The AM Forum

Just had lunch with some ham friends - all of us are older hams.

One (who is not a real techie brought in two used can type 20uF 450 volts electrolytic caps. He indicated that they were at least 60 years old and he wanted to get them tested and "reformed"

Another ham took the caps and checked them with a portable meter of some type and proclaimed them "just fine" - no need to reform them.

My comment was "just fine for the trash can". Another friend said to gut them and put a good 105 C cap inside which I agreed with. The ham that "just fine'd" them got really pissed and indicated that they were fine , that his meter showed the ESR was low and even if they failed the radio fuse would save the power transformer.

My comment was "BS"   He got very angry and nearly left.

The guy took the caps home and I think he plans on using them in one of his receivers that has hum.


I really don't understand the belief that 60 year old electrolytic caps are fine and can do no harm. Not at the price of good low ESR 105 degree C caps.



Pat
N4LTA

I'm with you on this Pat.  Old electrolytics will fail, as all of them depend on some sort of liquid/gel dielectric to get the high uF in a smaller package.

The guy with the meter was right, they were good that day.  So are the lightbulbs in your house, but you never know when they will die.

I've seen 80-year oil caps keep on going, the oil must be the magic.

Some big micas (G1-5) can live forever, too.

73DG

True, but it doesn't necessarily mean that all 60 year old electrolytic caps are bad. My Viking II, built in 1954, still has all the original caps and still works fine. My capacitor parts bins have lots of caps that are between 30 and 50 years old. I actually haven't bought any caps for maintenance replacement since the 70's. I have yet to see one fail on me.

Testing an electrolytic capacitor on a portable meter and testing one using near rated voltage are two very different things.

Electronics tinkerers not taking good advice.
Nah. Never happen.

Testing a 450 volt electrolytic with 9 volts or less isn't my idea of a test.

Pat

A variable HV bench supply at home does the cap checking.

In the field, I use an ex-Bell system kick meter.  It does high ohms with a 45-Volt battery and a reversing switch.  Handy & reliable.

73DG

The issue is the money.  Many hams are cheap. Real real real cheap.  They wont spend $2 for a new cap. Instead, They will reuse 60 year old parts and cook the transformer. Then proclaim, "the transformer just up and died".

C

looks like you ran into one of those pompous "know it all" types who can't stand to have his holy word questioned. I always find them at hamfests selling overpriced tube ham gear or CB leenyars.

The cheapest ham I ever met had a Scottish-built transmitter with hinged flip-up covers over the panel meters so they wouldn't get worn out by being looked at too much.

There is no fool like an old fool and unfortunately there are a lot of them still burning out transformers and refusing to take the blame.

The original 200uF 450V Illinois caps in my CE 100V tested fine at 450V but still I replaced them. Those must have cost a lot of $$ in 59.

Maybe some of the less failure prone caps were built with a 5:1 safety factor. ;D   Seriously, what kind of construction / manufacturing design and standard can make a gell last for 50 or 60 years inside of either a rolled rim can or, even worse, a paper shell?  It's a wonder many of these old electrolytics even still work, let alone at elevated voltages.  Perhaps many of the better quality approached oil based viscosity, drying characteristics, etc. of an all oil based capacitor than we realize.

Could research some; perhaps a lot of experimentation was done in WWII of electrolytic gells along with tropical fungicides, high humidity and temperature applications, etc.

So I tend to give smaller, no hum transformer equipment the benefit of doubt ,particularly if newer, say a Drake SP R4, vs. an older transmitter with larger consequences of capacitor failure.

I have a fairly recent model  table radio that I find hums, ever more loudly now,  even when "off"' .  --obviously the darn thing has cheap filter caps that are on the wrong side of the switch and never see any rest.

105c or not...  What will our replacements look like in 60'years?  The moral, I guess, is to replace electrolytics every 25 years or so if  there's any doubt, bad model history and stuff.

Well,

I really don't feel much better. I got a call this morning informing me that the weekly lunch was ending because "I talked down" to the person who tested the capacitor. Been doing the lunch for 6-7 years.

I probably did get more vocal than I should have. When it was said that the fuse would protect the power transformer I did say BS (I was accused of cussing and talking down)

I am getting do old for this crap (or maybe us older guys are starting to act like childeren).


Pat
N4LTA

Yep, the only reasonable test for any cap is at voltage... the cap checker is a good idea, but it only tells part of the story.

As far as the guys quitting the lunch? Ha ha. Good fellahs, eh?

If any of them are actually your friends, I'd call them up and invite them out to lunch.
An apology to the fellow with too much ego and thin skin would probably help, even though you are technically right. Personally I hate this sort of situation, but in my geezerdom I've been trying to forget about being "right" and try to let people go their own way even it means they flounder or make big mistakes. I mean it is cool to be a guru and and 'expert" but unless you naturally have that magic "guru" attraction power, forget it. Any attempts at it will be met with anger, resistance and worse.

Thank you, this has been a message from the Council Respecting Amateur Participation, a privately funded amateur radio service.

                     _-_-bear

Show up as normal. They will all be there. 

Ham radio is no place for thin skins and tender egos....

I will have to agree with Pat.  If you've never had an old electrolytic explode on you, maybe you don't worry so much about it.  They make a mess.

As far as the 'experts':  That is like trying to convince an electrician who always works AC [and is a self-proclaimed expert on all that uses electrons to do work] that in the DC color code  black is not hot and red is not second hot wire.

Mitch,

I did the converse of that. When I was in high school, I was always fooling around with tubes and electronics. My parents had a cabin at a lake and I was asked to put in some outdoor lights to light a path to the dock. I dug a ditch and put the wire into the ground and wired up three lights. Everyone thought they were great.

I touched one of the lights while wet and barefoot a few weeks later and learned the hard way that black is the "hot" wire with AC.

Pat

I personally like to sleep at night and also dislike having to hold my breath every time my HQ-140 is truned on. That's why I replaced all the caps when I restored the receiver two years ago.

Considering inflation (denied by most government officials) today's cost for a new multisection electrolytic from AES is roughly equivalent to the cost of a new Mallory FP back when the receiver was introduced.

Medical terminology for taking a chance on an ancient capacitor would be "Watchful Waiting." That's great until the doctor frowns and says, "Uh-oh. We waited too long."

Pat, stand your ground. If a know-nothing (why did he ask the question in the first place?) wants to believe what another know-nothing tells him, that's his problem. The fact that they can't accept  well founded contrary advice without getting into a hissy fit tells something about their character. They can disagree if they are that stubborn, but to stop seeing you is nothing more than childish behavior, not to mention contrary to the ham spirit that existed at one time.

Bob

Pat, leave the idiots to stew in there own excrement and invite the better of the group to lunch or get some new friends...same day, time and place. Maybe explain in detail to the new group the reasoning behind your comments and it will eventually filter down.

Life is too short to tolerate fools.

Carl

I agree. Maybe only you were told that it's off. It seems petty and all blown out of proportion. Show up and have lunch. If they are not there, then it's not your problem. If they are there, then someone's caught in a public lie. Better to get it in the open and go forward, with or without whomever can't deal with normal life.

talking down to.. People who openly complain about being talked down to often have a character flaw of a superior opinion of themselves. They should correct that appearance. Whether they truly change or just give it lip service is immaterial to getting along.

High voltage is something not to be trifled with.  An electrolytic capacitor explosion will drive this point home very well [not to mention accidentally grabbing hold of said voltage].

In my experience, "know-it-alls" typically have thin skin.  Which is sad, because some of them could go from "bozo" to "knowledgeable" with little additional effort, and be the better for it.  As Mr. Twain so eloquently said, "It ain't what you don't know that gets you into trouble. It's what you know for sure that just ain't so."

Pat, I leave it to you to decide about the lunch.  But it is a shame to see a good opportunity for fellowship be cast aside.  Even having just turned 49, I think I can say with all conviction, "we ain't gettin' any younger."

 ;)

Pat, start your own tradition.  Invite the fellows you enjoy being with to lunch again, same time, same place.   Life is too short to spend dealing with angry people.

I replace capacitors.  It's cheap insurance.  I had a cap in a Collins spew electrolytic on me like a volcano once, because the owner didn't replace it.  Fun.