is a little coil that you adjust..)

It sounds like you were reading 0V from one side of the resistor to the other side. You're supposed to be measuring from the metal chassis ground to the far side of it. You may have zapped something when you shorted your lead, but just check again.
 
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