The mystery of the rusty chokes

New boards come with rusty choke bonus

Radeon logo iconSOME OF YOU might not be old enough to remember the farce about a decade ago about blown capacitors on motherboards. It was a huge issue and came down to the matter of poor choice of components as the motherboard makers tried to save some cost. Although we’re not the first to unearth this, it now appears that a certain manufacturer has ended up with at least some board models that come with pre-rusted chokes.

Update 2: Second part of the series here.

Now we feel that it’s our duty to report this issue, not because we want to get the company in trouble, but because we owe it to our readers. The matter of the fact is that the rusty chokes could cause a catastrophic failure of the motherboard they’re fitted to and fry the CPU mounted on the socket in the motherboard. From what we’ve found out it seems like the issue so far is limited to a range of P43, G31 and AMD 785G boards.

Normal Chokes

If you look at the picture above you see what the chokes should look like. These are iron core chokes, so if you know for certain that your motherboard has ferrite core chokes; you’re not under any circumstances going to have this issue. Iron core chokes are usually found on mid to low-end boards these days with higher-end models using the more expensive ferrite core chokes.

Iron core chokes are coated in a clear lacquer to prevent rust. Iron is a metal that rusts easily and this is something that’ll happen much faster when the iron comes in contact with moisture. Normally this doesn’t really happen inside a computer unless you live in a very damp climate. Even so, the lacquer coating should prevent this from happening.

Rusty Choke

Take a look at the picture above and compare it to the first picture, see something different? Not only has the choke changed colour, but you can clearly see the rust underneath the lacquer.

Rusty Choke

Here’s another example from a different board model that shows the same rust patterns and colour changes.

Rusty Choke

If you thought the previous pictures were bad, then think again while observing these smaller chokes from a 12-phase motherboard.

Rusty Choke

And from above.

Rusty Choke

Here’s a close up of these chokes, notice the bubbles. We’ve never come across anything like this before and it’s fairly clear that the rust is coming from the inside of the chokes with the moisture trapped inside trying to get out.

Rusty Choke

Here’s a slightly less severe case from an AMD chipset board.

There’s a little bit more to this story, though. By now we’re sure that some of our more eagle eyed readers have figured out that Asus is the motherboard company in question. It’s easy to say that this is a quality control issue, but it turns out that most of these boards were manufactured some six to eight months ago. At least some of the models won’t have been popular models and as such not sold at the rate they were manufactured.

This means that when the quality control was done, none of these issues would’ve been visible. A probable explanation to the rust is that the iron powder used to make the iron core chokes had water added to it during the milling process and the iron powder was then not dried sufficiently before the chokes were made. The moisture trapped inside the chokes has then started to rust the chokes from the inside out during the time these boards have been sitting in the warehouse.

From what we know at the moment, this issue seems to be a local issue in Taiwan and Singapore, but it might be much more widespread than this. The issue that we’re having with it all is that any responsible company would pull these products off the market. Instead we’ve heard that Asus is actually dumping the pricing on the affected models we’re aware of to try to clear its inventory as quickly as possible.

The models known to be affected include the P5P43TD, the P5P43TD Pro (Intel P43 chipset), the P5G31D-M Pro (Intel G31 chipset), the M4A785-M and the M4A785D-M Pro (AMD 785G chipset). If you own one of these boards we’d suggest that you visually inspect the chokes for any signs of rust and contact your reseller ASAP if you discover any, as it should be replaced under warranty.

Potentially this could be a significant RMA issue for Asus, but as we don’t know how many boards are affected by this issue, it’s hard to tell how big of a problem this is. As we mentioned at the beginning, we weren’t the first to discover this and you can find pictures by owners of these boards here, here and here, as well as some pictures of a board unboxing here where the author seems to have completely missed the fact that the chokes were covered in rust.

Another potential issue is that ASRock and Pegatron products might suffer from the same problem, but this has not been confirmed as being the case at the time of writing. However, Asus, Pegatron and ASRock have sourced products together in the past and could potentially have sourced chokes from the same supplier.

Update: Asrock has responded to SemiAccurate and said that it doesn’t use chokes from the same manufacturer.

We’re expecting that Asus will be in touch with us and hopefully it can offer an explanation as to what is going on. Let’s just hope Asus honors the warranties for these boards, or else there are going to be a lot of upset customers out there. Please let us know in our forums if you’ve got a board suffering from rusty chokes.S|A

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