How do you test big Blue?

A good quality analog ohm meter can check it on the R X 100 scale.

If you have a good quality digital capacitance meter you can read the capacitance of it directly.

You can also substitute a known good (or brand new) capacitor of the same value.
 
Thanks for the post Ken.

I have a blue esr meter http://www.anatekcorp.com/blueesr.htm

Specifications:

Measurement range: 0.01 to 99 ohms, auto-ranging
Peak voltage across capacitor under test @ full scale: 100mV

I was hoping that might handle the big blue but you did not mention an esr.

My mm is a very cheap one. One of those red three dollar cen-techs from harbor freight...

Last but not least is a tek scope but I wouldn't know how to set it up with out any help.

Could an esr or a scope check out the big blue?
 
Could an esr or a scope check out the big blue?

I would think you could test the cap with a scope. The "big blue" smoothes out the ripple in the circuit. Without load even a pretty bad cap will smooth out the ripple. Under full load is where the cap is tested. I say load the 5v circuit to the max (not sure how may amps that would be) and see how clean the 10.3v unregulated and 5v regulated lines are with the scope. Compare it to a brick with a new "big blue". Maybe someone has a digital scope and can capture a known good signal and post it for us.
 
I'll add my two cents.....I test big blues with my meter on AC volts. Ultimately, that's what we're looking for....excess AC on the DC rail. Now, how much AC is too much?

Measure the 10 volt DC test lug on the A/R II board, but have your meter set to AC instead of DC. From my experience....Anything over .5VAC is bad news. I've never had an Atari game run with that much AC. If the voltage is bouncing around, that's bad news. Now, if your in the .3 range, it's questionable.....but big blue is on it's way out. I've had some games work fine at .3VAC.....others won't. As already stated, I've had some work up to almost .5VAC. Every game is different.

Also of note....some meters (especially cheap ones) can't read AC on a DC rail. they get "confused". If you get something like 15VAC.....your meter's confused. As others have stated, you can use your scope for this. It won't have a problem reading AC on the DC rail.

Edward
 
Most of the time when I've had a bad "big blue", it has gone open circuit. That can be found with an ohm meter.

Most ESR meters will not read a capacitor with this large of value. ESR meters are generally intended for electrolytics of 3000 uf and smaller.
 
Most of the time when I've had a bad "big blue", it has gone open circuit. That can be found with an ohm meter.
Hey Ken, I'm missing something here. I thought any cap that wasn't shorted would test as open on an ohmmeter?
 
Anybody know where the test points for testing a Big Blue on a Q*Bert would be? I've mostly read about testing them at the audio boards on Atari games.

PXL_20220304_013149953.md.jpg
 
Clip your meter onto the resistor leads. You need everything plugged in to do it!

Measure VDC and VAC both like I said in the other thread.
 
You win Necromancer thread of the day ! Congrats ! 12 years. I did one 10 years old, 2 days ago. You beat me with this one.

That said, I was confused.. so I'm looking for a "Big Blue" (Street Fighter) cab. I was like... how the f do you test a cab ? Now I guess I just learned "Big Blue" can also be a huge ass cap ? Dang man, we gotta get more unique for these nicknames.. sh*ts confusing.

That is awfully big and blue though !
 
Last edited:
You win Necromancer thread of the day ! Congrats ! 12 years. I did one 10 years ago 2 days ago. You beat me with this one.

That said, I was confused.. so I'm looking for a "Big Blue" (Street Fighter) cab. I was like... how the f do you test a cab ? Now I guess I just learned "Big Blue" can also be a huge ass cap ? Dang man, we gotta get more unique for these nicknames.. sh*ts confusing.

That is awfully big and blue though !
it's a filter cap. Big Blue is just some thing Bob Roberts marketed it as, which is a little strange given the replacements aren't even blue, they're black.

Randy Fromm made an instructional video from probably about 1982 about linear power supplies and it was truly enlightening.
 
it's a filter cap. Big Blue is just some thing Bob Roberts marketed it as, which is a little strange given the replacements aren't even blue, they're black.

Randy Fromm made an instructional video from probably about 1982 about linear power supplies and it was truly enlightening.
So now-a-days they are "big blacks" ? lol (BTW-Don't google that... unless you like porn.)

Yea I watch a monitor instructional video a lot by Randy Fromm. I haven't got through it in one sitting yet, but I have watched all of it now over time. The dude is great. Explains things very well. Also - WOW CRT's are like some old futuristic technology of insanity. Now that I understand a little about how they work, I am surprised they work at all !! haha Its amazing, really.
 
Back
Top Bottom