Hello,
I've bought an Apple II monitor (A2M2010) to replace my Apple III monitor.
When I turn it on it shows image but after 30 secs / 1 min. the screen goes dark. When I turn off the monitor and turn it on again the image shows again for 30 sec / 1 min.
Any idea what could cause this and how to fix it?
Thanks very much,
'nuff
Does the green power LED stay on? If it does then the power regulator is ok and problem likely in horizontal output area
like Q401. Transistors can open as they heat up. Are you comfortable troubleshooting with a voltmeter?
Larry G
Hello Larry,
Thanks for helping out. It seems when the screen goes black the power button light remains green.
To be honest with you I'm not that comfortable using a voltmeter, nor do I have one. I could ask one of my friends or neighbors.
Having said that, when I switched it on to test it didn't even show an image at first. After a few power off / power on I got an image. And now it's been on for over 5 minutes. I'm clueless.
I haven't opened it for a clean, yet. Hope to do that soon.
Thanks again.
Kind regards,
Willem
I'll be 'that guy' and just remind you that there are very high voltages inside CRT monitors, and that death or injury are possible if you don't know what you're doing. It's dangerous, etc etc.
In saying that...
It's not like you can go down to your local Apple dealer and pick up a replacement green phosphor monitor. Even finding a TV repairman is a near impossibility in my area (in general - even more so finding one that would know how to work on a CRT). And if you did find someone, they would probably charge several hundreds of dollars for a simple service.
It's really up to us - Apple II and vintage computing experts - to take a giant leap and start playing with fire, because there is literally no one left that will do it for you. My Monitor II had popped one of its filtering caps after being turned on for the first time in decades, and for the longest time I was resigned to throwing it away. But I kept it, and eventually got the courage to take the cover off and (carefully!) play inside. And I fixed it!
After fixing the cap, it wasn't long before it had another issue with leaking ozone, and this time I had to build up the courage to discharge the tube (something I should have done with my first fix, but didn't). And I eventually got that niggling issue fixed too, with a liberal amount of liquid electrical tape pasted all over the back of the tube and around the suction cup.
TLDR: It pays to be careful with CRT monitors, but they're not made of magic. Despite the warnings, they are entirely repairable by someone with a little electronics experience. Read up on CRT safety and then have a go at fixing it
PS: Don't be stupid like I was by picking up the Monitor II by the handle without screwing it shut again. Watching that tube bounce off my office chair, and somehow not break, was quite a moment for me.
Intermittently working ok or not actually narrows down the possibilities considerably to either a weak startup capacitor or a cracked solder joint (crack in a circuit trace, etc)
Should be easier to fix, not like something shorting out when warms up. Look for a swelled cap, probably a smaller one. Look around with a magnifier glass for cracks.
I serviced CRT monitors for 20+ years.
Larry G
You guys should just be aware that if you discharge the CRT, if the monitor does not have an internal degausser, then you have to buy one and degauss the CRT after you put it back together or the colors will look whacko...
That's interesting, I thought most (all?) monitors degaussed themselves on startup. Does this also apply to monochrome monitors?
It was a moot point for me anyway when working on my Monitor II. I discharged the tube using a screwdriver and grounding wire, but there were no fireworks like I was expecting, not even a tiny crack of electricity, so I'm not sure whether the Monitor II tube is extremely good at discharging itself or if there's relatively low voltages inside a small monochrome monitor like that.
Yes, color monitors have degauss circuits but what he might be referring to is when you lay a CRT on it's face or side it magnetizes because of the earth's magnetic field and sometimes needs several degauss cycles to correct the color. Monochrome monitors do not have this problem or degausser. High voltage on a monochrome tube is usually < 10KV. Color tubes are > 20KV. Rule of thumb is HV arcs about an inch for each 10KV. I did CRT service for over 20 years. I've drawn a 2 to 3 inch arc off a color CRT anode while it's running.
Larry G
Okay... I would never ever want to discharge a monitor while it's turned on, but good to know!
Rule of thumb is useful as well.