SM124 and huge, black border:

[Muzz73]

I came into an SM124 recently and noticed that the screen is in the middle of the tube and there's a huge border around the outside. It makes the desktop look tiny and seems like an incredible waste of real estate.

 

My old system's SM124 wasn't like this and I don't see any controls on the outside of this monitor for adjusting the screen size.

 

I seem to think that I've heard mention of this before, but I thought I'd see if anyone out there knew of some way I could adjust this thing without having to take a drastic measure of some sort.

 

Thanks in advance!

[Fletch]

My SM124's black border expanded to almost a third of the screen over the years. I very carefully opened the case and in my SM124 there is a series of screen adjustments inside the case. Using a wooden popsicle stick I was able to turn the dials and regain screen real estate.

 

Opening a CRT can be very dangerous. I used the popsicle stick to adjust so I wasn't poking a metal screw driver anywhere near anything that could give me a shock. Apparently some CRTs can hold a deadly charge of electricity for years even when stored unplugged. I recommend being overly cautious.

[Muzz73]

Yes, as I understand it, CRT and the flyback transformer can store upward of 50,000-60,000v even if it's been unplugged for years. Somebody once told me that it's enough to throw you across the room. Yikes!

 

OK, maybe I'll just have to be REALLY careful and use something that doesn't conduct. I remember CRT adjustments from back in the day when I used to work on the old 9" Macs.

 

I was hoping not to have to pull it apart, but you know what they say... "You can't make an omelette without breaking a few eggs!"

 

Thanks!

[fedepede04]

i don't remember how, but there is a way to discharge the power of the high voltage relay.

but i don't think that should be impossible to find on the internet

 

ok stupid me, you need power on, or else you can't adjust the border :D

Edited March 11, 2014 by fedepede04

[Zogging Hell]

Just beware that if you adjust the pots internally to expand the screen it will shorten the life of the monitor. There is a component inside that was only made to work with the smaller screen size and overdriving it will eventually cause it to fail prematurely. There is a fix and you can replace the component with a higher spec one, but it does require something of an operation.

 

You could do it when it was off, but you'd have to make an adjustment then turn on the monitor to check, then turn off again to make more adjustments and so on, although it would probably take a few cycles to get it the right size probably. You would have to leave it off for a bit of time in between cycles to allow it to discharge a bit though. The voltages in an off monitor can produce a very unpleasant shock if not fully discharged (which can damage the monitor anyway if you do it incorrectly), it, apparently from those that have experienced it, is extremely unpleasant but is unlikely to kill you unless you have a heart condition (especially if you use the one hand rule). An powered monitor is a different kettle of fish, is very dangerous, and I wouldn't go anywhere near it unless you know what you are doing. The important thing to remember as well is that is not just the flyback that potentially has a nasty surprise waiting for you, but also the power supply and some of the capacitors. All monitor makes are different as well so there is likely to be a bit of variation in the discharge rate.

[Muzz73]

Hmm... on second thought, I think I'll just live with it. I wouldn't have any idea what to look for in there and like my monitor in working condition!

 

It's not the only monitor I've got, but it's the only high res, paper white display that makes UMS look so nifty...

 

Thanks for the pointers, everyone!

[STuck]

Use a bleed resistor and switch over the caps, then only adjust while it's off. It's still not a guarantee of complete safety though.

[Muzz73]

I don't have any kind of electronics skill to pull that off. That's my problem.

 

I was hoping that it was just a simple adjustment, but it turns out that it really isn't that simple after all. If there's a chance that I'll burn my monitor out, then I'll have to pass on it.

 

Is this something that just happens over time? I only recently got the SM124 and it has a huge border, but when I bought a used SM124 20 years ago, the border was much smaller than the one I have now.

[Zogging Hell]

It won't fail instantly, unless your monitor is really worn out. It might even last years with the adjustment, depending on the current condition of the component. But it will last years less than it would be if you don't do it. Bit of a toss up really. The one monitor I did it on has long since failed, while my other SM124s are still going strong.

 

The dead_mon zip at the link below has the text file which details the problem and fix.

 

http://atari4ever.free.fr/#video