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Old 18th December 2003, 10:50 PM   #21
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Hi,

one thing: when testing the PSU check the temperature of the diodes, as I see there is no additional cooling.


On my first JLH amp I used a 50A bridge-rectifier and that needed some cooling (I screwed that to the bottom of the amp-housing)

On my second JLH-amp I built the rectifier from RURG3060's and mounted
those on a alu U profile:
Click the image to open in full size.
At full load this warms up nice.

I'm not quite sure the 3A / 4A diodes will survive the inrush current when the amp is switched on.
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Old 19th December 2003, 08:15 AM   #22
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Default Re: Re: Wohoo!

Quote:
Originally posted by millwood
what do you have those magazines for?
Those were not mine .

Quote:
Originally posted by millwood
Nice PCB. How do those cutting discs work?
Thanks! They are cutting discs for the dremel. Just put them on the dremel, mark the size of the PCB and cut a piece out of the standard PCB you buy in a store.

Quote:
Originally posted by dutch diy
one thing: when testing the PSU check the temperature of the diodes, as I see there is no additional cooling.
I plan on glueing a DIP heatsink on the diodes with special cooling paste/glue. A DIP16 heatsink should fit nicely.

Quote:
Originally posted by dutch diy
I'm not quite sure the 3A / 4A diodes will survive the inrush current when the amp is switched on.
Geoff told me that too. I guess I'll have to look for other diodes then.
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Old 19th December 2003, 04:16 PM   #23
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I guess I'll just keep bumping my own thread .

I used with the 4A diodes anyway, since I plan on putting an inrush current limiter (soft start) circuit in front of the PS.

Here's a picture, ain't it cute :
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File Type: jpg power supply - final.jpg (26.4 KB, 647 views)
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Old 19th December 2003, 04:24 PM   #24
Tyimo is offline Tyimo  Hungary
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Default PSU Voltage

Hi!
May be here is the right place for this question:
What is the max PSU voltage for the JLH 1996 version?
I have a nice 300VA 2X24 V Hipersil transformator and I would like to use for the JLH updated amp, in a non-regulated PSU, but I don't know the 30V isn't too high?
(Somewhere I read that 60 V is the max and 40 V is the optimum for the 1969 version.)
Thanks
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Old 19th December 2003, 05:07 PM   #25
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I wouldn't worry too much about in-rush currents: those diodes are surprisingly resilent, . I am using GBU8 bridge for my products. Those are rated at 8amp continues, but can take 200amp rush current.

unless you are using some huge capacitors, I wouldn't worry too much about the diodes.
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Old 19th December 2003, 05:25 PM   #26
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Are 22 000F caps considered huge? Now I only have to find a heatsink for them, since my supplier didn't have DIP16 sinks.
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Old 19th December 2003, 05:35 PM   #27
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Quote:
Originally posted by Devil_H@ck
Are 22 000F caps considered huge? Now I only have to find a heatsink for them, since my supplier didn't have DIP16 sinks.

I did a quick simulation. assuming a 22v peak transformer, a 22000uf cap with 40mohm esr, half wave rectification (for simplicity). the inrush current is about 120a, and charging current about 30amp (should be 15amp if you use a bridge).

it sounds like pushing the limit on the inrush current for a 4amp diode.

as to heatsinks, i am not sure if you need one. I ran my gbu8k at 5amp for extended period of time, without any heatsink. it feels just "warm" (like slightly above the temperature of my hand).

so try it without heatsink first and see if that works.
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Old 19th December 2003, 07:32 PM   #28
azira is offline azira  United States
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this is because I don't know something and not becuase i know something you don't.. cause i probably don't.

Why the purpose of using discrete diodes instead of a bridge rectifier?
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Old 19th December 2003, 11:47 PM   #29
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Well, I don't really know why I used discrete diodes . Probably because they don't look at like a bridge rectifier on the schematic (eg. not in the typical square form). And I happened to come across some ultra fast diodes. I guess that's why .

The max inrush current for the diodes is 125A actually, so that is indeed close to the limit. Well, I guess only time and experience will tell .

Btw, I just made the 2nd PCB board. Except for the fact that I cut this one even more 'not-straight', it came out very well. The discovery of a microwave to warm up the etching substance sure is nice .

Here's the 2nd PCB, not that it's that exciting, but I have to test the newly acquired Canon PowerShot A70, don't I ?
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File Type: jpg power supply - pcb 2.jpg (9.8 KB, 546 views)
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Old 20th December 2003, 06:33 AM   #30
azira is offline azira  United States
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Cool, just asking. I'll stick with my bridges then

My friend made all his own PCBs for his senior project. He was able to mount some pretty small surface mount components too. Pretty amazing for a laser printer and a Kinkos copier.

But anyway, he told me the same thing, heat up the water and it works faster, but watch out. He heated it up too much that as soon as he dropped it in the etching solution it etched away all his traces too.
--
Danny
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