Rookie Mistake

[TheMacGuy]

I got the 128k board in today, and I went to test it in the 512k. Standard procedure:

Unscrew handle screws, Battery compartment screw, two screws above the ports. Unplugged the floppy drive. Then I went to unplug the main connector. It was stuck in the connector for whatever reason. So I reached in further, grabbed the connector and pulled.

SMACK. My hand hit the neck of the CRT. It has been unplugged for weeks so I didn't get shocked (do the necks even hold that much voltage?). Looked like nothing was wrong, but upon closer inspection:



Can I just push it back down or will I have to replace the whole CRT?

 

[Trash80toHP_Mini]

Pull it off to inspect the pins and the vacuum containment teat for damage. If you haven't let out the vacuum (an event you would likely have noticed) and just the pins are bent a bit, just shove 'er back on and fire it up. It's the anode under the suction cup that's the shock hazard. The tube itself retains a charge that can attack you from under there.

 

[Brooklyn]

That's a connector, not a soldered joint, so it is designed to be unplugged. So push it back down and you're fine.

UNLESS you broke the neck glass at the tip. I did this once...I heard a hissing sound as air entered the tube, and it left a mark on the front phosphor. I ended up replacing the whole CRT but it ended up being easier than I thought.

 

[uniserver]

containment teat

LOL



Yep all it takes is that little teat to break and the atmosphere rushes in contaminating the guts.

 

[James1095]

You'll know right away if you break the tube. It will make a sickening *tink*PSSSSSSSSSSSSSSSSSSSSSssssssssssssssssssssssss as your heart sinks knowing that tube is destroyed. The glass exhaust pip is fragile so you do have to be careful unplugging that connector. Once air has got in the tube, it's a goner. It could be rebuilt, but to my knowledge there is only one remaining CRT rebuilder in the world, RACS in France and obviously that is not cost effective for a tube like this.

There is actually very little shock hazard working with these small tubes. The high voltage is at the second anode, the connection under the suction cup looking thing. If you plan to work around the tube, it is a good idea to discharge this, but if you are expecting a big flash and bang you will be disappointed. Connect a wire to the bare ground wire sprung around the bell of the tube and poke the bare end under the suction cup. If there is any charge left, you may get a small spark like static electricity on a dry day. I usually clip an alligator clip between the anode connection and ground to keep it discharged, sometimes a bit of static can build back up from inside the tube. It won't kill you but it could startle you enough to drop the tube on the floor.

 

[volvo242gt]

And, at that point, you'll hear not only the *tink*PSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS, but a *crash*.

-J

 

[TheMacGuy]

Thanks for the help guys!

Thankfully, I didn't hear the "*tink*PSSSSSSSSSSSSSSSSSSSSSssssssssssssssssssssssss", so I think the tube is fine. I just gotta be more careful and remember that my big hands don't fit into tight places.

I should have some free time on Sunday to take a look at it. I'm going to wait until I can see if anything broke before looking for a replacement. I have a nasty habit of thinking I need a part, finding what I think is a good price for it, ordering it, turns out I don't need it and holding onto it indefinite amount of time.

I ended up not getting to test the 128k board, but I have no doubt in my mind after inspecting the board that it is a 128k. I will talk about it more in the Conquest forum.

 

[TheMacGuy]

I'm going to get Mac-crackin' after dinner today. Anything I should make sure of while in there? Any special tasks I should preform before pulling off the board? If any pins need to be straightened, should I just use a flat-head screwdriver? Or just push the board back on if the glass tube didn't crack?

 

[James1095]

Just push the board back on, it looks fine. If you do come across bent pins on a CRT, straighten them out with your fingernail, they're quite soft. If they're bent badly, try some small needle nose pliers but be careful not to apply force too near the glass to metal seal.

 

[TheMacGuy]

The board actually just went straight back into its spot. Booted it up, and it worked like a champ.

 

[techknight]

I still wont forget the time that I fixed a CRT monitor that had a bad HOT. It had a nice bright crisp, sharp and clear picture. Better than any other CRT I had at the time. So, I was going to swap it out with the trinitron I was using at the time.

I sat the monitor on the couch tube face down, and before I could turn around to grab the one off the desk, dog jumped up on the couch. I heard the infamous Wack. PSSSSSSSSSSSSSSSSSSSSSSSSSSt. FUUUCK me. Monitor flipped off the cushion and hit the floor. broke the CRT neck.

That sucked.

 

[James1095]

It happens. I once did a similar move as the OP here and whacked my hand against the neck board of a monochrome VGA monitor, cracking off the pip while trying to unplug something. Several years later I was working on a nice 15" SVGA back when that was considered quite a nice monitor and I left something unplugged, causing the beam to not blank instantly when I shut the monitor off and it instantly burned a little dot into the center of the tube. Several years after that I knocked something over in the garage and it fell just perfectly and smashed the neck off an arcade game monitor that I was repairing for someone else. Doh! That one was in great shape with no burn either CRTs are fragile. At least the larger ones usually have a protective cap over the exhaust pip.

 

[uniserver]

What's even more fun is when you turn a tube on after that broke.

it was a nice smoke and light show

my FDHD, had one of those red aluminum, after market hard drive mount trays.

it came apart in shipment, smacked the tube / broke the pip.