jb007gd
New member
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
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