Re: strange electrical issue - anyone have any knowledge of what to do.


Christopher Erickson
 

I have to wonder if the Pyramid power supplies that have failed in the past couple of years that we have heard about so far, are specifically because of this vibration-caused, failed cap issue.
 
It is the type of delayed-failure that would not be detected by routine assembly-line QC testing.
 
It might be interesting if people who owned these power supplies would all open the cases and look for the potting compound around their caps and note the approximate date when they received their power supplies.
 
 
-Christopher Erickson
Observatory engineer
Summit Kinetics
Waikoloa, HI 96738
www.summitkinetics.com
 



From: ap-gto@... [mailto:ap-gto@...]
Sent: Saturday, October 21, 2017 10:19 AM
To: ap-gto@...
Subject: RE: [ap-gto] strange electrical issue - anyone have any knowledge of what to do.

I noticed that too but wasn’t sure what it was. I just re-read the original post and this is the good working board. So looking visually wouldn’t have done anything anyway.

But I did learn something today…I’ll mark the calander……if I can find it….

 

-Steve

 

 

From: ap-gto@... [mailto:ap-gto@...]
Sent: Saturday, October 21, 2017 4:05 PM
To: ap-gto@...
Subject: RE: [ap-gto] strange electrical issue - anyone have any knowledge of what to do.

 

 

That is definitely a hard potting compound and not leakage from the caps.
It was manually applied after the board was assembled. You can see where a
tiny bit was dribbled on the left top of the 330 Ohm resistor
(orange-orange-brown-gold bands) just beneath and to the left side of the
three caps.

Electrolytic caps are dry and don't have any fluids or glues inside. They
are basically two long, thin conductive plates with a couple of insulator
sheets between them that has been wrapped up tight like a roll of toilet
paper and then stuffed into a protective can with a rubber plug. The cross
pattern on the top of the cans are designed to rupture at low pressure,
allowing a failing cap to vent hot gasses before they build up to explosive
pressure levels.

The fact that those three caps are potted tells me that at one point Pyramid
started having problems with excessive cap failures in their power supplies
due to transformer vibration coupling.

I'll bet there was a lot of angst at Pyramid before they finally figured out
that problem and also an expedient fix.

At some point they must have switched suppliers of the caps and the new caps
were more fragile. That's quite common with counterfeit parts, although
that doesn't definitively mean the caps are counterfeits.

Personally I would have instead decided it was an excellent excuse to bite
the bullet and upgrade the whole power supply design with more modern
technology and components.

And also time to start only buying electronic components from distributors
that have implemented certified component programs and associated
guarantees.

-Christopher Erickson
Observatory engineer
Summit Kinetics
Waikoloa, HI 96738
www.summitkinetics.com

-----Original Message-----
From: ap-gto@... [mailto:ap-gto@...]
Sent: Saturday, October 21, 2017 9:02 AM
To: ap-gto@...
Subject: RE: [ap-gto] strange electrical issue - anyone have any knowledge
of what to do.

The 4700mf 25 volt cap looks like to it has leaked out badly along with 2
other caps nearby C3

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