Fw: Electrolytics "blow up"

[talen]

I see from one of the later notes that you found the problem to be
a defective resistor which increased the voltage applied to above
the rated levels, however, since this was ready to send, it may be
usefull to others.

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First thing to do (assuming they are the correct voltage or higher) is
to bring "new" electrolytics up slowly. You can do this with a variac
on the HW-16 or connect a variable DC power supply to the electrolytic
and take 5-10 minutes to bring them up to rated voltage a little at a time.
You only have to do this the first time. Once they are damaged internally
and develop a current path, they eventually overheat and go.

You can also get a capacitor checker to check for leakage and to
slowly bring up electrolytics since they test at rated voltage (switch
selectable). Again bring them up slowly the first time. One of my cap
checkers is a Heath IT-28.....works great.

Since these checkers are current limited (good idea) you can see what
happens. I've connected a very old "new" 450V electrolytic across the
tester and it will indicate "high leakage" at 100V, then the eye slowly
opens up, then it indicates "high leakage" at 200V, then the eye opens
up, etc. I do this several times and finally, after fully discharging the
capacitor, the eye opens up quickly at 450V. You can just imagine what
would happen if full voltage at high current was applied immediately as in
your HW-16.

73s  Kees K5BCQ

----------
From: Bill and Edna <Eshukis at HOME.COM>
To: HEATH at LISTSERV.TEMPE.GOV
Subject: Re: Electrolytics "blow up"
Date: Sunday, November 28, 1999 12:55 AM

Hmmm.. Brings back a recent memory.  I replaced two High Voltage Caps in
the HW-16.  They
were about 3/4 inch diameter..rated at 40uFd and 350V.  They Blew up in
about 30 seconds.
How can I tell a High Resistance from a Low Resistance Electrolytic?

I'm still determined to get that Rig on the air!!

Bill
K3OBB

Dave Edwards wrote:

> You may be searching forever for a replacement.
> Its just an HW16.... Get some elecrolytics, and mount them under the
> chassis.
> Then you can use it with no fear of high resistance caps to blow up.
> ...Dave
> -----Original Message-----
> From: Mark V. Johnson VE3DJU <mjohnson at CA.IBM.COM>
> To: HEATH at LISTSERV.TEMPE.GOV <HEATH at LISTSERV.TEMPE.GOV>
> Date: Saturday, November 27, 1999 4:32 PM
> Subject: Electrolytics

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