[Johnson] High Voltage Electrolytic Capacitors

[Bill Evans]

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