Another G07 dead

roburt

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Hello to all. What I've got is an 1981 Centipede with a G07 chassis. It was doa. Got it to play blind & found a cracked flyback. Ordered a cap kit, hot, flyback, & fuses. Installed said items, reflowed headers, and checked my work and still no neck glow. Followed the flowchart & now I'm not sure what to do (first time working with a monitor). I have 110 to chassis. Both transistors are not shorted. Both chassis fuses are still good. I'm getting 119.6 vdc at the big resistor (white wire) and 165.5 vdc at the back end. Flowchart says it should be around 120v & 145v. I am also hearing some hissing from the chassis. I turned out the lights & see nothing but darkness. At this point, I'm lacking direction. I'm looking for some advice before I redo everything & try again. Any imput would be very much appreciated. Thanks.
 
EDIT - I should have asked the simple questions first. Do you have neck glow? Have you tried turning up the brightness on the flyback? A lot of monitors will need that adjustment after a rebuild.

Double check all the caps for proper polarity. That hissing might be a cap that popped from being in backwards (anything stink?). It could also be caused by a loose wire under those rubber insulators on the back of the focus pot (check them with the power off!), or even a loose wire where it connects to the neck socket from the focus pot.

And if you get 119 at the resistor on the left, then that's good B+. Is the 165 what you measure on the case of the HOT on the right? Also, make sure the legs of the HOT and VR aren't touching (or very close) to the side walls, and that you put the mica insulators in there when putting them in.

It might also be a good idea to check that you put the wires on the VR and HOT back on properly...
 
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No neck glow at all. the 165voltage is from the back of the big white resistor (red lead) & chassis frame (black lead). I will double check the legs on the hot & wires on the focus pot. Being new to this, anything is possible. No smells at all from the board. I'll double check polarity again too. While rebuilding, I had a weird gut feeling about the Horizontal Output Trans. That's the first thing I'll check. Thanks.
 
165VDC is "normal" at the other end of the resistor.....The 145VDC in the flowchart is wrong.
Have you tried turning the "screen" control all the way up?

Edward
 
Double check cap 302, famous for having the polarity screened backwards on the board. If you matched the new cap's polarity to the old cap then you should be fine.
 
Double check cap 302, famous for having the polarity screened backwards on the board. If you matched the new cap's polarity to the old cap then you should be fine.

Hehe - yeah, or rather, it's screened backwards on ONE SIDE of the board. IIRC, the screening on the top of the board is correct, but the markings on the bottom of the board are not.

-Ian
 
I saw the incorrect screening on the backside of the board. 302 is in correctly. Good call on the focus pot. I found a loose wire under the rubber bootie. It was the yeller one. My hissing went away after that fix. No "popped" caps that I can see. Still no neck glow & I have adjusted the screen all the way up & all the way down just to see if it made a difference. Didn't think it would if I've no juice to the monitor. After work tonight, I'm gonna pull the chassis again & re-double double check it.
 
"Neck glow" is the heater. The voltage comes from the flyback on an Electrohome. There's only two or three componets in the heater circuit....maybe a broken trace?

Edward
 
I pulled the board ...again. Went over everything I could think of. Found nothing. I believe there is no high voltage to the tube. Nothing to discharge when I removed the anode wire. I re- re-double double checked my fuses, HOT, solder joints, and voltage at the white resistor. All okay. Still no heater. I'm going to pull it again & really look over the neck board. When I tried to power up, I heard nothing unusual, & smelled nothing (other than myself). How, where do I check the flyback to see if I'm getting voltage there. I do not have a HV probe, but a pretty good DMM.
 
R902? I'll check into it if I can find it. I've found I've got 265 vdc to the yellow wire from main board to the neck board, but can't follow it much from there. This thing is really starting to get to me. A little frustrated...can you tell?
 
Turn the chassis over and look at the bottom. R902 is on the edge of the chassis in the center opposite the side from the fly.
 
And check R908. Sometimes it'll go open. it's supposed to be 47k-ohms, but sometimes it measure at about 11k-ohms in circuit, so you may have to pull a leg to test properly...
 
I've checked R902, R908, R901, C905, but have a dent in C511 from bob roberts kit. Not sure how to check a cap. Dented, I'm thinking 50/50. What values should I look for with R902 & R901? Found no broken traces. PITA, but I went through as much as I could.
 
r908

Fixing a Mrs.Pacman with a g07 monitor. We replaced the power supply, and re-installed everything monitor did not work. Pulled out the chassie and replaced the flyback transformer and the two fuses. Re-installed and everything worked minues red and the monitor had a horrible burn in, so we decided to replace the tube. We took the old tube out and replaced it with a 19" t.V, the only problem is the wire come from the yoke are differnt colors. On the original Mrs.Pacman tube, the wire colors grey,red,brown, and white. And on the new tube the colors are red,blue,yellow,green. Which is the correct color matching for the horizontal and veritical widing?

After re-installing everything to what we believed to be correct we blew a tube and replaced it. Checked to see if we did any damage to the chassie and the two fuses were blown again the flyback transformer is cracked again and there is no reading off the r908 at all.
 
This should really be in a separate thread, but it sounds like you blew it up because you used the wrong yoke, and the yoke was hooked up wrong.

When swapping a tube, you MUST make sure to swap ONLY the tube. The yoke from the old tube MUST be put onto the new tube because it matches the chassis. If you put the chassis with the wrong tube, then you get fireworks. Now you not only have to put a G07 yoke on the new tube, but you have to do some major repairs to the G07 chassis.

As for the yoke connections, G07's used a different pattern for their yoke pinouts. The red and white wires are for the horizontal yoke, and the grey and brown wires are for the vertical yoke. For the 5 pin yoke connector, IIRC the order goes from left to right:

grey-white-brown-empty-red

I might have the grey and brown swapped, so if the picture comes up backwards, just swap their positions.

On the other yoke, btw, the red and blue are horizontal and the yellow and green are vertical, and would normally go:

red-blue-yellow-green

IIRC....
 
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