14 May
2007
14 May
'07
10:22 p.m.
I'm guessing that old (circa early-70s) electrolytics which have a green cap
at one end and a red cap at the other are polarised and that the green end is
-ve. Can anyone confirm to save me tracing out schematics?
I wouldn't put my life on it, but I am pretty darn sure you're correct.
They're in the power supply of an IME-86s calculator and are decidedly past
their best :-) (At least four of the ten in the PSU are showing signs of major
leakage)
I haev an IME86, and even think I know where it is. If you want me to
look at the caps in my machine, can you give a description as to where
they are. I can then see if mine have other markings.
The rest of the machine *looks* healthy enough; once I've replaced the
electrolytics is there any good reason not to slowly run the system up on a
variac (rather than giving it full AC from the start)?
I've never foudn a variac does any good at all (and in the case of
SMPSUs, which approximate a constant power load, they can actually do a
lot of harm).
What I do is check the earth wire continuity (at a test current at least
twice the fuse rating to pick up marginal connections), then 'Megger' the
transformer and amins side stuff. If that's OK, I am pretty confident
it's not going to harm me. I then power it up with a suitable light bulb
in series with the mains as a current limiter. That will protect things
in the eventt of a major short in the PSU section (for example, if a
rectifier has shorted, that light bulb will protect the trasnfroemr)
-tony