[Johnson] High Voltage Electrolytic Capacitors

[Sherrill Watkins]

Bill: I recently needed two 700 volt rated filter capacitors for the 600+
volt power supply in my Adventurer. I ended up taking the advise of several
helpful people on this board and used two series 400 volt capacitors with
200K ohm equalizing resistors across each capacitor, four total capacitors. I
mounted the new capacitors on terminal strips and the installation looks
"factory" and professional. Someone told me that the old H.V. capacitors were
just two capacitors wrapped in a single container; so I cut open one of the
old capacitors and that is exactly what was inside, two capacitors in series
wrapped in a paper tube. I ordered the new capacitors from Purchase Radio for
low cost and they shipped them the same day and did not charge me any minimum
order. Purchase Radio is great. Also, Leeds Electronics in Brooklyn, NY is
another good source. I have had a very good experience in ordering parts from
those two sources. -73- Sherrill W. k4own. 

-----Original Message-----
From: Bill Evans [mailto:bevans at ebsys.mb.ca] 
Sent: Thursday, January 20, 2005 5:23 PM
To: Johnson at mailman.qth.net
Subject: [Johnson] High Voltage Electrolytic Capacitors


While this problem is not pertinent to Johnson equipment ... yet... I have
several Rangers and the issue is pertinent to all Boatanchor gear.

My Heathkit SB-610 monitor oscilloscope, built in the mid-to-late 1970's,
recently stopped working and I determined that a shorted capacitor in the CRT
HV supply was the culprit. There are two 0.15 micro Ferad tubular
electrolytics, rated at 1600 WVDC, used in a voltage doubler to supply the
monitor CRT. The capacitors are in a plastic package of modest size and
likely cost, at most, a couple of dollars each at the time when I built the
kit.

Searching amongst various parts suppliers, including catalogue houses,
reveals an absence of high voltage tubular electrolytic capacitors. I had
recognized from Electric Radio Magazine that it was tough to find many of the
metal electrolytics for various boatanchor transmitters, but didn't think
that this problem extended to HV electrolytics of all types.

I finally located a manufacturer of plastic tubular capacitors meeting the
requirements, whose Canadian rep quoted me a price of $64.00 for a single
replacement unit.

Having recovered from the shock sufficiently to post this information
request, can someone suggest sources of supply for these types of capacitors,
which were at least as common as vacuum tubes just 20 years ago? Tubes we can
still get.

Bill Evans
VE4UD
Winnipeg, Manitoba, Canada
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