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Alex

Quadra 950 Capacitor burned (C26)

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Dear Members

 

Recently I noticed my Quadra 950 not responding correctly to power ups, it was somewhat intermittent - the PSU appears to work as expected however. I took it apart and pulled the logic board out and noticed that a tantalum capacitor had burned up, it had some white powdery substance on top and appeared cracked in half. I carefully cleaned the area in and around the cap and while doing so it literally fell apart. The pad came loose either before or during cleanup but continuity is good — for now I applied a drop of solder until someone here can guide me on which capacitor to buy and where.

 

Can someone give me a link to a source where I can buy the same capacitor? I was unable to read anything off the capacitor due to the damage.

 

PS, I know the pad to the right looks nasty but it had come loose but continuity is fine.

 

Thanks so much, please refer to the images for guidance on where it is on the board.

 

Kind regards

—Alex 

IMG_4668.jpeg

IMG_4667.JPG

IMG_4666.JPG

IMG_4665.JPG

Edited by Alex
grammar

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Thanks very much!

 

I think you are right but admittedly it is a guess but a good one.

 

68kmla was down last night so to my own devices I found a high res image of the 950 logic board, you may have posted the same one and yes I think your evaluation is correct.

 

 

Screen Shot 2018-01-09 at 9.37.18 AM.png

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Hi Bolle

 

How would I check if the voltage regulator is ok? Can I check with a multimeter? How would I do that?

 

Also, where can I find the part U32 as in the attached image?

 

 

IMG_1216.png

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23 hours ago, AlpineRaven said:

Its 47uf 6.3v

Cheers

AP

AlpineRaven, I contacted Mouser with photos of the part but they asked for more photos. My question to you is how do you know the values of this tantalum capacitor? I want to be sure you are absolutely correct before I update mouser with the values you replied with. Thanks very much!

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Your picture more looks like 10uF, 16V to me.

This would make more sense as the caps are connected to the input of the voltage regulator, which is most likely 12V and not 5V.

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2 hours ago, Bolle said:

Your picture more looks like 10uF, 16V to me.

This would make more sense as the caps are connected to the input of the voltage regulator, which is most likely 12V and not 5V.

Very interesting. Here are some other shots of the same component from other angles which from their respective vantage points would appear to support a 16V value.

10uF, 16V is convincing to me in terms of what I can see printed on the tantalum cap. Bolle, what do you suspect the 2 on the positive side refers to, a manufacturer or something other?

 

Thanks very your thoughtful observations.

IMG_1225.jpg

IMG_1223.jpg

IMG_1226.jpg

IMG_1227.jpg

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2 hours ago, Bolle said:

 

This would make more sense as the caps are connected to the input of the voltage regulator, which is most likely 12V and not 5V.

Attached is an image highlighting the voltage regulator markings.

Screen Shot 2018-01-11 at 2.17.02 AM.png

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Yes, but the capacitors are connected to the input of the regulator, so they are running with more than 5V - probably 12V. That is why 6.3V capacitors would not make sense right there.

The "2" on the capacitor does not matter. It probably won't even matter what exact value you replace it with as long as the voltage is high enough.

Edited by Bolle

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11 minutes ago, Bolle said:

Yes, but the capacitors are connected to the input of the regulator, so they are running with more than 5V - probably 12V. That is why 6.3V capacitors would not make sense right there.

The "2" on the capacitor does not matter. It probably won't even matter what exact value you replace it with as long as the voltage is high enough.

Bolle, could you help me out. Still no answer from mouser.

If you have time, would you be so kind to provide links for the cap and regulator from mouser or otherwise? I have so little experience with finding the parts successfully … all I want are good quality components. I would be so grateful, it's that last mile I need to place a successful order.

 

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8 hours ago, Bolle said:

Yes, but the capacitors are connected to the input of the regulator, so they are running with more than 5V - probably 12V. That is why 6.3V capacitors would not make sense right there.

The "2" on the capacitor does not matter. It probably won't even matter what exact value you replace it with as long as the voltage is high enough.

Guys

 

really need to be sure that the courtesy recommendations you have made are correct. Could I please ask you to confirm if the evaluation on parts needed are as accurate as they can be with the knowledge I provided? Unfortunately I don't have the expertise to go forward on my own. If possible please provide me links for parts, I will order, install them and report back. I would be incredibly grateful.

 

Below is the response from mouser.com

 

Dear Alex,

 

thank you for your email. We tried to recognize requested parts by provided pictures and unfortunately we cannot recognize any specific capacitor.

Therefore we cannot place an order for you.

We kindly ask you to have a look on the link below and choose one of ours capacitors :

 

https://eu.mouser.com/search/refine.aspx?N=254295

 

If you would interested, please, let us know.

Thank you.

Best regards,

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It appears to me to be a Vishay 10uf 16v tantalum cap. 10uf 16v is a common Mac logic board cap value.

 

It's a little worrying to see all these recent spectacular tantalum failures. The meme of "tantalum is good forever" isn't holding up.

 

Edited by IIfx

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On 2018-01-11 at 4:53 AM, Alex said:

Guys

 

really need to be sure that the courtesy recommendations you have made are correct. Could I please ask you to confirm if the evaluation on parts needed are as accurate as they can be with the knowledge I provided? Unfortunately I don't have the expertise to go forward on my own. If possible please provide me links for parts, I will order, install them and report back. I would be incredibly grateful.

 

Below is the response from mouser.com

 

Dear Alex,

 

thank you for your email. We tried to recognize requested parts by provided pictures and unfortunately we cannot recognize any specific capacitor.

Therefore we cannot place an order for you.

We kindly ask you to have a look on the link below and choose one of ours capacitors :

 

https://eu.mouser.com/search/refine.aspx?N=254295

 

If you would interested, please, let us know.

Thank you.

Best regards,

Really, all you need to do is buy any 10μF, 16V (sometimes written 10uF, 16v, with a “u” rather than the Greek letter “mu,” μ) tantalum capacitor (the little rectangular ones, generally yellow these days) from any source whatsoever. If mouser won’t cooperate, there are bazillions on eBay available for peanuts, because they are very common.

 

If bought at that specific rating, it will fit fine and (assuming all else in the Q950 is good) it will work.

 

You might as well buy a small lot of them, in fact, if you plan to keep this hobby up, as they will come  in handy when working on old logic boards.

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Thanks to everyone who was so generous with their replies. I sent Bolle a direct message and was so kind to send me a direct link to the part on a large German parts distributor.

 

Many thanks to all for the support.

 

 

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I don't know if anyone is still paying attention to this post but I wanted to ask, what is ESR?

 

I found the Vishay IIfx mentioned, there are four 10uf 16V Vishay Tantalum Capacitors but why four, I see the ESR values that differ.

 

.8

2

1.7

3.4

 

I have heard of ESR meters.

 

To jump start this OT part of the discussion, if it continues I found the following:

 

The ESR rating of a capacitor is a rating of quality. A theoretically perfect capacitor would be lossless and have an ESR of zero. It would have no in-phase AC resistance. We live in the real world and all capacitors have some amount of ESR 

 

Here is the link to the quote above.

 

Now, I know that this might be picking teeth here but this stuff is really interesting to me and I will have to read more on this but if any want to indulge me please do, I would love to get your take.

 

By the way, the fourth cap is 10 volts, I know I shouldn't buy that one. I won't be buying from mouser anyway but still …

Screen Shot 2018-01-14 at 5.09.28 PM.png

Edited by Alex

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I have a spare Q950 with the same capacitor burned out. I replaced it and it burned out again almost immediately. I checked voltages with the capacitor removed and nothing exceeded 12v, so I don't know why it kept dying. Just for kicks I cleaned it up, reassembled and attempted to boot the machine and it turned on. It booted System 7.5 from a floppy, loaded the desktop, had a good display, produced audio, etc. I didn't check the Ethernet or serial ports but nothing seemed affected. It soft-powered on and then soft-powered off. No idea what that cap actually does other than explode.

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