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Joined: Feb 2005
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Hi All, Recently experienced with one unit during charging to 360J, that the main energy storage capacitor made a severe crackling noise, on further investigation we noticed the capacitor was leaking around its connection terminals. Thought this to be an isolated problem until we examined another two units with leaking capacitors but no crackling sounds during charging. Yes, these devices are out of support so no spares from Philips, currently investigating OEM supply of capacitor for short term fix until replacement defib program can be sorted.
Expensive solution whichever route is taken!
Wondered whether anyone else experienced leaking or crackling main energy delivery capacitors?


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Hi Font,
I had this problem with a Codemaster at the previous hospital I worked at in 2004. When charging to 360J the unit used to crack & bang quite violently, but still worked OK! (Although it was scary charging the unit up, especially with the case open!!)
A new cap was ordered at around £840 (if I remember rightly), but I started my new job before it arrived so I never got to finish the repair myself.
Another observation was the resistor used to dump the charge. A colleague had, during testing, repeatedly charged to 360J & then selected a lower setting, causing the resistor to burn the top layer of the pcb off!

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Hello Font,

We have started to experience this crackling from the HV capacitor over the last 6 months.

We see it happening when performing the automatic disarm test where the defib is in the charged state for around 30 secs before bleeding off the energy. We have started to inspect the capacitor terminals but have yet to experience any electrolyte leakage.

We have contacted Philips who confirm the capacitor, this is arkward as they no longer supply the part.

The device itself is recommended as a 7 yesr lifespan and i assume as you are experiencing this problem all of your units are over that age. The parts in the patient circuit im pretty sure are limited lifespan so the HV capacitor experiencing this problem is expected after 7 years.

I think that HV electrolytic capacitors have a 10-20 year lifespan before they start to dry out.

If like us you have no money to spend on new defibrillators this year will cause somewhat of a problem.

As long as the defib passes all tests i have been informed that it is ok to go back into service, but have also been recommended that these models should be RFS now.

At the moment if our codemaster passes all tests, with no evident leakage from the HV capacitor and if the popping is only slight, we are logging this information and returning the device back into service.

How much popping from the capacitor do you allow before you decide to remove the defib from service? How can you quantify that?

We cant just remove all of our defibs without replacing them....can we?

If you reach a solution Font then let us know.




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I don't think 360 joules gets used too often these days, with the change in protocols etc. If the unit works alright at 200 joules and will deliver during test at 360 then I would do as you say, note it down and continue to use it.
I used to have a similar problem with th old Marquette 900 series defibs. They were used in this condition for many years without any problems.

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Rick and everyone,
The change of protocols only applies to biphasic defibs.
"The recommended initial energy for biphasic defibrillators is
150-200 J. Give second and subsequent shocks at 150-360 J.
• The recommended energy when using a monophasic defibrillator is
360 J for both the initial and subsequent shocks." from the ASL guidelines of the Resuscitation Council.
So the 360J setting will be used.

Mark,
Is putting a defib back in to use with a known potential fault safe? What happens if the capacitor fails when it is used for real, rather than in a test?
Surely this problem should be raised at a high level, and loud and soon. Does your department want to face a corronor and say that you knew about the problem and ignored it. If the hospital decides not to renew the defibs then that is their problem not yours.

Robert


My spelling is not bad. I am typing this on a Medigenic keyboard and I blame that for all my typos.
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Just some info,

the codemasters are monophasic the guidelines (2005) state that 360j is the prefered energy for defibrillation using a monophasic machine in cardiac arrest
Algorythm link below.
http://www.resus.org.uk/pages/alsalgo.pdf

200j is used occasionally in emergencies where the operator isn't sure whether the machine is biphasic or monophasic.
After risk assessment we are planning to replace our codemasters with biphasic technology as the codemasters are starting to fail and are no longer supported by phillips

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Sorry RoJo didn't see your post

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We come across it with our Lifepak 9s.

If I remember rightly, and it was some time ago, we were told it was due to small internal break down of the capacitor and the "cracking" was due to arcing between the plates inside the capacitor. We were lead to understand that the capacitor "self- healed" and so long as the charge time was within spec to continue to use the defib. This phenomenon was due to the capacitor not being fully "exercised" on a regular basis - typical of a 200J regime where the charging voltage is somewhere around 50% of that required for 360J.

You notice the cracking normally during PPM when you take the defib to 360J.

We used to advise our nursing staff to perform the routine at 360J for just this reason - and you could tell who took notice of your instruction by listening to the cap during charging.

As I said, it's some while since I did the LP 9 course and if anyone has any different info I'd be pleased to see it.

Brian


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The problem is due to breakdown of the dielectric between the capacitor plates. The plates are self-healing, meaning plate damage is limited, but this means there's a gradual loss in the surface area of the energy storage capacitor plates over time.

Ultimately this results in a loss in capacitance. As the capacitor ages then the breakdown gets worse and may be exacerbated by the fact that, for a given delivered energy, when the defibrillator is in calibration, the actual voltage across the storage capacitor may increase slighty (Q=CxV).

This further encourages breakdown. As the rate of dielectric breakdown increases this popping or crackling sound can be heard as energy being dissipated in the capacitor, resulting in increased electrical leakage from the fully charged capacitor.

I think age, temperature, cycling and electrical stresses, i.e. rate of charge, P.D. across the capacitor and number of full-charge cycles, contribute to this problem.

In practice I've had to change capacitors that fail the energy discharge test (360J to 1J in less than 20s) because the capacitor has gone out of tolerance (measurement has confirmed this and changing the capacitor has solved the problem).
The sounds of discharge inside the capacitor at 300J-360J can get that bad that operators think it's the mains socket is arcing, so they report the machine faulty despite it being functionally OK and operating within tolerances.

We have about 40 LP9 defibillators left in our hospital now and about 20 faulty energy storage capacitors on a shelf yet to be disposed of responsibly. Our LP9s are about 14 years old on average though so we've had reliable service out of them.

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"Our LP9s are about 14 years old on average though so we've had reliable service out of them."
Glad to see Colin Friend,s astuteness paid off then Richard

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