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Multilayer Ceramic instead of Mica Capacitors
#1

Hello Everyone,
The topic of the day is using Multilayer Ceramic Capacitors Instead Mica Capacitors .
As you guys have known Mica Capacitors  prices are getting more expensive and some values are getting harder to get .
More and More I am seeing that dreaded monster Silver migration Disease and the current value that I need to stock up on and use in a General Electric 1950s clock radio 110 PF.

I found these  Multilayer Ceramic capacitors made by Kemet


It does say  Class I "stable" material. Components of this classification are temperature compensating and are suited for resonant circuit applications or those where Q and stability of capacitance characteristics are required.

https://www.mouser.com/datasheet/2/447/K...316440.pdf

Sincerely Richard
#2

Rich

an NP0 (C0G) cap is a better cap when it comes to stability, so if you could find a cap that is an NP0 with the proper capacitance vs WV, use it. Micas are very good and stable, and due to more capacitance per volume unit and higher WV are preferred in some circuits.
The rest, well, could be use in some places and should not be used anywhere where the stability of Mica is important.

People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
#3

I guess I'm going to have to mold my own from that hunk of South Dakota Mica I have up at the cabin. Let's see, a slice of mica, couple "plates" and some JB Weld should be just fine (maybe some colored markers to show the value). Come on kids, it's craft time!
#4

Hello Rob,
Yes , I could do this as a classroom project go to mouser and look at some the prices for the larger Mica capacitors I just went to mouser and looked at a 7500pf at 500 volts around $22.00 that crazy right buy 10 of those .

morzh,
Those are NPO rated Capacitors https://www.mouser.com/ProductDetail/80-C315C111JCG

Sincerely Richard



[url=https://www.mouser.com/ProductDetail/80-C315C111JCG][/url]P0)


Attached Files Image(s)
   
#5

Rich

For the purpose, I do not think anything beats NP0. They simply did not exist at the time, and the mica were the best (and they are great, considering they are as good today as they were the day they were made). But C0G has Zero ppm temp drift.

People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
#6

SMD is silver migration disease, not silver mica disease. If you think mica capacitors have gotten expensive, look at the prices of some silver mica capacitors. I have plenty of experience with silver mica capacitors used in professional electronics, especially in broadcast transmitters.

Dale H. Cook, GR/HP/Tek Collector, Roanoke/Lynchburg, VA
https://plymouthcolony.net/starcity/radios/
#7

Not too bad.....yes, expensive. More expensive than the rest.


Micas
https://www.mouser.com/c/passive-compone...ng=500%20V

(look only at the stock ones) $2.50 to $3.60 @ 10pcs



NP0
https://www.mouser.com/c/passive-compone...=500%20VDC

These are $1.30 @10pcs

People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
#8

Hello Dale,
Yes I meant migration ! it was a long week .
for sure when buying those silver mica capacitors you need a home loan to buy I do have some in my stock .

morzh I will order those Kemet capacitors .


Sincerely Richard
#9

The IF cans used in Japanese radios used either molded mica or those ceramic capacitors that look like a hollow dog bone resistor. In West German sets they used the dog bone ceramic jobs, as well as polystyrene, in tuned circuits, I guess that mica was harder to come by for them?
Regards
Arran
#10

Hello Arran
Yes, I have seen those hollow dogbone style capacitors and I have some NOS ones in my inventor !

Sincerely Richard
#11

I use caution when replacing defective mica caps in frequency determining circuits. Often, they have a tempco even if not marked so the tuned circuit stays stable as the coil drifts with temperature. The earlier the radio the more likely the component is "house marked"

Same applies to the "dogbone" ceramics these are often tempco any more than three dots are suspect but where it is in the circuit is often a clue.

One of my first re-capping experience (1965) was with a Hammarlund SP-110-x horrible drift and unable to calibrate the center of the bands both RF and oscillator circuits. The OEM open mica caps were of a special brass/steel clinched (liken to bi-metal) construction that remained stable. However, time and moisture ruined them. Finding suitable values and temco was cut and try, the schematic available did not give values, though I no longer remember the value they were N330.

IMHO I do not think drift in a 455khz (sic) IF is a problem, I have not noticed it, but drift in a receiver that uses a higher IF such as a dual conversion drift in the IF is suspect.

The "discovery"  of what appears to be a sure thing replacement for a mica condenser should not be an excuse to shotgun.

Chas

Pliny the younger
“nihil novum nihil varium nihil quod non semel spectasse sufficiat”
#12

Just an oddity.  The attached photos are of an 80+ year-old 250pf Micamold cap. Note that the body is cracked and open.  It still measures 250pf!

   
   
   

Joe

Matthew 16:26 "For what does it profit a man if he gain the whole world, yet lose his own soul?"
#13

I make it a rule not to touch the mica caps unless explicitly damaged.

People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.




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