Has he checked/replaced the diode? maybe the cap is
seeing a bit of AC due to diode leakage or something.
Mark WB8JKR
On Sat, 26 Dec 1998 19:50:02 +0800 Alek Petkovic <vk6apk@eon.net.au>
writes:
>
>Hi All,
> A friend of mine in Virginia is having the following
>nightmare
>with his SB220. Can anybody help?
>
>I have copied and pasted his e-mail and deleted all the expletives. I
>think. If there's still one in there, please forgive me and him. It's
>Christmas.
>
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> Sat, 26 Dec 1998 06:29:05 -0500 (EST)
>Message-ID: <3684C91C.6B92@erols.com>
To: <amps@contesting.com>
>Date: Sat, 26 Dec 1998 06:31:40 -0500
>From: Bellford Kellem <belkel@erols.com>
>Reply-To: belkel@erols.com
>X-Mailer: Mozilla 3.01C-KC032698 (Win95; I)
>MIME-Version: 1.0
>To: vk6apk@eon.net.au
>CC: w4ubc@visi.net
>Subject: Help
>Content-Type: text/plain; charset=us-ascii
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>
>Alek,
>For 40 ------------ years of my ------- life I was a practicing
>electronic
>engineer. I have designed and built every kind of power supply you can
>imagine from little 5 volt units to 30kv radar power supplies. Half
>wave, full wave , bridge, 3 phase, etc. I have installed 1000s of
>filter
>capacitors with never a ------- problem.
>
>My SB220 contains a small transformer with two windings. One winding
>supplies the filament voltage for the 3-500zs and the other supplies
>bias and relay voltage at 120volts. One side of the relay coil is
>connected to this little half wave supply. The other side of the relay
>coil goes a jack on the back of the linear. When this jack is grounded
>it closes the relay and the linear goes into the transmit. From the
>banded end of the diode rectifier, a 20ufd, 160 volt electrolytic
>capacitor is connected from this point to ground. Without this
>capacitor the relay will not close. It just chatters from the
>pulsating
>dc voltage. Just what you'd expect.
>
>I have gone through at least 10 capacitors, and each one explodes
>after
>a short time. Six of them were supposedly new stock. Last week I took
>one of these "new caspacitors" and preconditioned it by putting it
>across a dc supply which I increased from 20volts to 125 volts 20
>volts
>at a step, leaving it for 2hours at each step. I installed this
>capacitor yesterday morning and spent most of the day dxing on twenty
>meters. I gave that ------- linear a workout like it ain't had in 25
>years. Got reports from all over the world from S9 to "loudest signal
>on
>the band". I thought I had it made when at 3:45 local time that
>capacitor let go like a shot gun blast. Blew pieces all over the
>-------
>living room.
>
>I am at my wits end. You mentioned you were "dropping a couple in the
>mail" If you have done so, bless you. If you have not get your -------
>---
>--- to the sodding post office and do so. I'll pay, whatever it
>cost. I'm ------!
>73, de KC4DWI
>
>
>Any Ideas?
>
>73 de Alek, VK6APK.
>
>--
>FAQ on WWW: http://www.contesting.com/ampfaq.html
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>Administrative requests: amps-REQUEST@contesting.com
>Problems: owner-amps@contesting.com
>Search: http://www.contesting.com/km9p/search.htm
>
>
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