Capacitor for a power supply

shred

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I am rebuilding a power supply for a cosmic avenger and just wanted to make sure I got the right type of capacitors. On mouser it came up with so many different types.

CAPACITOR 35V 68OOUF 105C HIGH TEMP, 105C, RADIAL
CAPACITOR 16V 10000UF 105C HIGH TEMP, 105C, RADIAL

Thanks
Dave
 
Last edited:
The "right" one

To be honest, unless someone has a manual, we can't tell.

Can you take a picture of the one you currently have, or at least post the markings?

Generally, you should try to get one that is the same shape, size (as close as possible) and greater than or equal to the voltage rating, with the same capacitance.

Size does matter. The formula for capacitance is 0.225 x K x A / S where
K is the dielectric constant
A is the Area of the plates and
S is the Space between the plates.

For filter capacitors, these constants do matter, which is why you need a capacitor that is a close match so you get similar results.

So, post some information, and I'm sure someone will jump in with the right capacitor.
 
To be honest, unless someone has a manual, we can't tell.

Can you take a picture of the one you currently have, or at least post the markings?

Generally, you should try to get one that is the same shape, size (as close as possible) and greater than or equal to the voltage rating, with the same capacitance.

Size does matter. The formula for capacitance is 0.225 x K x A / S where
K is the dielectric constant
A is the Area of the plates and
S is the Space between the plates.

For filter capacitors, these constants do matter, which is why you need a capacitor that is a close match so you get similar results.

So, post some information, and I'm sure someone will jump in with the right capacitor.

Those values are correct. I need 3 of each, I got them off the schematics. (3) 35V 68OOUF (3) 16V 10000UF


I was just wondering mainly the type of capacitor thats best for this power supply. Should it be high temp? low emf or does it really matter?

Dave
 
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High temp - 105c is what you need.

No need to spend the extra money on low EMF caps. Those are generally used on computer motherboards in the low voltage regulator section.

You do need to make sure to get the proper mounting type of capacitor: radial (both leads come out of the same end of the cap) or axial (one lead comes out of each end of the cap.) The axial types can be hard to find.

RJ
 
High temp - 105c is what you need.

No need to spend the extra money on low EMF caps. Those are generally used on computer motherboards in the low voltage regulator section.

You do need to make sure to get the proper mounting type of capacitor: radial (both leads come out of the same end of the cap) or axial (one lead comes out of each end of the cap.) The axial types can be hard to find.

RJ

That is what I figured.. I have not done any repairs in a while so I wanted to verify everything. Trying to get back into the swing of things and don't want to make any mistakes. Amazing how much you forget if you don't keep up on things. Thank you very much.

Oh by the way I sent you a request on fixing a crazy climber board set. Never got a reply on if you would want to. Maybe lost email.

Dave
 
I'm way behind on emails on the site and I spent last week in the US Virgin Islands with my son which put me further behind.
 
Yup!

Vacation on the cheap... 239,400 airline miles paid for the flights, rental car, and hotel.

We had a blast!

:D
 
Believe it or not (and Test it yourself)

The size and shape of capacitors DOES make a difference. All microfarads are not "the same."

Example: GE Feedwater Control system DC power supply. Maximum ripple allowance: 50 mv.

We obtained new capacitors that were the same voltage and capacitance rating, brand new manufacture. The caps were installed, and the ripple was out of tolerance. The shop got out another brand new set, installed them, and had the same results. They even pulled out the capacitance tester, and verified the capacitors had the right rating, and were not shorted.

Engineering was called in to support the maintenance issue.

Going to first principles, we started by comparing the new capacitors to the old capacitors, and found the old ones were taller and wider. The new ones were shorter and skinnier.

We did a back of the envelope calculation of the capacitors (nobody wanted us to take apart the capacitors and how would we be able to tell what the electrolyte constant was anyway), but we showed that the smaller, skinnier caps would have to have a different internal structure. We postulated that the difference was causing higher ripple (AC leakage).

We went to Mainline Electronics (now out of business, formerly located in Plainfield, IL) and asked them if they stocked NOS capacitors that matched the voltage, capacitance, and approximately the size.

They did (they even had the original manufacturer!) We installed the NOS capacitors, and the ripple dropped to well within tolerance.

So, lets look at the "why" of this.

Again, capacitance is derived from the formula 0.225 x K x A / S, where:

0.225 is an eigenvalue
K is the Dielectric Constant
A is the Area of the Plates
S is the Space between the plates.

By using a different dielectric, I can reduce the area of the plates and the space between the plates.

Example:
K = 4
A = 11 sq inches
S = 0.1 inch

= 99 mF

Now tweak the dielectric constant:
K = 7
A = 6.3 (reduced area, less paper, cheaper to produce)
S = 0.1 inch

= 99.25 mF

So for filter caps, Size Does Matter. For your run of the mill caps, it may not. It's also why when you get a filter cap from The Real Bob Roberts, it looks like the old cap you removed, not a new svelte one.

By the way, the original New Capacitors were provided by GE Nuclear, which has a Nuclear Quality Assurance program governed by 10CFR50 Appendix B. The capacitors provided by GE had the right capacitance - it just didn't work in the filter circuit.

Believe it or not. Try it yourself on a power supply. Not all capacitors are equal, even if they have the same rating.
 
The size and shape of capacitors DOES make a difference. All microfarads are not "the same."

Example: GE Feedwater Control system DC power supply. Maximum ripple allowance: 50 mv.

We obtained new capacitors that were the same voltage and capacitance rating, brand new manufacture. The caps were installed, and the ripple was out of tolerance. The shop got out another brand new set, installed them, and had the same results. They even pulled out the capacitance tester, and verified the capacitors had the right rating, and were not shorted.

Engineering was called in to support the maintenance issue.

Going to first principles, we started by comparing the new capacitors to the old capacitors, and found the old ones were taller and wider. The new ones were shorter and skinnier.

We did a back of the envelope calculation of the capacitors (nobody wanted us to take apart the capacitors and how would we be able to tell what the electrolyte constant was anyway), but we showed that the smaller, skinnier caps would have to have a different internal structure. We postulated that the difference was causing higher ripple (AC leakage).

We went to Mainline Electronics (now out of business, formerly located in Plainfield, IL) and asked them if they stocked NOS capacitors that matched the voltage, capacitance, and approximately the size.

They did (they even had the original manufacturer!) We installed the NOS capacitors, and the ripple dropped to well within tolerance.

So, lets look at the "why" of this.

Again, capacitance is derived from the formula 0.225 x K x A / S, where:

0.225 is an eigenvalue
K is the Dielectric Constant
A is the Area of the Plates
S is the Space between the plates.

By using a different dielectric, I can reduce the area of the plates and the space between the plates.

Example:
K = 4
A = 11 sq inches
S = 0.1 inch

= 99 mF

Now tweak the dielectric constant:
K = 7
A = 6.3 (reduced area, less paper, cheaper to produce)
S = 0.1 inch

= 99.25 mF

So for filter caps, Size Does Matter. For your run of the mill caps, it may not. It's also why when you get a filter cap from The Real Bob Roberts, it looks like the old cap you removed, not a new svelte one.

By the way, the original New Capacitors were provided by GE Nuclear, which has a Nuclear Quality Assurance program governed by 10CFR50 Appendix B. The capacitors provided by GE had the right capacitance - it just didn't work in the filter circuit.

Believe it or not. Try it yourself on a power supply. Not all capacitors are equal, even if they have the same rating.

Ouch!....brain hurts;).
In all seriousness, I totally agree with you.......but these old video games just arn't that picky. They can tolerate quite a bit of AC ripple before they go bonkers (but....the less AC ripple, the better).

You're gonna start a wave of noobies comparing all their cap sizes, and flooding questions......"Is this cap too small?":eek:

Edward
 
I am not exactly a newbie and I know you meant other people too.
I have been in this hobby for a really long time. I have repaired monitors and power supplies before. I am by no means a electronics expert though, I can do some basic trouble shooting and repair. I just have been laying low the last 3 years or so when the economy took a dump and so did my job. This hobby is expensive so I shelved all my projects. I didn't sell or get rid of any of my games or projects.

It does amaze me how much you can forget though in 3 or 4 years of not doing something. I always like to ask those more knowledgeable than me though when it comes to power supplies because occasionally they do require a special cap or a special part. I would hate to fry some boards.

Anyway I do really appreciate the help everyone.

And Edward I do understand what your saying, you have been a big help in this hobby for a long time.

channelmanic good you had a great time. Did you snorkel or do any scuba?

Dave
 
I hope you don't think I was calling you a noobie....I wasn't. I was really generalizing.....and trying to be a bit funny!:)

Edward
 
I hope you don't think I was calling you a noobie....I wasn't. I was really generalizing.....and trying to be a bit funny!:)

Edward


No I get what you were saying.
I just kind of asked a newbie question. I don't care though because I do not want to screw up. I was just explaining why and what happened to me for a while.

Dave
 
We did snorkel, snuba (like scuba but 20' max depth and the tanks are on a raft...), jet ski, and the moonlight bio-luminescent kayak tour.
 
The size and shape of capacitors DOES make a difference. All microfarads are not "the same."

Example: ....

Putting on my best Dr McCoy voice...
"My, gawd Jim! This is a simple linear power supply...not a nuclear ractor controller!"

For a linear such as this, the original caps were simply %80/-20% common off-the-shelf caps. Just go for the same size and voltage (or a little higher in voltage). And if the post office saying applies (if it fits, it ships) then you're good.

Incidently, I have brand new Panasonics for the 10000uF, 16V cap available here:
http://www.greatplainselectronics.com/Category-66.asp
Panasonic ECA-1CHG103 -- less than 1/4 the price that Mouser wants.

Can't help with the 6800, though.

Ed
 
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