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Old 20th March 2006, 07:03 AM   #1
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Default The "Cheap, but good" rectifier & diode thread.

After seeing how a full set of rectifier diodes for a chip-amp would cost me a whopping 20$, I realized that a set of guidelines for decent, low-cost options for rectifiers was in order. (Keep in mind that the rest of the amp comes out to around 30$, including transformers.) For example, being a newbie, I've heard that some rectifiers (like Schottky diodes) require extra caps to prevent "ringing".
For example:
The 1N5404. These go for about fifteen cents per, and are rated for 3 amps at 400 volts. Do these work well? (And can they be paralelled to increase their current rating?)

Also, I found some 6A @ 200v rectifier diodes at All Electronics. They look to be similar to the MUR820's popular with chip-amps. Any thoughts?
http://www.allelectronics.com/cgi-bi...P_200PIV_.html

Finally, a really inexpensive bridge rectifier: 1$ for 200V at six amps!
http://www.goldmine-elec-products.co...?number=G14526
These look pretty nice for the price. (That said, who can argue with 2$ for the equivalent of 8 diodes?)

EDIT:
I've found MUR820's for under sixty cents a pop!
http://www.mouser.com/index.cfm?hand..._pcodeid=51151
MUR860's are more than twice the price.
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Old 20th March 2006, 08:56 AM   #2
lndm is offline lndm  Australia
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Default Re: The "Cheap, but good" rectifier & diode thread.

Quote:
Originally posted by Spasticteapot
can they be paralelled to increase their current rating?
Unfortunately this is never a good idea as diodes don't share current evenly.
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Old 20th March 2006, 09:13 AM   #3
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Default Re: Re: The "Cheap, but good" rectifier & diode thread.

Quote:
Originally posted by lndm


Unfortunately this is never a good idea as diodes don't share current evenly.
Yes, if you do it you should add current balancing resistors in series with each diode. Likewise, if you put diodes in series you should add voltage balancing resistors in parallel with each diode.
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Old 20th March 2006, 09:35 AM   #4
AndrewT is offline AndrewT  Scotland
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Hi,
add about 0r22 in series with each diode before you build them into the bridge. This adds to the R in a RC PSU.

It has the advantage of reducing the peak current pulse at the expense of increasing the voltage droop under load.

Look up PASS gigantic (or similar name) PSU, he has done exactly that.
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Old 20th March 2006, 10:24 PM   #5
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Default Re: The "Cheap, but good" rectifier & diode thread.

Quote:
Originally posted by Spasticteapot

Finally, a really inexpensive bridge rectifier: 1$ for 200V at six amps!
http://www.goldmine-elec-products.co...?number=G14526
These look pretty nice for the price. (That said, who can argue with 2$ for the equivalent of 8 diodes?)

You can find those bridges in almost any PC power supply. I have one or two of these kicking around that I pulled from PC power supplies. I could mail you one for the cost of postage and a bubble mailer. However, postage and packaging is more than what they cost at Radio Shack.

http://www.radioshack.com/product/in...ductId=2062583


Where are you finding a suitable gainclone transformers for only $30?
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Old 21st March 2006, 12:25 AM   #6
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Can someone give me a idea why fast discrete diodes are better than bridges? For a ps? Seems that 60hz is about as slow as it gets. I can see the reason for a switching ps.
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Old 21st March 2006, 01:23 AM   #7
jcx is offline jcx  United States
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really great forum search there guys...

but you missed this thread:

Best diodes for generic power supply
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Old 21st March 2006, 01:33 AM   #8
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Quote:
Originally posted by jcx
really great forum search there guys...

but you missed this thread:

Best diodes for generic power supply

been there, read that
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Old 21st March 2006, 02:44 AM   #9
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I've heard that these are better in double-blind tests, and I'm inclined to believe them. Plus, it's 5$ difference, if I can get the diodes from the folks on E-bay. People pay more than that on binding jacks.

Also, GC suitable transformers can be had for 16$. ApexJr sells 24v @ 7A (168VA) transformers for 8$ each; just use one for each winding. Presto! Instant 336VA goodness!
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