What do Bally/Midway MCR power supply Caps do

edelgiud

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Hi. I am trying to clean up a Spy Hunter and some extra parted machine parts.

What are the two big caps that are in the linear power supply block used for?:
Midway (MCR) Capacitor 55,000uf 25v
Midway (MCR) Capacitor 100,000uf 16v

How do I go about testing them to see how good they might still be after 25 years? Or what symptoms happen when they go bad?

Should I just check if Bob Roberts still has some for sale?

I would like to learn what to test if you care to share your knowledge. Thanks.
 
Hi. I am trying to clean up a Spy Hunter and some extra parted machine parts.

What are the two big caps that are in the linear power supply block used for?:
Midway (MCR) Capacitor 55,000uf 25v
Midway (MCR) Capacitor 100,000uf 16v

How do I go about testing them to see how good they might still be after 25 years? Or what symptoms happen when they go bad?

Should I just check if Bob Roberts still has some for sale?

I would like to learn what to test if you care to share your knowledge. Thanks.

They smooth out the the unregulated 5vdc and 15vdc that then goes to the power supply board. When they go bad sometimes a little AC "ripple" voltage creeps through. Test for AC voltage on the block connector 1 pin 6 red wire(15vdc) and pin 4 or 8 black wire(5vdc) to see if you get any noticeable AC readings. You shouldn't get any. If you are using a switcher instead of the original power supply they are not used and can be ignored. If you plan to use the original power supply than I would highly recommend replacing these caps if they are original.
 
They smooth out the the unregulated 5vdc and 15vdc that then goes to the power supply board. When they go bad sometimes a little AC "ripple" voltage creeps through. Test for AC voltage on the block connector 1 pin 6 red wire(15vdc) and pin 4 or 8 black wire(5vdc) to see if you get any noticeable AC readings. You shouldn't get any. If you are using a switcher instead of the original power supply they are not used and can be ignored. If you plan to use the original power supply than I would highly recommend replacing these caps if they are original.

Thanks! Does the load (power supply board) have to be connected to these points?
 
Not for testing for AC ripple. But for an accurate test of the proper DC +5voltage it should be tested on the sound board.
 
Hi. I got back to this project. I had two supplies. One had the 55000mfd cap that was bad. For the others, the AC ripple measures .08 VAC. Is that acceptable? Tx.
 
Also, what does the 35MFD (correction 3.5MFD) 440VAC metal capacitor (that is linked to the transformer for the 8-10V side I believe) actually needed for? Can these go bad (can they be tested)? Thanks.
 

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on a spy hunter if those caps go bad there are a few things I've seen. I've seen the board not power up at all. I've seen the game play fine visually but have a really really bad hum in the audio. I've seen a wave in the monitor due to these being bad. I've seen the game boot to junk because those were bad. Most people overlook and down play those caps but on a spy hunter they are sort of a big deal IMO. I consider replacing them standard maintenance for a spy hunter that you want to run reliably.
 
Also, what does the 35MFD 440VAC metal capacitor (that is linked to the transformer for the 8-10V side I believe) actually needed for? Can these go bad (can they be tested)? Thanks.

If you replace this.....I don't think it's a 35MFD........maybe 3.5MFD?

Edward
 
If you replace this.....I don't think it's a 35MFD........maybe 3.5MFD?

Edward

Yes, correct, thank you! Here is the schematic portion in enclosed pic (left, bottom). I know that everybody changes the Big Electrolytic caps but those this cause any problem/go bad, etc.?
 

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I've seen that oil cap go bad a few times....though, not as much as the electrolytics. Both times I've replaced it, it was causing a bad hum bar.


Edward
 
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