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Gb: Rectifier boards

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Found'em.

Thanks for not spoon feeding me........again.
I do appreciate the tip on the caps being film. You were RIGHT!

Metalized Polyester Radial Lead Capacitors made by CDE.
Non polarized, non inductively wound. :) Perfect for this.

I just needed a hint on where to look.

I love this group of folks, very knowledgeable and helpful, always willing to share their experience.


Cviller, better learn to eat with chopsticks.

Ron
 
This is really a Norcal thread (cviller, I'm just on the other side of the hill from you)! Maybe we'll get to meet at BA.

cviller said:
Cool article - I just skimmed it briefly, but it seems like he is looking at a single diode (half wave). He tries to justify that his calculations holds for full wave rectifiers too and he is probably right. :D

Good point. I never noticed that. He does discuss (at the bottom of page 7) comparison with a full-bridge rectifier, and I think he would say you only need the snubber RC across the whole bridge. I guess that the characteristics of each of the four (or two or however many) diodes and of the transformer are the same, so perhaps snubbing across all of them should be as effective as across each one. Of course, it would seem that snubbing across each diode would also be fine.

Renron said:
Thank you for taking the time to answer my (probably) foolish question.

I found some other stuff too, a 100V poly cap from Panasonic which, after I looked up the specs. led me to a table of "Permissible Voltage (RMS) in Alternating Current Corresponding to DC Rated Voltage". This particular unit I have is rated for 63V RMS Alternating Current. :) I had no idea capacitors other than nonpolarized could be used safely in SOME A/C applications.
[/B]

Not foolish questions. Trust me - I do not know much myself. I don't understand your statement about polarized caps in AC circuits. You CAN use polarized capacitors to block direct current, such as in the input of a preamp, allowing alternating current to pass. However, off the top of my head I can't think of a power supply scenario where you would be able to use polarized capacitors with AC. From the table title, it sounds to me that it's referring to some de-rating of voltage when a NONPOLAR (your poly cap is nonpolar) cap is used with AC. The specified voltage rating is probably for DC.

Renron said:
As long as I am pickin' yer brains......
What does the P mean?
I presume this is a film cap. yes?

Definitely is a film cap. I'm not sure what the P means. The K is a tolerance mark. Perhaps the P is a manufacturer marking for the type of film used?

cviller, sorry about all of the off-topic here.
:ashamed:
 
Heatsinks

Hey Christian,
I was thinking of using TO-247 rectifiers on your boards. You gave a reference for a heatsink in your first post.

2 questions:

1. Will the heatsinks that you referenced accept a TO-247 device?

and

2. On the same datasheet as the sinks you referenced I found some that seem speced for TO-247's (the 657 series). Are these sinks -- http://www.mouser.com/ProductDetail/Wakefield/657-20ABP/?qs=sGAEpiMZZMuFYi0ZsYM5P2w8Sx8qfhz0 -- too wide for your boards? Or, will they fit ok?

Thanks,
Steve
 
The snubbers (caps and resistors) are inserted to filter out switching noise from the rectifiers, so this has nothing to do with what you are using the bridge for - with correctly matched snubbers (matched to diodes) you'll have measurable cleaner current.
The bridge will work without, but I believe it is better to have include them.
 
rTate,

Go back and read from post #9 on this thread, I too asked all the questions you are asking now. BTW, use non- polarized caps in the snubbers. Or if you are stubborn like me, you can use high voltage rated polarized caps and verify their OK to use when derated for DC. Better to just use non-polarized caps.

Ron
 
Here's another question..
I've mounted the diodes on the heatsinks.
When I measure resistance, 6 of the 8 diodes have 0 ohms resistance
between the heatsink and the screw that secures them.
The other 2 show open between the screw and the HS.
I have used mica and thermal paste.

Is that reading normal??
 
If you are talking about screw to heatsink, then yes it is normal. You have just scratched the anodizing - no biggie. The backside of the diode is connected to the middle leg inside the diode, so if you have 0ohms between middle leg and heatsink, you have messed up the mica somehow. Still not really a problem though.
 
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