Are mylar and disk ceramic capacitors interchangeable? - Electronic Circuits Projects Diagrams Free

berniedd · 22nd July 2006, 02:51 PM

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?

**Nigel Goodwin** · 22nd July 2006, 03:11 PM

Try them and see! - I certainly would!.

audioguru · 22nd July 2006, 04:51 PM

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.

berniedd · 23rd July 2006, 02:50 PM

Aha! Good thing I'm replacing them with units of higher voltage ratings.

audioguru · 23rd July 2006, 03:30 PM

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 · 24th July 2006, 11:21 AM

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

Dean Huster · 24th July 2006, 12:56 PM

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

audioguru · 24th July 2006, 01:02 PM

Do they still make capacitors with foil separate from the insulator?

berniedd · 25th July 2006, 12:52 PM

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** · 25th July 2006, 03:34 PM

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.

berniedd · 26th July 2006, 04:57 PM

Aha again !! Looks like it's worth a try.

22nd July 2006, 02:51 PM	(permalink)
berniedd Experienced Member	Are mylar and disk ceramic capacitors interchangeable? 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.

22nd July 2006, 03:11 PM	(permalink)
Nigel Goodwin Super Moderator	Try them and see! - I certainly would!. __________________ PIC programmer software, and PIC Tutorials at: http://www.winpicprog.co.uk

22nd July 2006, 04:51 PM	(permalink)
audioguru 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

23rd July 2006, 02:50 PM	(permalink)
berniedd Experienced Member	Are mylar and disk ceramic capacitors interchangeable? Aha! Good thing I'm replacing them with units of higher voltage ratings.

23rd July 2006, 03:30 PM	(permalink)
audioguru 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

24th July 2006, 11:21 AM	(permalink)
Analog 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

24th July 2006, 12:56 PM	(permalink)
Dean Huster 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.

24th July 2006, 01:02 PM	(permalink)
audioguru Experienced Member	Do they still make capacitors with foil separate from the insulator? __________________ Uncle $crooge

25th July 2006, 12:52 PM	(permalink)
berniedd 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.

25th July 2006, 03:34 PM	(permalink)
Nigel Goodwin 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. __________________ PIC programmer software, and PIC Tutorials at: http://www.winpicprog.co.uk

26th July 2006, 04:57 PM	(permalink)
berniedd Experienced Member	Aha again !! Looks like it's worth a try.

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