I need replacement chokes for 4850

[jason4207]

I already posted this in the 4850/4870 thread, but I figured a new thread would get more hits.

A friend is sending me his card. He was having some corruption after putting on an aftermarket HS, so he decided to remove it. Problem is he epoxied the RAMsinks on and he tore off two of the chokes!

http://img329.imageshack.us/img329/7081/img0083sd5.jpg


http://img255.imageshack.us/img255/9015/img0084xk0.jpg



The chokes are in pretty bad shape. Does anyone have a blown card, any spare chokes, or a link to where I can get some replacements? I'm going to try to fix it for him.

Thanks!

Jason

[Slovnaft]

I haven't done any looking myself, but these are the only sites I know of that might carry what you're looking for:

http://www.micrel.com/products.do

http://www.intersil.com/cda/home/

[jason4207]

Thanks for the links, but I'm not getting any hits when I type in the part number: R47 811 T28.

[Slovnaft]

that's probably because they don't carry the same manufacturer.
what you'd want to look for are electrically compatible chokes by any manufacturer, as you probably won't be able to access the same fab resources as ATI through any channel.

[jason4207]

Do you have any ideas on how I can find out what is compatible?

[jason4207]

Anybody?

[largon]

You could salvage them from virtually any motherboard/video card with four CPU phases, they don't have to be identical as long as you replace them all. Just don't take them from a board that has considerably more phases (8+).

[jason4207]

You could salvage them from virtually any motherboard/video card with four CPU phases, they don't have to be identical as long as you replace them all. Just don't take them from a board that has considerably more phases (8+).

Awesome news!

One problem...I don't have any dead hardware to take advantage of atm.

Does anyone have any dead hardware they want to donate to science? My friend will pay shipping!

:)

[jason4207]

My friend managed to get a hold of some dead cards.

2x 6800 Ultra, and a 6800GT.

Do you think these will have the parts I need? I don't think these cards are 4-phase.

And you mentioned that I need to replace them all, but they don't have to be identical. If that's the case then why can't I leave the 2 on there that are good, and just replace the other 2?

[largon]

I meant the new parts don't have to be identical to the originals. All the replacements should be identical.

[jason4207]

That makes a lot more sense. I'm guessing it has to do w/ load balancing.

So, just to make sure we're on the same page...

I want the finished repaired card to have 4 identical chokes on it. It doesn't matter too much where they come from as long as they're identical. Correct?

So, if the 6800Ultras have 2 chokes each I could use both of them from each card for a total of 4. Correct?

[Evilsizer]

jason,
check out www.digikey.com or www.mouser.com for SMD parts... it will prolly take a lot of searching but you should be able to find a replacement that way. the downside is that some parts have a min order like 5 or 10 in order to get the part you want. i would take a DMM and measure the resistance and the capacitance. then search thru the listed sites for a choke that fits the measurements and size. Either that or call up tech support for the video card company and see if they will tell you. another option is to hit up ViperJohn on OCF, he should know about the chokes...

[jason4207]

Good to see you over here Evil!

I've ordered plenty of stuff from both those companies. I'll wait till I get the card in my hands, and then take some measurements. Thanks for the advice!

[largon]

The problem with the chokes of a 6800Ultra is that the ancient GPU chomps away less than ½ of the power a RV770 does. Thus the inductors are likely rated for much lower currents than the originals on the busted HD4850.

[jason4207]

The problem with the chokes of a 6800Ultra is that the ancient GPU chomps away less than ½ of the power a RV770 does. Thus the inductors are likely rated for much lower currents than the originals on the busted HD4850.

I was afraid of that.

Wait a sec...half the power...half the number of chokes (assuming it has 2). It might still work, or am I thinking about it wrong?

I'll take some measurements before doing anything stupid.

[largon]

As far as I know, 6800Ultra has 3 vGPU coils.

[jason4207]

Doh!

[jason4207]

I got the card in my possession now along w/ some dead 6800's. Someone has told me they have a dead X1800.

http://www.techpowerup.com/articles/129/images/front.jpg

Will these chokes work?

[Evilsizer]

well in terms of cost in ordering mass amounts... it would make more sense they used the same PN between cards gens. just added more chokes to handle the added current, since from the basic view i see. all the chokes are in parallelfor circuit, thats makes for a higher current ablilty. now weither the same PN is used by NV to ATI is another matter.. i would go with ATI's last or 2nd to last gen card for chokes, if you cant find/get a pn to use.

were you ever able to measure the chokes with a DMM?

[philbrown23]

I have some chokes you could have but they are taller than the chockes on the 4850's

[jason4207]

well in terms of cost in ordering mass amounts... it would make more sense they used the same PN between cards gens. just added more chokes to handle the added current, since from the basic view i see. all the chokes are in parallelfor circuit, thats makes for a higher current ablilty. now weither the same PN is used by NV to ATI is another matter.. i would go with ATI's last or 2nd to last gen card for chokes, if you cant find/get a pn to use.

were you ever able to measure the chokes with a DMM?

I have my DMM, but it doesn't measure inductance or capacitance. Ohms showed up at 0.2, and of course voltage and amperage were 0.


I have some chokes you could have but they are taller than the chockes on the 4850's

Cool! Do you think they'll work...are they electrically equivalent?

[Nanometer]

find a data sheet, and find the part and try to match it. or, get the same gauge, and just count the number of coils.

[jason4207]

find a data sheet, and find the part and try to match it. or, get the same gauge, and just count the number of coils.

Here's the part number listed on the choke: R47 811 T28


I'm not sure how to find the data sheet. Google turns up nothing.


I might be able to further dissect one of the damaged chokes, and possibly figure out the gauge, and number of coils, though.

Thanks!

[largon]

Those on X1800 too are rated quite a bit lower than the originals. After all, X1800 peaks at *only* 100W.
R47 = 0.47µH, amperage needs to around 35A - or higher, there's no actual cap in amperage just as long as inductance is an approximate match to the original.

edit:
I guess I was way too vague when I said "you could salvage them from virtually any motherboard/video card with four CPU phases"...
:( :)

[Gautam]

I've got a dead 2900XT, I take it that could be of service?

Is it typical for the chokes to have the inductance listed on them? I can check mine out...

[largon]

Gautam,
HD2900XT has sort of "special" inductors (Pulse PA1314+PA1312). They're fysically and functionally incompatible with HD4850.
They'd fit in a HD4870 though...

[jason4207]

What about this?

http://www.alliedelec.com/Search/ProductDetail.aspx?SKU=8952531&MPN=IHLP-5050EZ-RZ-R47-M01&R=8952531&SEARCH=8952531&DESC=IHLP-5050EZ-RZ-R47-M01

0.47uH, and 38A...it looks like it might be about the same size as well.

[Boogerlad]

aren't 2900xt's digital vrm, thus not compatible with analog vrm?

[largon]

They're not any more digital than on other cards...
Just different type parts.

[jason4207]

What about this?

http://www.alliedelec.com/Search/ProductDetail.aspx?SKU=8952531&MPN=IHLP-5050EZ-RZ-R47-M01&R=8952531&SEARCH=8952531&DESC=IHLP-5050EZ-RZ-R47-M01

0.47uH, and 38A...it looks like it might be about the same size as well.

So, should I order these?

[largon]

They should work, they're even the same package type as the originals. And a bit higher rated I think.

[jason4207]

Well it looks that that part isn't in stock anywhere...at least not in sufficient quantities. I believe it is obsolete.

This product has similar specs, so I'll have to go w/ it unless somebody sees a reason not to.

http://www.cooperbussmann.com/pdf/8556d508-791a-49a9-b627-b942a55ab50a.pdf

[jason4207]

I ordered the part linked in the post above. Wish me luck!

[Slovnaft]

Keep posting on how this turns out.
i'm very interested.

[jason4207]

I forgot to update this...

I got the new chokes soldered in place w/o issue. The card booted, but it was doing the same thing that it was doing before the original chokes were ripped off. There were bad artifacts all the way through the boot process, and then shortly after getting to the desktop, the screen would go blank and one of the red LEDs would stay lit. The mobo also beeped 3 times. If I reset the PSU I could repeat this scenario.

Something went wrong while the original user was changing the HS. He used the epoxy-type TIM on the RAMsinks and VRMs. Before that the card worked fine.


The only thing I can think of to try is baking the card in the oven. My thinking is that one of the solder pads below one of the RAM chips is loose, but I'm really not sure. I sent the card back as it would have been very labor intensive to get the card prepped for an oven baking, and that would more than likely not help.