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| General Electronics Chat This forum is for general chat about electronics, eg: Dont know what a part does? Dont know how to read a circuit? Want to get an opinion? |
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| Experienced Member | Hey guys, I'm about to replace a pair of snubber capacitors for the horizontal output transistor of a computer monitor. The original are 0.004 uf 1600 volt mylars, you know, those orange colored ones whose outer skin is made of what looks like a tough plastic. But all I can get of the same value are ceramic disks with a better voltage rating of 2 kv. I don't see any reason why I can't use the latter. Am I right? Last edited by berniedd; 22nd July 2006 at 02:54 PM. |
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| Super Moderator | Try them and see! - I certainly would!. |
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| Experienced Member | A metalized plastic capacitor can take an overvoltage spike and it just vapourises a tiny portion of the metalization and the circuit keeps working. A ceramic capacitor would just short and the circuit blows up.
__________________ Uncle $crooge |
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| Experienced Member | Aha! Good thing I'm replacing them with units of higher voltage ratings. |
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| Experienced Member | But the film capacitors "heal" themselves and the ceramic ones short. What voltage rating would be safe for the circuit to use ceramic caps? Why didn't the manufacturer use cheaper ceramic caps?
__________________ Uncle $crooge |
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| Experienced Member | Different dielectrics will exhibit different impedances - I would be careful.
__________________ "Everything that is done in the world is done by hope." -Martin Luther "There are two ways to live your life. One is as though nothing is a miracle. The other is as though everything is a miracle."-Albert Einstein |
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| Experienced Member | Only metalized Mylar caps (and air or vacuum caps) will heal themselves. Regular Mylar film will not self-heal.
__________________ Dean Huster, Electronics Curmudgeon Contributing Editor emeritus, "Q & A", of the former "Poptronics" magazine (formerly "Popular Electronics" and "Electronics Now" magazines). R.I.P. |
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| Experienced Member | Do they still make capacitors with foil separate from the insulator?
__________________ Uncle $crooge |
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| Experienced Member | I just talked with a technician who said he's tried replacing mylars with ceramic disks of identical ratings in the flyback circuits. The results were unsatisfactory - the ceramic disks just shorted out. I guess that answers my question. |
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| Super Moderator | I've been repairing TV's professionally for 35 years, you see BOTH types used in original production - the 2KV ceramics are commonly used directly across collector/emitter of the LOPT transistor for tuning the LOPTX. |
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| Experienced Member | Aha again !! Looks like it's worth a try. |
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