Atari Big Blue Cap: what is used for?

baritonomarc

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Hi all,

i am trying to face a problem on the Disco monitor my Paperboy is equipped with, and i suspect (i hope, really) the culript is the big blue.

So, the question is: what is the big blue used for? Could it be the cause of a high ripple that can cause a malfunction of the monitor or is it used in the power section of the game board only?

Thanks!
 
Hi all,

i am trying to face a problem on the Disco monitor my Paperboy is equipped with, and i suspect (i hope, really) the culript is the big blue.

So, the question is: what is the big blue used for? Could it be the cause of a high ripple that can cause a malfunction of the monitor or is it used in the power section of the game board only?

Thanks!

Yes, it can cause monitor problems

From here
http://arcadecontrols.com/BBBB/bigblue.html

* 1 Intermittent lightning streaks in pic/hum bars/weaving.
* 2 Blank raster... steady or intermittent.
* 3 Jumpy pic sometimes described as jiggles.
* 4 Failure of H hold to lock in.
* 5 Intermittent vertical roll or failure to lock in.
 
It filters the DC Ripple

un-filtered.jpg

The bottom wave (Above) is almost like AC, so the big blue capacitor fills them in to make it cleaner and more like a battery

Like this
filtered.jpg
 
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Still have to find my first defective Big Blue.

I bought a ESR meter and recently tested an old Big Blue (UK made, from an Irish cab) and it was showing better results than a new one from BR.

Not saying they never die of course....but I'd re-cap my monitor first.

It looks like the smaller the caps, the sooner they are bad.
 
Still have to find my first defective Big Blue.

I bought a ESR meter and recently tested an old Big Blue (UK made, from an Irish cab) and it was showing better results than a new one from BR.

Not saying they never die of course....but I'd re-cap my monitor first.

It looks like the smaller the caps, the sooner they are bad.

Yep, I've seen 4 or 5 bad ones in my time.....and I've been inside hundreds of games. Do they go bad....yes. Is it as common as people think....no!

To the OP.......big blue takes in a 36 volt AC tap from the transformer. Big blue and the bridge rectifier convert this AC line into a DC line (well, the bridge does the "converting" while big blue (attempts to) remove "leftover" AC. When this process is done, you're left with approximately 10-14 volts DC unregulated. This voltage now enters the Audio/Regulator board.....and gets regulated down to 5 volts DC. This is the 5VDC that powers the game board.

Edward
 
You can easily tell if the cap is bad, by measuring the AC voltage ripple on the DC output.

If you read alot of AC voltage say .5 VAC or more then replace it.
 
A "big blue" cap could not possibly cause an actual monitor problem. It filters the rectified 10.6VDC from the transformer block, which goes to the AR and is used to audio amplification and regulated to +5VDC. AC power for the monitor splits off well before "big blue" comes into the picture.

I believe what Bob Roberts meant to say is that it can cause symptoms that mimic, or appear to be, monitor-related. The problems he lists must have been caused by a PCB getting too much ripple on its 5VDC line (due to a bad big blue); yet they might _appear_ to be monitor problems.

Easy way to perform differential diagnosis: try the monitor with another game (powered by an other power supply). If it works fine, you have an issue with the Paperboy. If it still manfunctions, you've got an issue with the monitor.
 
Just check a couple of hours ago (i was too curious to see "what lies undeneath that block of blue caps and metal" :D) and the line going to the monitor is AC and do not go trough the big blues (i have two of those beasts in my paperboy).

i have a monitor issue then...

thank you all for the kind, fast and exaustive help (see ya on dragonslairfans Level42 ;))
 
I tested everything in my PB when it was overheating and came up with nothing but good readings (or so I thought) for those big blue caps. I finally gave in and replaced them and the game worked just fine after that. If you think they may be defective, save yourself some time and swap em.
 
Still have to find my first defective Big Blue.

I bought a ESR meter and recently tested an old Big Blue (UK made, from an Irish cab) and it was showing better results than a new one from BR.

Not saying they never die of course....but I'd re-cap my monitor first.

It looks like the smaller the caps, the sooner they are bad.


My thoughts excactly! Big caps don't often die, if they are left for a long time without power they can go a bit strange and need reforming.
 
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