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Are mylar and disk ceramic capacitors interchangeable?

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berniedd

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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?
 
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audioguru

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Most Helpful 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.
 

audioguru

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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?
 

Analog

New Member
Different dielectrics will exhibit different impedances - I would be careful.
 

Dean Huster

Well-Known Member
Only metalized Mylar caps (and air or vacuum caps) will heal themselves. Regular Mylar film will not self-heal.
 

audioguru

Well-Known Member
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Do they still make capacitors with foil separate from the insulator?
 

berniedd

New 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.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
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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