G07 woes...

jb007gd

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Hi all,

Sorry, but the truth is I'm singin' them newbie blues...

Here's my story...
I picked up a Double Dribble with a G07 monitor that chirps when turned on. Okay, I have a flowchart, that means there's a problem with the voltage. The overvoltage circuit is doing it's thing and shutting the monitor down. I replace capacitor C511, no difference. The flowchart says "check all 900s." I test the diodes. They read a junction drop where I expect it but when I reverse my test leads instead of my multimeter reading OL, I get a reading. Every diode I test does this though, and they all give very close to the same reading. "There's no way they would all read the same if they were all bad" I think to myself. "I must be doing something wrong." I move on.

I get to X901 and X902, the transistors. X902 tests just fine in circuit.

X901 in circuit - whoa! Base to emitter - junction drop. Base to collector, same thing. I reverse the test leads. Base to emitter, OL. Base to collector, 1.16? That's the problem right there!

I order a new transistor and when it arrives I dutifully test it. Looks great. I solder it in and... Damn! It's doing the same thing as the old one did! That's when I realize I never tested the old transistor when I pulled it out. Boy was I embarrassed when I tested that old one and it was completely fine...

So now I am left wondering what to do next? My flowchart stops at "test all 900s." I did have the foresight to buy a new voltage regulator (2SC1106). Pulling the one in there to test it looks like a pain in the butt with all those wires going to it, but if that's a logical next step I'll do it.

Any suggestions? And would one of you pros please set me straight as to what my expectations should be when testing semiconductors in circuit?

Many thanks, hope I didn't make you laugh too hard...


- Jay
 
Have you replaced all the caps yet?

If not, I suggest replacing the caps, HOT (2SD870), VR (C1106) and flyback if it is original.

I don't normally hear a G07 chirp. What is your B+?
 
Have you replaced all the caps yet?

If not, I suggest replacing the caps, HOT (2SD870), VR (C1106) and flyback if it is original.

I don't normally hear a G07 chirp. What is your B+?

I would agree with Mod here , deluxe kit this bad boy, otherwise you are chasing your tail, x901 and 902 are vertical drive xistors, shouldnt cause a hv shut down as much as partial or total vertical collapse. only time I have heard a go7 chirp is when I had a flyback with the core cracked in half. do check your B+ before hand too . but if it comes down to it , spend the 40 bone and get the kit with the hot, reg and flyback included
 
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I have replaced all the caps but have not fired it up since doing so. I'll plug it in and measure the B+. If it's within range I'll replace the other parts you suggested. If it's not... you'll hear from me in about 30 minutes! :)
Thank you for the advice!

- Jay
 
I tested and replaced R908 as well and it fired up. Got nothing but a wobbly bleached out screen... B+ measured 119.3. A little adjusting of the vertical hold, focus, and screen control and wouldn't you know it - the thing looks beautiful! Thank you for your help!!! :)

- Jay
 
Well, it should look good for a while - until the flyback blows up (if it's original)....
 
I've tried just replacing the caps and after about 3 diff monitors blew the flyback less then a week after I just replace the flyback at the same time, usually pretty reliable after that

Goodluck!
 
I have had two GO7 flybacks explode directly after doing a cap kit. One was the first power up after the cap kit. Its good insurance to replace the fly before it blows. Luckily they are pretty cheap.
 
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