X-Ray Protection Caps

Hyde

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Alright, a post that someone made here on these forums has gotten me pretty paranoid.

Apparently, some operators used to clip off the x-ray protection capacitors on monitors to get them to work. This, however, exposes the player to harmful x-rays.

Is this really true? And how can I tell if the X-ray protection caps have been taken out of my games? I'd really hate to be exposing myself to harmful radiation just to play a couple games of Frogger.
 
I saw that post and wondered about it too. However, CRT screens are made from heavily leaded glass, and I always assumed that that was all the protection from harmful rays you need.
 
I saw that post and wondered about it too. However, CRT screens are made from heavily leaded glass, and I always assumed that that was all the protection from harmful rays you need.


So the rays come from the front , not the back where the tube is ?
 
Some ops with do anything to get a game going again cheaply. Will someone please chime in with some info?
 
An informal history of X-ray protection

(The following is from: Marty).

Most of the old tube type color TV sets used a shunt HV regulator tube, usually a 6BK4. If it failed, or some component in the HV circuit failed, the high voltage, normally 25kV, could go up to 35kV or more, causing some X-Ray leakage from the CRT. In the early 70s when news of this radiation scare was first announced, there was a public outcry to immediately fix the problem. The feds hastily imposed a requirement on manufacturers of TV sets to somehow render a TV set "unwatchable" if the HV exceeded rated limits.
The manufacturers first response was to follow the letter of the law and the first "HEW" circuit simply blanked the video when the HV exceeded a setpoint to make the set "unwatchable".
It was quickly noticed that the HV was not turned off with this circuit and the CRT still could emit some radiation. Many TV sets with this feature were left on so the consumer could listen to the sound, so the feds tightened the requirement.
By this time new TV sets were all solid state and some manufacturers experimented with HV shutdown circuits, but most of these circuits were poorly designed and not reliable.
Zenith thought they had the answer by regulating the HV with a bank of 5 capacitors across the horizontal output transistor to "hold down" the HV to 25kV. If one capacitor opened, the HV would only rise about 2kV, not a dangerous situation. This wasn't good enough for the feds.
The "fix" that Zenith finally came out with, was a "4 legged capacitor". Two legs were the emitter return for the horizontal output transistor, & two legs were the HV holddown capacitor (the equivalent value of the bank of 5 caps). This "fix" was accepted by HEW and millions of TVs were produced. It worked so well, that other manufacturers soon followed the lead (Magnavox, GE, etc.).
Then the worst happened! The 4 legged monsters started failing in a large numbers. Not opening completely & not shorting out. They sometimes allowed the HV to skyrocket to over 50kV. Some of them even cut the necks off of the CRTs.
Zenith issued a recall on those models with the problem (more than one entire model year). After several "improved" versions of the capacitor, the problem was fixed but that recall almost bankrupted the company. Other companies had failures too, but usually not as dramatic as Zenith's.
Magnavox used the HV holddown capacitor, both single & 4 leg version in several 70s era TV sets and is a good candidate for fireworks as well.
(From: Roy J. Tellason ([email protected]).) The problem was reputedly due to a capacitor maker substituting a different (cheaper) material for the one that Zenith originally specified, leading to the failures. I can't recall who the cap maker was (some company in Taiwan?) but remember hearing as to how they were the ones who ended up having to pay for all those warranty repairs, including CRT replacements.
 
That was actually a pretty good read. So are most monitors past 1980 or so relatively safe? I'm still a bit nervous about the operators removing the caps, though.
 
That was actually a pretty good read. So are most monitors past 1980 or so relatively safe? I'm still a bit nervous about the operators removing the caps, though.

No arcade monitors (that I'm aware of) solely use caps for their HV shutdown. The high voltage shut-down is a circuit...made up of a handful of componets....it differs from manufacturer to manufacturer...transistors, diodes, IC chips, etc.

Edward
 
No arcade monitors (that I'm aware of) solely use caps for their HV shutdown. The high voltage shut-down is a circuit...made up of a handful of componets....it differs from manufacturer to manufacturer...transistors, diodes, IC chips, etc.

Edward

On my G07-FBO it was a transistor I had to remove... I don't remember which one though, I still have the transistor laying around on the counter, I just need to recap the monitor and see if that brings everything back to where it should be.

All that did, from everything I've read, is disable the protection circuit and allow the monitor to run as a "mobile hot zone"...

Again, that's from what I read... I don't have a Geiger counter... so I just have to take "they're" word for it.
 
From what everyone has said, if you have an HV probe, you can just make sure your outputting the right HV. ;)
 
I have a Berzerk machine with a G07 in it, and one day had 3 glowing balls of color in the middle of the screen. I was also getting no HV.

I then desoldered the x-ray protection transistor (x701), and got a VERY bright picture, that could not be adjusted down much. I checked the HV and it was around 35,000 volts (too high). When I put the transistor back, there were the 3 glowing balls again, and no HV.

So, the voltage regulator transistor on is probably bad.

But, the picture looked TERRIBLE with that kind of voltage and disabled x-ray proteciton.
 
My aunt would always tell me to get back from the TV,so I wouldn't get Radiation. I always thought that she was just plain crazy. At least she wasn't completely crazy.

Of course, she would go nuts if you ran a TV and a radio at once... Because you are wasting electricity. But really she has a point. Over exposure of media is a pretty bad thing.
 
Chad has no idea what he's talking about :) The radation he absorbed was from the Hulu Aliens turning his brain to mush. But I think for the most part the X-rays go out the back of the tube correct? But as stated before, if you HV goes above say 25kV your picture will look like crap.

If you are still scared, put your lead undies on :)
 
Alright, so I feel a bit better now. So basically, if the voltage is too high then the picture will look like crap?
 
Chad has no idea what he's talking about :) The radation he absorbed was from the Hulu Aliens turning his brain to mush. But I think for the most part the X-rays go out the back of the tube correct? But as stated before, if you HV goes above say 25kV your picture will look like crap.

If you are still scared, put your lead undies on :)

Anyone have a picture of what the crappy screen looks like ?
 
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