[TenTec] Fragile Radios

[Dr. Gerald N. Johnson]

On Wed, 2007-09-12 at 23:20 -0500, Steve Berg wrote:
> I have a really nice Omni V and have never been able to make much use of 
> the audio filter in the rig. Instead, I use a Autek external filter to 
> good effect.  Does anyone here know if this could be a problem with 
> older electrolytic caps? Since I plan to use this rig for many more 
> years, would it be advisable to recap it like Joe has suggested?  I also 
> have done this many times with my older boat anchor radios.
> 
> Steve WA9JML
> 
Some varieties of miniature electrolytics have a high power factor when
new and fresh. Many were not well made. There was once a period when
nearly every computer mother board had bad capacitors because some
Chinese lowest price maker didn't make the right and they couldn't stand
rated operating voltage or even a fraction of it. But tended to short
and eject their guts.

I've been testing miniature electrolytics for several years with a
modified Heathkit capacitor tester that has power factor on two of the
capacitance ranges. I've found no used miniature electrolytics with good
power factor and the most commonly available new ones not better. The
low ESR and high temperature range capacitors measure significantly
better.

I'm of the opinion that in time, if not now, many solid state vintage
radios need every miniature electrolytic replaced, just like we replace
molded oiled paper capacitors for their inherent leakage. And like those
oiled papers, I don't think its worth the bother to test them, just
replace them. Even the low ESR parts aren't expensive.

-- 
73, Jerry, K0CQ,
All content copyright Dr. Gerald N. Johnson, electrical engineer