Dear Friends.

Last weekend whilst I was repairing a switchmode power supply, I had to look through my stock of caps to find replacements for the faulty caps.

I found a suitable replacement for one of the electrolytic caps, but its figures on my capacitor tester were worse than for the one I had removed. I looked at the new cap and found that it had blown the vent at the top of the cap. This cap had never been fitted before, nor used to temporally bridge a suspect bad cap. This I can tell from the cap's leads.

Also, and this is disturbing, I found that while I was searching through my supply of electros, I came across some caps that have a plastic insulator placed over the safety vent.

Blocking this safety vent makes this cap the equivalent of a pipe bomb.
I have heard the extreme sound of a small electro going off, and have seen the damage of it's destruction. Imagine the damage to be caused by one of these monsters rated at 470MFD 350V !

Normally, I would shy away from anything that might be considered as possibly slanderous, but as this is a safety issue, I will add the following information,

The caps were bought from WES Components, and are of the Jamicon brand. Which I have considered (a trusted brand).

I implore all members to see whether or not they have in their possession one of these possibly injurious caps.

I personally, shall cut the shrinkwrap away from around the top of my affected caps and remove the piece of plastic obstructing the safety vent. I shall retain one of the caps, (as is), in case of legal action.

As the photo upload service is not working at the present time, the photographic evidence can not yet be posted. Be assured that your safety is placed ahead of the contrary opinion of others.

The photos will be posted as soon as the photo upload service is available.

Wayne.

G'day Wayne,

Always be sure to send to the address linked from my profile page. It has no limitations on file sizes. The other address you were using does have limitations in place though.

I may be wrong here, but the pressures involved in venting of a cap would also push the plastic insulation out of the way as well. So I don't think you need to remove any of that insulation.

One of the things that must be appreciated with electrolytic's, is that they will loose polarity when stored for long periods and loose polarity. This also happens when the apparatus is not used for long periods.

That is one thing that does encourage them to explode, as they will often present as a short circuit. This is why you never power radio sets that have been sitting for decades. I have seen all of what looked like sealed RB types on a motherboard, with a large amount of their electrolyte on their outside & none seemed to have actually exploded.

The Quality of many new caps leaves a lot to be desired. Some are just cheap & nasty & profit based in their pricing. I have had 450V RB's fail in two years on a rail that never exceeded 250VDC. I have not seen a modern cap that has a surge rating like the old Ducons. I will not use 450V ones on valve radios with rectifiers like 80 / 5Y3 or any other rectifier that produces a surge before heater conduction.

The supplier is of course in denial, after a 500V cap B+ being monitored (always do that on a repaired set, first off) let go before 500V. I put the remaining ones of that batch on a reformer, & am less than impressed with them. I will not buy that brand again, so I voted with my feet & bought the new lot from Savell.


Marc