Metal Disc Under Anode Cap?

D-Roy

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I was in the process of discharging a monitor last night (25" WG, still trying to ID the exact model), and as I slid the end of my discharge tool under the anode cap to make contact with the metal prong part, what looked like a small flat metal disc slipped out and fell into the bottom of the cab. Any idea why that was there or what it could have been for? I thought the only thing under the anode cap was just the metal prong part that attached to the hole in the tube.

From what I saw the split second it fell out from under the cap and into the cab, it was flat like a washer, but without a hole, and was about the size of a nickel. I haven't pulled the monitor yet to get down into the cab to see exactly what it was (Dynamo HS-5).
 
it belongs there.....it sits between the prongs of the anode.
 
Confirmed - I have the same thing on a monitor in a Xenophobe game. You slip it over the tabs for the clip.
 
OK, good to know. Once I manage to find it in bottom of the cabinet and look at it better I'm sure it will make sense. :)
 
You can leave it out. It helps make sure the prongs seat fully in the tube but I, and many others, have been pulling them out for years with no ill effects. Also, I have never seen a replacement flyback with one of these plates in place.
 
The discs help keep dust out of the connection (if any can slip in under the boot), and keep the tension from exceeding the glass break point.

Everything in a design has a purpose. Understanding that purpose means going back to first principles. It's there for a reason - I can't disagree with your observation, but as an Engineer, I try to put things the way the designer designed them.
 
The discs help keep dust out of the connection (if any can slip in under the boot), and keep the tension from exceeding the glass break point.

Everything in a design has a purpose. Understanding that purpose means going back to first principles. It's there for a reason - I can't disagree with your observation, but as an Engineer, I try to put things the way the designer designed them.

I agree with your tension assessment, but I call BS on the dust claim.

Just because the original equipment designer included the tension plate doesn't mean it's necessary for sufficient operation. Personally I feel that those plates are a real PITA and I pull them out whenever I find them.

I've engineered parts before, and I can tell you that more often than not, many of the parts I've included in designs were mainly superfluous - included to appease the concept folks. Not necessary for proper operation, but included for fit and finish, or to ensure that a 90% fit becomes a 99% fit.
 
I've engineered parts before, and I can tell you that more often than not, many of the parts I've included in designs were mainly superfluous - included to appease the concept folks. Not necessary for proper operation, but included for fit and finish, or to ensure that a 90% fit becomes a 99% fit.

What you have provided is accurate. It is possible.

However, how do you know? If you can't answer the question, changes to the design are done at risk, which means:
- Risk of damage
- Increased risk of failure
- Other risks

Here is the bottom line from my perspective: I'm just in the process of finishing a massive root cause on a fire. The main root cause was the design change was inadequate, and it resulted in around a million dollars in damage.

While the stakes are clearly higher in some places more than others (or in an arcade game), unless you know for a fact why something was or wasn't included in the design, you are taking risks in changing it.

I've been involved in designing everything from a simple mechanical system, to a complex digital replacement of an analog system. I understand margins - I add them to every product that I produce as a design engineer. I get very nervous about people assuming why something doesn't need to be included, unless they have it from the person who designed it as to why it was included, and why it no longer is needed.

So, if you are the guy who designed this chassis - I'm good.

Don't mess with the design. It's designed that way for a reason.
 
I didn't take Smalltown's comment as "toss the part", more as a side comment on parts being added due to conceptual concerns, over actual engineering. Point of fact, he didn't say "toss the disc."

That being said, parts may be included in "design" to please a conceptual team, but they were not engineered, unless they also meet function.
 
My guess is it's more about the surface area that the lil disc creates (fit and finish pretty much), basically you can have 2 points of contact or you can have the metal disc contacting all around the anode. Personally when it comes to electricity i prefer the best possible contact.

they can definitely be a bit of a pain but i've swapped my old onto the new when possible.
 
So just to clarify is this piece completely solid or does it have a hole in it like a washer? I fished around the bottom of the cabinet with a magnetic pickup tool and all I pulled out was what looked like a washer.
 
Design Function of the Anode Clip Washer

To put an end to the question of why this device is installed, I contacted my tech rep at Wells Gardner. Per the rep, the Anode Clip Washer has two functions:

1. UL wouldn't certify the monitor without it. I'm fond of UL - they keep things that are bad from happening.
2. The washer is used to mitigate x-ray emmissions in the event the HV exceeds the normal values.

Clearly, 2 is more important than 1.

How often does a HV section go "hot" and high on voltage? I have no information upon which to base an opinion (perhaps some of the guys who work on monitors would). However, given the orientation of various anode points, you could end up x-raying anything from your feet, to the body of the player (on a back to back game).

So, as I have said before, everything has a design function. Until and unless you know what that function is, it's best to put it back the way it was.

Hopefully, this puts an end to the debate.
 
Mitigate X ray damage? Really? If your monitor is emitting x-rays, you've got bigger issues with your chassis to worry about. Plus, there's already circuitry installed that prevents high voltage.

I wonder why manufacturers of replacement flys today don't include them?
 
Perhaps you should ask them.

If they are like the vendors I deal with, you'll be likely to get "we assume that you'll reuse that part."
 
2. The washer is used to mitigate x-ray emmissions in the event the HV exceeds the normal values.

I find this statement interesting as well since X-rays can only be emitted from a CRT where the electron beam strikes the shadow mask or phosphors. This is why they put leaded glass an inch thick as the front envelope. (the part you look at)

Since what you are describing is basically a piece of metal shaped like a round washer and it's inside the anode cup, it couldn't function as a shunt for HV. Since there is nowhere for it to shunt to. Which would be needed to mitigate x-ray emissions.

Typically this is mitigated by part of the HV circuit itself.
 
Both Ken Layton and I remove them and throw them away. If that isn't answer enough...
 
Re: Removing the disks - Awesome. Good luck with that.

My question is why I should bother contacting Wells Gardner or any other vendor to ask them why they do stuff if the general tech's answer is going to be "I don't believe it."

Honestly. It's like saying "don't change a big blue because I've never had one fail."

Disbelief is not an effective defense against the laws of nature and science. You break those laws - and someone's going to pay.
 
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