Cannot safely discharge monitor before removing from cabinet

[Pokemon_Steve]

I'm working on my first arcade cabinet and have never dealt with arcade monitors before. I need to remove the monitor to access the speaker compartment above so I can replace the current sound system which is broken. However there is an unremovable back piece of wood that covers the majority of the monitor, only leaving the chassis accessible when the back latch is opened. From all the videos I've watched in regards to monitor safety, it's highly advised to discharge the monitor before doing anything, but I cannot safely reach the anode cap. I was just wondering if I can still attempt to remove the monitor via holding the metal frame and being careful not to touch anything else. The monitor hasn't been powered on in 3 weeks, and prior it had sat dormant for a couple years but I still will assume that it's holding a charge.

Also as a side question, is making a tool of extended length for discharging necessary/helpful for safety purposes? I'm still a little iffy on holding a long flathead screwdriver near the monitor to discharge it even if doing the correct technique (hand in pocket, don't be in contact of any sort of metal, etc.), since I'm not too familiar with dealing with electronics on this level. I had seen a YouTube video recently of a user taping his screwdriver to a wooden rod and discharging his monitor from about a foot away, but that was the only instance I've seen someone do that. If anyone has advice on safety or dealing with being nervous about handling the monitor it'd be appreciated.

- s

 

[piscian18]

So the real danger is between the Flyback and the suction cup on the back of the tube, thats what you're avoiding. I would recommend grounding yourself if you want to be extra careful and wearing some moving gloves so you have a solid grip on the frame when you take it out, but I'll admit Im comfortable enough that I swap tubes all the time without grounding myself..

The goal is to be only touching the front mounts on the tube. If you want honesty, just stay away from touching the back of the tube or the chassis and you'll be fine. It's completely normal to remove a Tube with the chassis and flyback attached. Many cabinets dont even have a rear access. Doing it that way is both for safety and because Chassis are easily damaged.

As for discharging, When I was a nub I literally took a screwdriver and a 4ft Plastic PVC pipe and ducktaped them together like a spear then wrapped a grounding wire around the metal shaft of the screw driver which Id then clip onto the frame. It seems pretty silly in retrospect, but I still have it and now my dumbass is always 3ft away from the tube when Im discharging it.

Technically as long as you have a ground wire touching the metal on the screwdriver and the frame you have little risk of the electricity arcing and hitting your hand.

One real important thing is to try to completely remove the suction cup with your screwdriver if you can without damaging anything. Ive gotten bit by only partially loosening it and going to pull off the cup bare handed, some residual charge still got me.

 

[GeeDee]

You can definitely remove a monitor prior to discharging, though it's good that you're being careful about it. Like you, I always discharge as a step 1 (and as step 2 but still,) the main thing is that discharging should always always always come before disconnecting the chassis from the tube itself, but there are plenty of circumstances where it would be fine to remove the monitor - frame and all - then discharge after it's physically out of the cabinet. Just make sure it's actually unplugged beforehand obviously; there's usually a black and white molex that runs to the iso or something akin to that. In truth, if a monitor hasn't been powered on in a very long time, it has probably lost most if not all of its held charge anyways, but you should always discharge it regardless to keep a good practice. Just some words for comfort.

Also, as far as the discharging tool, you definitely don't need any kind of massive or "official" discharging tool- but to each their own. I just go with the tried-and-true two alligator clips. One to the frame and one to the flathead. I always do the corny thing: tap the anode clips with the flathead a few extra times, then after removing the cup tap the flathead to the anode hole a few times too, etc etc. I wouldn't say having a tool that's overtly longer would really be of any use outside of making you more feel more comfortable. If anything, after you've gone back and discharged the monitor 2/3/4 more times over the course of repairs, you'll probably just end up getting more annoyed at the inconvenience and opt for a shorter flathead anyways

While I don't particularly agree with a lot of the way he handles the anode cap and such, here's one small example: How To Remove A Monitor Chassis Safely - Chattanooga Pinball Company. When they cut to the monitor, it's already removed and on a separate table, but there's a very audible "pop" when he discharges the monitor that you'll almost always hear/see when discharging soon after you've had the tube powered on. At least some proof of concept that discharging after removal isn't a big deal, so long as you're careful about it.

Edit: piscian beat me to it lol- but good advice from them nontheless.

 

[piscian18]

You can definitely remove a monitor prior to discharging, though it's good that you're being careful about it. Like you, I always discharge as a step 1 (and as step 2 but still,) the main thing is that discharging should always always always come before disconnecting the chassis from the tube itself, but there are plenty of circumstances where it would be fine to remove the monitor - frame and all - then discharge after it's physically out of the cabinet. Just make sure it's actually unplugged beforehand obviously; there's usually a black and white molex that runs to the iso or something akin to that. In truth, if a monitor hasn't been powered on in a very long time, it has probably lost most if not all of its held charge anyways, but you should always discharge it regardless to keep a good practice. Just some words for comfort.

Also, as far as the discharging tool, you definitely don't need any kind of massive or "official" discharging tool- but to each their own. I just go with the tried-and-true two alligator clips. One to the frame and one to the flathead. I always do the corny thing: tap the anode clips with the flathead a few extra times, then after removing the cup tap the flathead to the anode hole a few times too, etc etc. I wouldn't say having a tool that's overtly longer would really be of any use outside of making you more feel more comfortable. If anything, after you've gone back and discharged the monitor 2/3/4 more times over the course of repairs, you'll probably just end up getting more annoyed at the inconvenience and opt for a shorter flathead anyways

While I don't particularly agree with a lot of the way he handles the anode cap and such, here's one small example: How To Remove A Monitor Chassis Safely - Chattanooga Pinball Company. When they cut to the monitor, it's already removed and on a separate table, but there's a very audible "pop" when he discharges the monitor that you'll almost always hear/see when discharging soon after you've had the tube powered on. At least some proof of concept that discharging after removal isn't a big deal, so long as you're careful about it.

Edit: piscian beat me to it lol- but good advice from them nontheless.

Id parrot that you need to keep track of the cables going from the chassis to the cab/gameboard. If at all possible disconnect these before you pull out the tube. Easy thing to forget if youve never removed a tube before.

 

[Pokemon_Steve]

Thank you both for your input and advice! I'm glad I can get some assurance that removing the monitor is fine as long as I don't touch any of the back components. Luckily I have 2-3 people available to help me lift it out as well so I won't have any issues with the weight. The tips on discharging are also helpful, I am still quite a scaredy cat so I may opt to attach the screwdriver to something a bit long-ish and non-conductive until I get the hang of the discharging process. When I was very young, I used to have an irrational fear of mouse traps until I started having to set them up myself. I am sure it's the same way for handling these monitors.

Another quick question, if I were to swap pin connectors (switching out game boards that have their own plugs for the video for example) every once in a while, would doing something like that be fine without discharging the monitor?

 

[GeeDee]

That would depend on the game and your monitor in question. Without going into an overly drawn out explanation since there's so many different scenarios, I would tell you to find out if your monitor supports only 15khz games, 24khz (medium res) games, 32 kHz, or any combination of the three. More than likely its just a 15khz only monitor, so most anything that runs on jamma will be fine.

There's also boards like early nintendo games that rely on some funky video inversion and their own audio amp, so depending on what you're trying to play, you may need to do a little case-by-case research

 

[piscian18]

Another quick question, if I were to swap pin connectors (switching out game boards that have their own plugs for the video for example) every once in a while, would doing something like that be fine without discharging the monitor?

Short answer - The only time you ever need to discharge a monitor is if you're removing the flyback to replace or swapping the Chassis. Otherwise leave it alone forever, unpowered Chassis are perfectly safe to work on while connected to a tube as long as you don't put your greasy mitts on the flyback or cup.

Long answer - When it comes to rewiring your video wires for a special circumstance you'd have to handle that on a case by case basis. (in my experience) there are older non-jamma gameboards that may need special wiring. I've honestly never worked on one. Just check your pcb game specs if its predates jamma. Everything I've ever personally used has your typical RGB, Gr, H/V and yeah sometimes you gotta move them around no biggie, just you know..please make sure the power is disconnected when you do it.

 

[Pokemon_Steve]

Good to know, thanks so much. I had a dread that the chassis was kind of an off-limits place to touch in general if the monitor was recently turned on/off but knowing that working with swapping around video connectors is safe to do, I feel a lot better.

I think all of the hardware I plan on using in the future is 15khz compatible since I have a K7400, I did read that plugging anything beyond that can damage the monitor or something... Still really new to all of this in regards to monitors, but luckily there's lots to read up on so I'm doing as much research as I can before I do anything! lol.

 

[Pokemon_Steve]

Back with another question: I know it's recommended for the screwdriver alligator clip to be grounded to the metal frame, but I noticed that my frame is coated ant not bare at all. Are there other places on the monitor I can clip onto for safe discharging? I plan on removing the chassis because after inspecting it, it's definitely in need of cleaning.

 

[Apocalypse]

I would recommend grounding yourself

NOOOO!
I mean that's the opposite you should do (isolate yourself from ground) so the current can't find a way through your body.
When working on high voltage pieces of equipement I need to install a special mat on the floor to be isolated from ground.
Of course the problem when working in a cab is if the frame is made of metal it will provide a path to ground.

[EDIT]
Insulating Matting LV MV HV Switchgear Mats - IEC 61111 Matting (powerandcables.com)

 

[nem]

Back with another question: I know it's recommended for the screwdriver alligator clip to be grounded to the metal frame, but I noticed that my frame is coated ant not bare at all. Are there other places on the monitor I can clip onto for safe discharging?

Personally I place the alligator clip on to the dag wire, the braided metal wire, that is strung from the dog ears and rests on the aquadag coating around the neck.