How can you tell if the flyback is bad?

Stuffmonger

Member
Joined
Jan 12, 2007
Messages
918
Reaction score
7
Location
California
I have a couple 19" monitors that aren't working. On both of them, there is proper voltage going to the monitor, and no blown fuses. Neither one hums or has glow in the neck. I checked one last night with a voltage tester like in the picture attached, but since it only sees AC voltage, it didn't get very far. So, how can you tell when the flyback is shot?
 

Attachments

  • gt-16.jpg
    gt-16.jpg
    4.9 KB · Views: 22
If it has cracks in it or lightning is shooting out, then it's bad.

Otherwise, there are a lot of other things that can make a monitor be dead, including a bad flyback without cracks or lightning.

First thing to do is identify which model chassis you have. Then get a digital multimeter and learn how to use it. Then come here for advice if you can't figure out what to do next...
 
If it has cracks in it or lightning is shooting out, then it's bad.

Otherwise, there are a lot of other things that can make a monitor be dead, including a bad flyback without cracks or lightning.

First thing to do is identify which model chassis you have. Then get a digital multimeter and learn how to use it. Then come here for advice if you can't figure out what to do next...

I have a multimeter, and use it often/am familiar with it. I don't see how the model of chassis really makes much difference since the same thing is happening on 2 different models of chassis. I'd think there would be a general idea of what may be wrong since most monitors have similar components, but I'll get the chassis numbers if it really will make any difference.
 
It definitely makes a difference what kind of monitor it is. Different monitors are built differently, and have different track records of flyback failure. For example, if it's G07 and it's dead, then I'd tell you to check the small fuse and the HOT, and if they're blown, replace the flyback, HOT and fuse. If it's a 4900 and it's dead, then I'd start at the B+ circuit.

The flyback is not the main failure in all monitors. And I don't know where you were waving that voltage tester, but don't EVER try to measure the output of a flyback transformer without a special high voltage probe. That's 20,000 volts. To check for the presence of HV, just listen for static, or put the back of your hand up to the face of the tube. You can feel the HV move the little hairs on your hand. Alternatively, a small scrap of paper should stick to the tube.

I'd suggest finding out what kind of monitor you're dealing with, and start from there. Use the forum's search function to look for information. Read the schematic. Check voltages on the chassis, ensure the B+ is correct, etc.

-Ian
 
One is an electrohome-G07 chassis
The other is an MQ-29 I think.

OK, the Electrohome, check the small fuse, and check the HOT. If the small fuse is blown or the HOT is shorted, then you need a flyback. On these monitors, just shotgun them - all new caps, new flyback, new HOT and small fuse. Be careful of the width coil, don't break it.

I am not familiar with the MQ-29.

-Ian
 
OK, the Electrohome, check the small fuse, and check the HOT. If the small fuse is blown or the HOT is shorted, then you need a flyback. On these monitors, just shotgun them - all new caps, new flyback, new HOT and small fuse. Be careful of the width coil, don't break it.

I am not familiar with the MQ-29.

-Ian

How do you check the HOT?

I'm getting pics of the MQ-29... it's a strange chassis... Flyback is not on the pcb, and has 4 different connections. The cab was a centipede at one point, but I doubt the monitor is original.
 
So... Better to just buy a new chassis then, I suppose.

Maybe, or you can track down the missing cards and get it all fixed up. The 4600 is a good monitor, but a fair amount of work to get running good. They're notorious for their bad solder joints at the pins for the cards, and the cards themselves can be troublesome.

Don't throw it out though, maybe some day you'll stumble onto the parts you need. Or, maybe someone else could use it. Speaking of which, I really need to sort out the 4600's I have. I think I have two and a half wrecked ones, should really get to rebuilding those.

-Ian
 
Well. Thanks for the info guys. Looks like it was the short fuse that was bad on the g07. It was hiding from me. I'll probably do what was suggested and get the full cap/flyback/HOT/fuse kit from bob roberts, then at some point, I'll get a new chassis (and shelf the k4600) for the centipede cab... or just get rid of it for someone else to restore.
 
if the fuse is blown on the Go7, that capacitor can still have a charge in it ready to zap you
take your discharge tool and touch both sides of the fuse holder to discharge the capacitor

if you dont know what a discharge tool is or how to use one, do a search here and read or you might find out the wrong way what its like getting bit by a capacitor feels like

the 4600 is a lovely monitor. find yourself some daughter cards and get it running is my advice
 
You can find daughtercards for the 4600 on eBay all the time. If you ask in the wanted forum here I bet someone has them as well.
 
Back
Top Bottom