Strength of capacitor solder connections?

NewBuyer · « **on:** 8 Dec 2006, 09:15 am »

Well here's a very naive question that you definitely won't get everyday.

See the 2 large red vertical capacitors at the top-left of this picture? Each has a pair of leads that are directly soldered into holes in the board, like you see for the horizontal yellow caps. These 2 large red vertical caps do not actually contact the board - instead they sit very slightly above the board, on their leads.

The picture is of a Constantine DAC board (from manufacturer's site). The chassis lid is acrylic, and slightly flexes inward if pressed upon.

In my system, this DAC had another semi-heavy audio component partly resting on top of it, causing the lid to flex inward and, I think, to press down onto these 2 large red caps - thus transferring some top component weight onto the caps themselves.

I fixed this situation immediately after noticing it, but it had already been like this for several weeks.

So, did I likely damage the integrity of the solder-point connections of these caps, from this oversight? The DAC still seems to operate normally, but now I'm worrying about it.

I also noticed these 2 particular caps do wiggle back and forth pretty easily if you gently touch them. Is this normal? The smaller caps on the board are tighter and do not move like that - just the 2 large ones.

Obviously I have no idea how strong such solder-connections normally are, or how much weight they can take. Actually, I don't even know what the symptoms would be (besides a non-functioning unit), if the cap solder-connections were damaged.

So I'm turning to the more tech-savvy and DIY members here, to please receive your advice. Do you think damage here is a likelihood, or am I just worrying about nothing?

Thanks for any/all replies.

StevenACNJ · « **Reply #1 on:** 8 Dec 2006, 09:36 am »

I am no expert, but I do a lot of DIY.

Good solder joints are usually pretty strong. In this situation the cap lead out wires soldered to the boards metal eyelets are going to be a strong joint. However, the eyelet attachment to the board could possible break. I dont know how strong that attachment is.

If the unit is still working then you are probably ok. I would put some blue tack around the base of those two caps to keep them from resonating.

EarWax · « **Reply #2 on:** 8 Dec 2006, 04:43 pm »

Those are the power supply filter capacitors and If they were damaged the unit would not power up. The wiggling you are experiencing is due to the relatively fragile leads on the caps and the fact that the caps are mounted slightly above the board, allowing for some "play" between the board and capacitor. i.e. I think your are OK.

ctviggen · « **Reply #3 on:** 8 Dec 2006, 05:31 pm »

Those are definitely power supply caps, as the diodes and transformer for the "rest" of the power supply are to the right of these caps. (It's interesting that there are no snubbing caps across the diodes.) By the way, those are awfully nice yellow caps. (And I mean this -- I'm not being facetious.)

BobM · « **Reply #4 on:** 8 Dec 2006, 05:39 pm »

You're probably fine with the cap connections. I would follow Steven's advice and tack them down to the board with some Moretite (much cheaper than blue tak and easily purchased in bulk from Home Depot). Just wrap a bit all the way around the base and press it down to the board and the cap sides until it is seated solidly.

While you're in there, do the rest of the caps also and apply some to the chassis to dampen it a bit. Throw a piee over the clock crystal too.

These are all very easy and well worn tweaks.

Enjoy,
Bob

NewBuyer · « **Reply #5 on:** 9 Dec 2006, 11:03 am »

Thank you everyone for these replies, I really appreciate it. Solder connections must be much stronger than I thought? If so, this is good news.

The Blu-Tack (or equivalent) idea is actually new to me, I didn't realize people were putting this stuff inside their audio electronics. Does anybody have a pic of a wrapped capacitor, as described? Does it make a sonic difference, or is it just to stabilize the capacitor/board etc?

avahifi · « **Reply #6 on:** 9 Dec 2006, 12:30 pm »

Two observations:

First, we would normally want any sizeable radial lead capacitors to be firmly seated on a PC card when soldering their leads. Letting them flop back and forth like the sample above will eventually cause a fatigue failure of the joint.

Second, Moretite is definitely not recommended in electrical components, I understand it has an acid component that can slowly corode electrical contacts. Hot melt glue would be a better choice.

Regards,

Frank Van Alstine

NewBuyer · « **Reply #7 on:** 13 Dec 2006, 09:45 pm »

Quote from: avahifi on 9 Dec 2006, 12:30 pm

Two observations:

First, we would normally want any sizeable radial lead capacitors to be firmly seated on a PC card when soldering their leads. Letting them flop back and forth like the sample above will eventually cause a fatigue failure of the joint.

Second, Moretite is definitely not recommended in electrical components, I understand it has an acid component that can slowly corode electrical contacts. Hot melt glue would be a better choice.

Regards,

Frank Van Alstine

Thanks Frank, does the advice about Moretite also apply to Blu-Tack?

avahifi · « **Reply #8 on:** 13 Dec 2006, 10:43 pm »

I am not familiar with Blue-Tac? is there a manufacturer's specification sheet for it. That will normally list toxic and health issues.

Frank Van Alstine

NewBuyer · « **Reply #9 on:** 14 Dec 2006, 06:12 am »

Quote from: avahifi on 13 Dec 2006, 10:43 pm

I am not familiar with Blue-Tac? is there a manufacturer's specification sheet for it. That will normally list toxic and health issues.

Frank Van Alstine

Hi Frank, the only spec sheet (online) I seem to be finding is this one here...

What do you think?

CIAudio · « **Reply #10 on:** 14 Dec 2006, 07:21 am »

As Frank mentioned, the caps should have been firmly seated to the board before soldering. Just the weight of the caps could break the circuit traces in shipping etc.
It seems odd to me that people are still using single-sided PCB's to save a few $$...
Double sided boards are much more reliable because the parts are secured/soldered on both sides and through the board.

I doubt Blu-Tack or Mortite would help much. I know there are adhesives used for gluing the parts to the board before soldering...I've seen this practice in mass market electronics using single-sided PCB's. Older products used something similar to ordinary "contact cement", newer products use a chalky looking paste.

NewBuyer · « **Reply #11 on:** 14 Dec 2006, 11:47 pm »

I just checked out the CIAudio site, wow you have some really nice products.

I think these PCB boards in the Mhdt Labs DAC units may be double-sided (I didn't know there was single vs double sided boards). These DACs do have components soldered to both sides, and the solder connections of top components also is visible from the bottom (like with a computer motherboard for instance). Does this mean double-sided?

jules · « **Reply #12 on:** 15 Dec 2006, 01:00 am »

the photo seems to show that they are single sided but that's not the end of the earth ...

Are you able to check underneath the board? The point Steven made earlier about the attachment of the eyelets to the board could be important if you've subjected the caps to pressure from above. If the movement is very easy, as in not slightly springy, a check under the board could save you some big problems. If things have delaminated, action is vital.

If you can solder, it would be good to do some careful work to make the caps sit closely on the board by re-making the joints

jules

CIAudio · « **Reply #13 on:** 15 Dec 2006, 05:05 am »

Quote

I think these PCB boards in the Mhdt Labs DAC units may be double-sided (I didn't know there was single vs double sided boards). These DACs do have components soldered to both sides, and the solder connections of top components also is visible from the bottom (like with a computer motherboard for instance). Does this mean double-sided?

The photo shows a single-sided board...soldered only on the bottom. Any pressure or excessive movement from a heavy part can push the pads and traces until they come loose and/or break.

A double-sided board has pads on both sides and the holes are plated-thru...when the part is soldered, the solder flows through the hole and solders both sides, forming a rivet-like connection. Double-sided is also used for better layouts and more compact circuitry, but even if it's a simple circuit, it makes sense to use double-sided if only for structural reliability.

Computer boards like you mention are usually 4 layers or more to save space. I don't like multi-layer so much because if an inner layer has a problem, you can't fix it.