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Old 29th January 2007, 04:02 PM   #1
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Default Ixys Schottky and hexfred bridges

I was looking through my parts box to find some rectifiers for a gainclone project and I found the following rectfier bridges. Im not familiar with any of them and have never used them before. Anyone have any expereince with them?? Would any of them be suitable for use in the power supply of a 3886 gainclone amp?? Most people use discrete bridges built with MUR860, but since I have these laying around I thought maybe I could use them?


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Old 14th May 2007, 05:18 PM   #2
phi70 is offline phi70  United States
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Default IXYS bridges

I just had my 32A 1200V IXYS bridge pop on my counterpoint NPM last friday.

2 weeks ago I bought 2 IXYS
32A 1200V IXYS FRED Bridge Rectifier
to install into a power amp , swapout with a CM2502, with 60V AC input and max current of 25A.
(The mains rail supply bridge of a Counterpoint NPM amplifier)
One of them failed prematurely upon power on after working fine for 10 days.

This is the response from Michael Percy so I thought I should give a caution to fellow members:
"It is true that soft recovery diodes and bridges do not have as much surge current capability as standard parts, but this is rarely a problem unless you have a lot of power supply capacitance, in which case the turn on surge can look almost like a dead short, and a good argument for a soft start circuit. It is usually best to overkill with higher current parts where there is a large amount of power supply capacitance. The voltage rating of the bridges is not relevant here, just the current. I'm assuming the part was installed properly and failure was not due to a wiring error... michael"

I have 4 of those 600V 20A smaller bridges I plan to power the filaments of 2 6922 tubes in the NPMs and I am a bit worried now.
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Old 14th May 2007, 05:52 PM   #3
lgreen is offline lgreen  United States
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MUR860 are 8A, 600V, and the latter two items you list have higher current ratings. That should make you feel good about using them, no? I'll take that schottkey bridge off your hands!
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Old 14th May 2007, 07:19 PM   #4
jlw is offline jlw  United States
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Default Not chickening out... actually trying to move ahead

For the replacement of the main rail bridge I ordered the 68A 600V IXYS, and I will not power those puppies on until I get a slow soft start power supply.

For the filament supply bridges I will boldy move ahead despite the discouragement from the blowup last week.

No the problem is heatsinking. percyaudio does not have any matching heatsinks and I dont seem to be able to find matching clips for these flat i4-PAC form factor devices.
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Old 14th May 2007, 08:48 PM   #5
pjpoes is offline pjpoes  United States
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I made the heatsinks for mine. I do believe that simply bending some aluminum as needed is more than enough, but I actually made an aluminum plate and mounted my bridge to that. Works fine, dissipates more than enough heat.
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Old 14th May 2007, 10:17 PM   #6
jlw is offline jlw  United States
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Default how did you attach the bridge to the pc of Aluminum?

My challenge is there is no hole for a screw and the TO-XXX compatible clips are too thin for this IXYS.
Did you use thermal heatsink tape or some other means of securing the bridge?
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Old 15th May 2007, 12:02 AM   #7
pjpoes is offline pjpoes  United States
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oh I guess I didn't look at which ones you are using sorry, mine have holes. Sorry, mine are in the to-220 style. Those have the holes for it. I would think you could still bend a piece of metal to make your own clip, no? Sorry about that though, I should look more carefull before replying. I saw a post about Ixys diodes and got all excited, hehe, because I have switched to using those exclusivly. I got mine from either Digikey or Mouser, don't remember which, and ordered I think around 50 of each value I got. They were both rated for 1200 volts but different amps, I think 20 and 60 maybe, something like that. I happen to like them, I had some problems with others blowing from too much turn on current, and someone else mentioned getting higher rated ones, and the Ixys were recomended. I think they are a decent quality product at a decent price, some are a bit pricey, but mine were competitive with other good schotkys.

My Meixing tube amp had pretty poor quality chinese sourced diodes made into a full wave bridge, and I remade it using the to-220 style which made a difference. Even before rebiasing the amp it lowered the noise floor noticably, then adding the bypass caps and replacing the bias resistors and rebiasing the amp, for other reasons, fixed the problem for good. I know thats off subject, just the context of my use. I used up some remaining MUR860's and they "popped" at startup, I then replaced them with the new IXYS and made the heatsink, which fixed the problem.
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Old 15th May 2007, 03:42 AM   #8
phi70 is offline phi70  United States
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Default Must be fun to mod the Mingdas

No problem. Glad to hear someone with good experience with the IXYS. Problem is I heard from some people that while their FRED diodes are great, the bridges are not quite robust.
That's why I am a bit cautious with using the 600V 20A bridges even for filaments.

I know that with the Mingdas, swapping the 12AX7 with 5751 tames the sound quite a bit. Next of course is the coupling caps.
I'm glad to hear that rectifiers make a difference.
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Old 3rd May 2008, 10:16 AM   #9
col is offline col  Australia
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pipoes, are these the same ones as you have?

http://docs-asia.electrocomponents.c...6b80a35ef0.pdf

I'm interested in trying some with a 2 x Hypex UcD180 setup with a 300VA transformer. I'm currently using 2 X KBPC3504 bridge rectifiers with 47nF bypasses feeding 4 x 10000uF 63v Nichicon Gold Tune. Iv'e heard that the IXYS FRED stuff is better though and these seem reasonably priced enough to have ago. I'm wondering if they will handle the current?
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Old 8th May 2008, 05:34 PM   #10
pjpoes is offline pjpoes  United States
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Yes I believe those are the same ones I have. I think I ordered them through either Digikey or Mouser (Whoever carries them). It's been a while since I used those, but I can say that the tube amplifier and solidstate amplifier projects using them are all still working properly.

As an update to some others concerns, I to have now used an Ixys bridge which failed early. It was attached to a massive power supply with 47,000uf's at 100 volts capacitors, then two 11mh inductors, and then 4-22,000uf 100 volt capacitors. Not only did it blow the bridge, it also blew the rail fuses multiple times. I have since added a softstart, and this is a null issue. I would also add though that replacing the bridge rectifiers with more traditional IR bridges did keep the bridges from failing, though fuses remained an issue.

Your setup is dealing with so much lower current that I would be amazed if you had problems. Again, mount them to some aluminum and I see no issues. Probably unmounted they would be fine, but why not give them a little extra protection. The ones I had problems with were hooked to a much larger CLC power supply with 1.8kva power transformer, 47mf at C1, pretty sizable inductors, and 44mf at C2, the diodes essentially saw a deadshort across them at C1, and had a huge transformer to feed them far more current than they could handle.

None the less, if you are worried, use a softstart, if you aren't already, that will solve any concerns. These diodes don't fail from the normal current, those are well within their ratings. It's the startup currents which can exceed 100amps, so I am told, with large enough parts. Even your setup probably has in excess of 50 amp surges at startup.
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