the capacitors that look like ceramic ones but have slipery plastic cover are these mylar capacitors. some are also longer oval shaped. will a electrolitic capacitor explode if polarity is wrong or voltage exceded.

 

I don't know about slippery caps, but I can definitely tell you reversing the polarity on an electrolytic could cause it to blow up. Do it to a large filter capacitor and the results are pretty spectacular.

 

the capacitors that look like ceramic ones but have slipery plastic cover are these mylar capacitors. some are also longer oval shaped. will a electrolitic capacitor explode if polarity is wrong or voltage exceded.

They could be mylar if they're old but chances are they're both common Polyester Film Capacitors which have replaced most smallish - mid value caps. They're relaible, inexpensive and spec out pretty good for their price.

Caps in the low pF range are usually still ceramic and most anything above 1 uF is usually an electrolytic.

 

Not everything that looks like a Capacitor is a Capacitor.

Some times you need to see the schematic in order to identify a vaguely marked item.

 

True, the markings should tell all, even pictures would be a great help. For instance the long oval ones could also be tantalums but there should be a + sign on it somewhere. If you're fast enough with an ohmmeter you can sometimes deduce an unknown component but it really pays to spend $20 or so for an inexpensive LC meter to have around. Although I have bench gear I bought one of these because it's a heck of a lot handier to deal with, especially if I need to take it to work for something:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=380024081247

Testing with known values it appears to be pretty darn accurate, the case is thick, switch feels durable too.

 

I wouldn't buy a multimeter unless it had an LC function or it was intended as a cheap extra meters.

After a few accidents I prefer to always use cheap meters for measuring currents.

 

An LC meter is little more than a spot check device for me to catch mismarked items or the value of questionable electrolytics. I generally just order new if I don't have something already in stock. They do come in handy when you have to hand wind RF coils though..

 

i know i usiwaly check the shematic symbols before pulling off the part. if your are wondering how i do this i use a small carved needlenose. this is ok for parts with longer wires. butfor relags and electrolitiscs i desolder those. i have learned to chack thi because i have taken apart 3 old crt monitors and found veristors that look like ceramic caps but usiwaly have no or a odd number. also usuwaly labeled vr on the board. i have also found a rectangle plastic part thought was one and checked the symbol and it shows 2 diodes arows pointing tords eachother. any idea what this is it only has 2 wires so it is not a shockety diode. i looked it up online and the site said that was the symbol for a gunn diode. but thay make microwares so i don't think that's right.