Harry Dalek wrote:Perhaps there should be a time where you fire up your old gear just to keep it working.
Steve Anderson wrote:It's no bad idea, it helps keep the electrolytic caps 'healthy'. Even brand new ones from a supplier can fail if they've been sat on their shelves for years (it happens). Luckily I have a Variac, so I can wind up the voltage gently and that gives caps that haven't seen any voltage in a long time a chance to 're-form', Do a search on 're-forming capacitors', it mainly applies to electrolytic caps. There are quite a few sites concerning this.
I build things for a variety of reasons, some end up in almost daily use (e.g. a bench power supply), others are built just to create an item to be published somewhere. Once they appear in print their job is done and usually end up gathering dust somewhere. That 1" CRT item is a good example. I did it simply for the novelty of finding a use for the CRT. It hasn't been powered up in over a decade.
Steve Anderson wrote:My experience tells me that usually the lower voltage elects are OK unused for a long period, but the higher voltage caps (say 200V-plus) can be troublesome. It is worth working out a simple arrangement to 're-form' them. A Variac is obviously the simplest arrangement, in the absence of that a tapped auto-transformer, but they're quite rare these days. The best alternative is a variable high-voltage DC power supply with some form of current limiting. Even if only can supply a few mA, that's enough....or should be.
For this purpose a simple audio power amplifier feeding a reverse-wired transformer should do the trick. It doesn't need to be high-powered, say a TDA2030/TDA2050 feeding a small 12VA 12V transformer in reverse...rectify the output, done. Should be be good for up to 400V caps...few these days rated for more than 450V DC...
Steve A.
Steve Anderson wrote:Variacs are still made but they are expensive, though very useful when you need one. I bought one (new) in Singapore about 20 years ago, a smaller 300W version, which is enough for the stuff I deal with. 0-260V. I can't recall what it cost, it was some 20 years ago, so irrelevant today.
That Variac, still in daily use, has gathered a lot of dust.....note the binding posts/terminals, not a proper plug/socket arrangement...guess where it was made.....a clue - I had to add an earth terminal/connection to earth the metal case, there wasn't one fitted and originally it only had a two-core power cable...
Steve A.
Steve Anderson wrote:I'm a little bit concerned about "Lab Guy"...he hasn't posted on his channel in around three months, rather unusual for him...also several of my postings above are also of similar age...
Steve Anderson wrote:Well, let's hope that's the case and not something that's really bad news...
Steve A.
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