Changing to Polymer Capacitors Help!

[Alup]

ok so my company has decided to let me repair all the bad dell optiplex 745 motherboards, Now all these mother boards have 1 major issue with them bad caps. there are 4-9 bad caps on every one of these and they went bad because of heat.

What i want to do is replace the current caps with Polymer Capacitors to avoid alot of the current issues is this possible?

the current values of the caps are
5 of - 1800uf | 6.3v | 20%
4 of - 2200uf | 6.3v | 20%

I found some Polymer ones on mouser that have the same rating as the current ones can i use these?
http://www.mouser.com/ProductDetail/...VHTkPLvHASU%3d

or do i need to have different caps to replace these? thank you in advance!

[mockingbird]

Re: Changing to Polymer Capacitors Help!

I think Nichicon Polymer LG (Not to be confused with the electrolytic Nichicon LG, whose datasheet Mouser mistakenly links to) is a suitable polymer series for replacing VRM electrolytics, however you should halve the capacitance. You must also isolate all of the VRM caps so that you only halve the capacitance of the VRM caps.

You should ask Topcat for help, because I'm sure he's done polymer mods to 745. In his pre-made kit page, he lists the SFF and uSFF Optiplex 745, but those are electrolytic pre-made kits.

[smason]

Re: Changing to Polymer Capacitors Help!

Which formfactor? If they're the tiny case ones, yeah do polys, those things run way too warm, but it they're the full size tower, good quality regular caps should be fine.
I've got a ton of full size 745s here all running fine.

[Alup]

Re: Changing to Polymer Capacitors Help!

All the ones with the massive cap issues are SFF Computers

[c_hegge]

Re: Changing to Polymer Capacitors Help!

Use https://www.badcaps.net/store/produc...roducts_id=134 for the 1500uF caps (assummung they are not in the CPU VRM)

Use https://www.badcaps.net/store/produc...products_id=77 for the 1800uF caps (assumming they are in CPU VRM)

[Alup]

Re: Changing to Polymer Capacitors Help!

Use https://www.badcaps.net/store/produc...roducts_id=134 for the 1500uF caps (assummung they are not in the CPU VRM)

Use https://www.badcaps.net/store/produc...products_id=77 for the 1800uF caps (assumming they are in CPU VRM)

the ones you linked to are way different rating's than what i need.

my question is what do i need? im not quite sure how to convert this board.

here are the caps that i need to replace.the four large circles in the middle of the board are the 2200's and the 5 smaller circles are the 1800's

[mockingbird]

Re: Changing to Polymer Capacitors Help!

I wouldn't bother.

The VRM is already all polymer capacitors. The ones I would replace would be just the ones that say "KZJ" on them. The Rubycons look OK. The KZJ should be replaced with Samxon GC/ Nichicon HN/ Rubycon MCZ.

So, I understand you're repairing a few of these for your company... Just replace any of the "KZJ" caps. The Rubycons look ok.

I also read in this forum that the PSUs have failed caps. You might want to take a look inside them too.

[Alup]

Re: Changing to Polymer Capacitors Help!

I wouldn't bother.

The VRM is already all polymer capacitors. The ones I would replace would be just the ones that say "KZJ" on them. The Rubycons look OK. The KZJ should be replaced with Samxon GC/ Nichicon HN/ Rubycon MCZ.

So, I understand you're repairing a few of these for your company... Just replace any of the "KZJ" caps. The Rubycons look ok.

I also read in this forum that the PSUs have failed caps. You might want to take a look inside them too.

Sure enough the PSU had 2 bad 2200uf 10v caps in it oddly enough the caps in the psu are rated at 80c and not at 105c like the rest. that will change!

thanks for the heads up on that one.

Would these work for replacements? I have to buy from mouser as that is the company that our company is in a contract with.

2200 For MOBO = http://www.mouser.com/ProductDetail/...%252bL2y7H0%3d
1800 For MOBO = http://www.mouser.com/ProductDetail/...NgHrZlUloDw%3d
2200 for PSU = http://www.mouser.com/ProductDetail/...NpnnhUzRTlQ%3d

[mockingbird]

Re: Changing to Polymer Capacitors Help!

I think you need to take a step back and re-think this job.

If this power supply is failing, probably ALL the 745 PSUs have some sort of problem. If you want to take this job seriously, you need to open up this power supply, examine every single capacitor, write yourself a BOM (Bill Of Materials), and only then proceed to order what you need.

You should not just change the two bulged caps in the power supply. There are many threads in here about re-capping a power supply. You should completely re-cap all the PSUs because DELL PSUs often contain many substandard capacitors.

You also need to know how to re-cap a PSU. You need to get the right kinds of capacitors. It's not just a matter of temperature rating. There is also the matter of ESR and ripple ratings to consider.

I didn't say that you shouldn't worry about the type of cap you use on the motherboard. I said that it's probably unecessary to use polymers, because it would only complicate matters and not give you very much benefit.

Your machines basically have to issues:
1) Dell uses a mix of Japanese capacitors. Rubycon, Nichicon and United Chemicon. All the capacitors that these companies make are reliable, EXCEPT for the low-ESR motherboard capacitors of United Chemicon. That's the black capacitor you posted in the pic with the gold letters that say "KZJ". All of your motherboards with United Chemicon KZJ or KZG capacitors should be replaced. KZJ must be replaced with Nichicon HN, Rubycon MCZ, or Samxon GC, and KZG can be replaced with either HN/MCZ/GC or HM/MBZ/HM.
2) The power supplies also have failing capacitors. If the power supply is failing, it's passing ripple (AC current) to the motherboard's capacitors. Yuo need to completely re-cap each and every PSU. Once you have a BOM for one, then you're set, because you order the same parts for all the PSUs. With the motherboards, it's not so. Dell may use KZJ and MCZ interchangeably in different places on each 745 motherboard.

[Alup]

Re: Changing to Polymer Capacitors Help!

well i am about to recap about 60 of these machines and only about 1/8th of them have had PSU issues.

I will do my normal routine and look in every PSU but replacing every cap in the psu is not cost effictive so that will not happen. most likely the ones with bad PSU's will be trashed.

The way that my company looks at it is this.
A new computer is 500 dollars
A re-capped old computer = 20 dollars
A Dell repair with no warranty is 100 dollars plus at that time we can get the extended warranty for another 50.

so if the price exceeds a certain amount they will not even consider it.

I just went through and tested every cap on the psu and all came back to the correct uf/voltage so im willing to bet i got lucky and the 2 2200's that i found to be bad are the only ones.

sorry for all the questions, I can repair/make just about any circuit but caps were always my downfall considering that there are so many different variants and types and such.

[c_hegge]

Re: Changing to Polymer Capacitors Help!

For replacements, the ones you linked to will be fine for the motherboard, but don't use HN in a power supply. Use either PW or HE series there.

[mariushm]

Re: Changing to Polymer Capacitors Help!

If your time is not a factor (you're paid the same no matter if you replace 2-3 capacitors or 10), you can argue it's worth replacing all because it will be cheaper to buy the capacitors in volume.

For example:

http://search.digikey.com/us/en/prod...1472-ND/589213

HE is $0.67 a piece, but it's $0.33 when buying 100, $0.31 for 250... so you might as well buy 250-500 pieces and replace everything, it will still cost about 5-10$ per PC.

[mockingbird]

Re: Changing to Polymer Capacitors Help!

The way that my company looks at it is this.
A new computer is 500 dollars
A re-capped old computer = 20 dollars
A Dell repair with no warranty is 100 dollars plus at that time we can get the extended warranty for another 50.

If I were you, I would avoid this headache and let your company send those machines off to Dell for their warranty. It will not be as good as if you do the work, but ordinary companies will never reward their employees for quality. Dell's warranty will consist of replacing the motherboards and in some cases PSUs, with equivalent parts that will probably fail in the future. So why bother? By the time the replacements fail, your company will probably order new machines anyway.

I just went through and tested every cap on the psu and all came back to the correct uf/voltage so im willing to bet i got lucky and the 2 2200's that i found to be bad are the only ones.

You can't test capacitors like that. You need to test ESR.

[999999999]

Re: Changing to Polymer Capacitors Help!

Let's say it takes an hour each box. They were only worth what, $100 by now IF working?

You should tell them that it is not time effective to repair more than a few boards and PSU as spares for emergency purposes and to ramp up the replacement schedule, possibly trying to negotiate with Dell for a discount since you were stuck with so many bad boxes.

[c_hegge]

Re: Changing to Polymer Capacitors Help!

^
I'd say around $300 if working (assuming 1GB RAM and a 160GB HDD).

[999999999]

Re: Changing to Polymer Capacitors Help!

^ I've seen them on sale for about $100 USD, no way any system without a high end video card (for it's time) is worth $300, especially a small form factor one with "issues".... though I am talking about the American market. In the US such a failed system is worth $0, maybe something if willing to part it out but doing so and reselling the parts takes time which is worth money too.

More practically what I see near me, is IF someone is willing to take the time to remove all the parts and clean the case out, they can resell the case (and PSU if working) for $20 or less.

The motherboard is a different story, if the caps are replaced it varies what one might sell for on ebay, some people will pay too much for something just to save more than buying a whole new system.

Let me give some perspective based on US pricing "sales"/deals.

Modern current generation sale prices in USD:

8GB DDR3 $50
Dual core CPU $50
HDD (an anomaly since Thailand flooding so I quote pre-flooding prices) 1TB $45
Motherboard (low end, low feature OEM type) $45
Case $30
PSU $20
DVDRW $20
-----

$260 for a faster, more capable/modern build that is new with parts warranties. The system I'm currently typing on is over twice as fast/capacious as the Dells in every way and I'd love to be able to sell it for $300. I'd have to find a sucker to pay $200.

[999999999]

Re: Changing to Polymer Capacitors Help!

To add to my last post, I'm staff at an internet bargain site so I may know of better sale prices than many people, it was just one perspective. The PSU for example, a midgrade unit fit for a low-demand system, on sale and w/rebate but there's also a low of low end junk in that price range, you have to be picky.

[Alup]

Re: Changing to Polymer Capacitors Help!

I know its been awhile since i updated my post but I convinced my company to shell out 33,000 for new optiplex 390's

Thanks for all your help!