Badcaps.net Forum
Go Back   Badcaps Forums > Troubleshooting Hardware & Devices and Electronics Theory > Troubleshooting Power Supplies and Power Supply Design
Register FAQ Calendar Search Today's Posts Mark Forums Read

 
Thread Tools Display Modes
Old 02-05-2020, 07:59 AM   #1
leotron
New Member
 
Join Date: Apr 2019
City & State: Colonie
My Country: Offworld
I'm a: Knowledge Seeker
Posts: 15
Default XFX 850w blown bridge rectifier.

Hi, a friend of mine gave me this broken power supply, aparently it's the rectifier bridge that was damaged months ago. He took it to a technician and they didn't have the repair tools necesary but they remove the original bridge rectifier since it was damaged(burned). I have some of this rectifiers laying around, but they are not the same. The original its a pair of GBJ1506

And I have KBL06 , KBL406 , RVB406, D5SBA20, D3SBA60, GBU608. Most of them have similar values to the original, but I'm not planning to use the PSU at full load (ie: SLI, an I7 processor, etc).

TomsHardware https://www.tomshardware.com/reviews...su,4581-3.html

Thanks in advance for your time!
Attached Images
File Type: jpeg WhatsApp Image 2020-02-05 at 10.49.13.jpeg (91.2 KB, 39 views)
File Type: jpeg WhatsApp Image 2020-02-05 at 10.49.24.jpeg (96.9 KB, 37 views)
leotron is offline   Reply With Quote
Old 02-06-2020, 10:26 AM   #2
leotron
New Member
 
Join Date: Apr 2019
City & State: Colonie
My Country: Offworld
I'm a: Knowledge Seeker
Posts: 15
Default Re: XFX 850w blown bridge rectifier.

I'm sorry I didn't wrote my question, it is posible to replace the original bridge with the replacements that I have? I'm planning to put a large heatsink in top of them.

Thanks for reading.
leotron is offline   Reply With Quote
Old 02-06-2020, 11:04 AM   #3
eccerr0r
Solder Sloth
 
eccerr0r's Avatar
 
Join Date: Nov 2012
City & State: CO
My Country: USA
Line Voltage: 120VAC 60Hz
I'm a: Hobbyist Tech
Posts: 4,619
Default Re: XFX 850w blown bridge rectifier.

you're probably perfectly fine with the two KBL06 , KBL406 , RVB406, D3SBA60, or GBU608 in parallel - but you should use two identical units and should make sure both are well touching each other for thermal equilibrium. No heatsink is needed if the originals didn't have one though I don't think any of these really could benefit from one due to thermal resistance.

If the two originals were attached together then perhaps some circuit mods are needed to accommodate...or just run at low load, say no more than 300W.

I'd still try to find out why the bridge blew. These things usually do not blow.

Last edited by eccerr0r; 02-06-2020 at 11:08 AM..
eccerr0r is offline   Reply With Quote
Old 02-06-2020, 12:41 PM   #4
R_J
Badcaps Veteran
 
Join Date: Jun 2012
City & State: ☻
My Country: Canada
I'm a: Professional Tech
Posts: 5,734
Default Re: XFX 850w blown bridge rectifier.

The GBJ1506 is a 15 amp 600volt bridge, The KBL06, for example, is only rated at 4 amps 200v
R_J is offline   Reply With Quote
Old 02-06-2020, 02:15 PM   #5
Quaddro
Tukang Kentu
 
Quaddro's Avatar
 
Join Date: Nov 2010
City & State: Yogyakarta
My Country: Indonesia
Line Voltage: 220VAC 60Hz
I'm a: Hobbyist Tech
Posts: 106
Default Re: XFX 850w blown bridge rectifier.

Quote:
Originally Posted by R_J View Post
The GBJ1506 is a 15 amp 600volt bridge, The KBL06, for example, is only rated at 4 amps 200v
Good only for testing, but not for continuous usage..
Quaddro is offline   Reply With Quote
Old 02-06-2020, 05:04 PM   #6
eccerr0r
Solder Sloth
 
eccerr0r's Avatar
 
Join Date: Nov 2012
City & State: CO
My Country: USA
Line Voltage: 120VAC 60Hz
I'm a: Hobbyist Tech
Posts: 4,619
Default Re: XFX 850w blown bridge rectifier.

I don't think it's possible to run 15A into even a GBJ1506 if it didn't have a heatsink, hence the suggestion that the lower units may be fine if there wasn't a heatsink to begin with (none of those little dinky pieces of metal, the heatsink needs to be somewhat elaborate, probably need at at least around 50cm^2 surface area).

I thought I saw the KBL06 able to handle [email protected], agreed this is not sufficient for the full wattage of the supply, but should be okay for low wattage usage as well as inrush.

FIND OUT WHY THE BRIDGE BLEW, IT'S NOT SUPPOSED TO BREAK THIS WAY!!!
eccerr0r is offline   Reply With Quote
Old 02-06-2020, 05:32 PM   #7
leotron
New Member
 
Join Date: Apr 2019
City & State: Colonie
My Country: Offworld
I'm a: Knowledge Seeker
Posts: 15
Default Re: XFX 850w blown bridge rectifier.

Thanks to all of you for the answers, the PSU may be in short circuit. This ia stock image from TomsHardware that shows the heatsink.

leotron is offline   Reply With Quote
Old 02-06-2020, 06:33 PM   #8
eccerr0r
Solder Sloth
 
eccerr0r's Avatar
 
Join Date: Nov 2012
City & State: CO
My Country: USA
Line Voltage: 120VAC 60Hz
I'm a: Hobbyist Tech
Posts: 4,619
Default Re: XFX 850w blown bridge rectifier.

Okay that's not a good sign if it needed a heatsink stock, you will need to locate new 15A units if you want to run at 850W again, else you're stuck to do 250-300W until you do so.
eccerr0r is offline   Reply With Quote
Old 02-11-2020, 09:25 PM   #9
momaka
Badcaps Veteran
 
momaka's Avatar
 
Join Date: May 2008
City & State: VA (NoVA)
My Country: U.S.A.
Line Voltage: 120 VAC, 60 Hz
I'm a: Hobbyist Tech
Posts: 9,245
Default Re: XFX 850w blown bridge rectifier.

Quote:
Originally Posted by eccerr0r View Post
FIND OUT WHY THE BRIDGE BLEW, IT'S NOT SUPPOSED TO BREAK THIS WAY!!!
+100 ^ This!

If you have a blown bridge rectifier, chances are there is something else wrong with the PSU. It could be something as simple as blown MOVS (due to repeated power surges) or because of a blown APFC section (which is not so uncommon.) I'm betting on the latter, unfortunately.

That said, >>for testing<< the PSU, you can use any of the bridge rectifiers that are rated for at least 500V reverse voltage.

I personally suggest removing both GBJ1506 bridge rectifiers and testing both of them. If one is good, you can use just that rectifier and not have anything else with it in parallel. This actually won't really limit the output power of the PSU that much, if at all.

Quote:
Originally Posted by eccerr0r View Post
Okay that's not a good sign if it needed a heatsink stock, you will need to locate new 15A units if you want to run at 850W again, else you're stuck to do 250-300W until you do so.
Not at all.
The only reason the manufacturer put a heatsink on those two 15A bridge rectifiers is for thermal coupling (and rather poor at that, but still better than nothing.)

The reason for the two 15A bridge rectifiers is to increase the efficiency: less current going through a diode means less power dissipated. Since diodes have non-linear power dissipation vs. current, you want to keep the current as low as possible across the bridge rectifier for lowest power dissipation (and thus, increased efficiency.)

But that doesn't mean that a single 15A bridge rectifier is not enough. Even if the PSU is used in a country with 120V AC line and the PSU has 80% efficiency when loaded... for a 850W PSU loaded with 800W of load (just making these numbers to make it easier to calculate), the PSU will be drawing roughly 1000W from the wall. @ 120V AC, that means it will be pulling roughly 10 Amps (let's say the line drops quite a bit under load with those 1000W, just for "worst case" scenario.) Many of these bridge rectifiers will still handle that 10A of current just fine. They will run absolutely hot, though... - Hence, the installment of two 15A parts in parallel. But in reality, even a single 15A bridge rectifier will likely be able to manage the full load on that PSU. And if living in a country with 230/240V AC, the current drawn will be half. So if you do live in a country with 230/240V AC, I wouldn't even worry about using just a single 15A bridge rectifier and leaving the PSU with just that.
momaka is offline   Reply With Quote
Old 02-20-2020, 01:11 AM   #10
eccerr0r
Solder Sloth
 
eccerr0r's Avatar
 
Join Date: Nov 2012
City & State: CO
My Country: USA
Line Voltage: 120VAC 60Hz
I'm a: Hobbyist Tech
Posts: 4,619
Default Re: XFX 850w blown bridge rectifier.

Eh... no, math does not check out. You're not going to even remotely halve system power loss by doubling the diodes. You will save some power but it's a drop in the bucket.

However you will spread out the heat generation. This strategy is frequently used and is the main reason why a lot of components are doubled up when possible. But this means that one will need to recreate the original situation when running in the original situation...

... unless the heatsink was insufficient to begin with, and hence the bridge failed...

Last edited by eccerr0r; 02-20-2020 at 01:14 AM.. Reason: removing ambiguity ... english is a miserable language and hence people love arguing in english
eccerr0r is offline   Reply With Quote
Old 02-25-2020, 10:15 PM   #11
momaka
Badcaps Veteran
 
momaka's Avatar
 
Join Date: May 2008
City & State: VA (NoVA)
My Country: U.S.A.
Line Voltage: 120 VAC, 60 Hz
I'm a: Hobbyist Tech
Posts: 9,245
Default Re: XFX 850w blown bridge rectifier.

Quote:
Originally Posted by eccerr0r View Post
You're not going to even remotely halve system power loss by doubling the diodes. You will save some power but it's a drop in the bucket.
That, I agree with. But with these super-efficient PSUs, every "drop" counts a little.

Quote:
Originally Posted by eccerr0r View Post
... unless the heatsink was insufficient to begin with, and hence the bridge failed...
That heatsink would probably be insufficient only if the PSU was at 100% load on 120V AC line that was dropping a bit low (110-115V maybe) and the PSU was ran like that for long periods of time so the B.R. had time to overheat and go bad.
momaka is offline   Reply With Quote
Old 02-27-2020, 01:37 AM   #12
eccerr0r
Solder Sloth
 
eccerr0r's Avatar
 
Join Date: Nov 2012
City & State: CO
My Country: USA
Line Voltage: 120VAC 60Hz
I'm a: Hobbyist Tech
Posts: 4,619
Default Re: XFX 850w blown bridge rectifier.

Staring at the datasheet, I think the waste power by running a single rectifier at higher current versus two would be less than 1W at around 900W system dissipation. Making sure the two rectifiers were balanced to realize this power saving potential is another problem...

Drooping from 120V to 110V at full load will increase rectifier dissipation by about 1W... I sure hope that heatsink can handle a 1W power increase.
eccerr0r is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump



Badcaps.net Technical Forums 2003 - 2020
Powered by vBulletin ®
Copyright ©2000 - 2020, Jelsoft Enterprises Ltd.
All times are GMT -6. The time now is 06:46 AM.
Did you find this forum helpful?