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To replace or not to replace?
- Thread starter Staybolt
- Start date
A solder sucker for the larger ones. Wick for the tight spaces.
If you are going to do a LOT of it.... (like... you enjoy restoring for a hobby OR vocation) this is the one I bought. Literally.... once you located the cap on the foil side of the board, about 5 hot seconds... and it is out. Just about turns it into a cap per 30-60 seconds. And doesn't damage the board if you are careful.
https://www.parts-express.com/stahl...-digital-solder-and-desolder-station--374-400
https://www.parts-express.com/stahl...-digital-solder-and-desolder-station--374-400
Electrolytic capacitors in your radio have a lifespan of approx. 10 years. If they are older than 10 years ( like in your older CB radio's from the 80's-90's).....replace them all.
What many people don't realize is that capacitors have an infantile failure rate. A new cap can fail with a bang. An older well tested cap that isn't broke can out last a brand new cap. I have heard this theory that the capacitors can go dry. If it was not damaged during the install it should be fine.
Biggest source of failure in aluminum electrolytic caps is the rubber plug seal at the end of the aluminum can enclosing it.
The water-based chemistry inside the cap can last for a long time. A capacitor that has been on the shelf for 40 years in a proverbial cool,dry place may check perfectly okay. And if you see a bulge under the rubber, that's the pressure release valve. That part is already going bad. Yes, they fail from age even when not used. Eventually.
Heat is the enemy. Both from the surrounding circuitry and from heat the capacitor releases inside. The rubber end-plug hardens and shrinks. Eventually the seal is broken. The water-based chemistry inside literally dries up and the part breaks down.
Mileage and age both.
73
The water-based chemistry inside the cap can last for a long time. A capacitor that has been on the shelf for 40 years in a proverbial cool,dry place may check perfectly okay. And if you see a bulge under the rubber, that's the pressure release valve. That part is already going bad. Yes, they fail from age even when not used. Eventually.
Heat is the enemy. Both from the surrounding circuitry and from heat the capacitor releases inside. The rubber end-plug hardens and shrinks. Eventually the seal is broken. The water-based chemistry inside literally dries up and the part breaks down.
Mileage and age both.
73
I have never seen a water based capacitor. I have seen oil based capacitors by the thousands. Water, even distilled water will cause corrosion.
I believe the most common electrolyte is Mineral Oil.
I believe the most common electrolyte is Mineral Oil.
One hour?!? Man, that is pretty good! Takes me about three hours at a leisurely pace to do a SSB radio; of course they have far more caps in them than an AM/only radio.
Back to the old question: why replace caps?
Recently I purchased a computer sound system w/subwoofer and built-n amp from Goodwill for only $4. Because it was left on all of the time by the previous owner, it had failed. Thing is, it isn't that old and this model/make is still in production and on the market. What failed? The caps. Had to change ALL of them (used good caps this time around BTW); and then it worked.
Now, they were using cheap caps in that amp. CB radios are built at a price point (read 'cheaply'). They are at risk based upon the fact that the original caps were not premium caps to begin with - and chances are - they are very old. That is two strikes against them; and those facts are irrefutable.
Sure, you can say that a low level tech would replace all caps rather than just replace them as they go out. But leaving old caps in the radio can also impair its performance. Sometimes without notice, or sometimes it is all too obvious.
If it is an old classic CB radio, then give it and yourself a break and replace them and then go on to enjoy that great old radio as it was designed to be operated . . .
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Some say if I ain't broke don't fix it. Problem with caps is they do have an expected life span. If a piece of equipment is a certain age, and has reached the point where capacitors could possibly, be out of spec change them. It only takes one (capacitor) to have what would be a perfectly good working piece of equipment perform out of whack. Changing the ones that are out of spec and leaving in the other ones in doesn't make sense to me either. If one has reached its lifespan chances are are the ones that check good will also reach, and exceed their lifespan in short time. Why keep opening up a piece of equipment in order to change out 1 capacitor, when chances are anothers going to fail soon? The two technicians I use charge a very fair price for capacitor replacement. It's probably the cheapest part of equipment refurbishment. 73
I have 1976 electrolytic capacitors in my amplifier, working in HV voltage doubler. They keep capacity. Tested. Far better that caps I can buy nowadays.
Do not fox if ain't broken.
Mike
Do not fox if ain't broken.
Mike
That's impressive. But not the case most of the time. Especially with HV caps. If you can check, and know for sure it's ccapacitance is on the money, great. I can't check or change caps. If I send out a vintage piece of equipment the first thing I tell the technician is to replace all capacitors. I won't even suggest that he checked them first. Good or bad their getting replaced. Not to mention the fact that most HV caps can be upgraded. Fewer HV's @ higher capacitance. And their those metal jacket flame proof's as opposed to cardboard. Shipping the equipment is also a factor in my decision to have them replaced. I just don't trust 25+ year old capacitors.