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AU-919 "Black Flag" Cap Replacement

Arnox

Arnox

New Member
Hello,
Newbie here, I have an AU-919 and am looking to replace the "Black Flag" caps as a minimum. Looking at using Ceramic C0G/NP0 caps, but they seem to only be avi rated up to 100v. The only reference to rated voltage I've seen so far is in the Lee’s Stereo write-up. There's only one mention of these cap rated voltage and that's on the Flat Amplifier (F-2841) board for C01 & C02 33pF caps, where Lee's replacements are 100v rated. My long winded questions is, can all the others be replaced with 100v rated caps too?

Thanks for your assistance,
Cheers Steve
 
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Some of the required values are available with much higher voltage ratings, obviously avoid the lower voltage ratings, (like 50V), and shoot for the highest that are available for the capacitance value needed. I have just been looking at Mouser and notice that 33pF are available with a rating as high as 630V, (with 5mm lead spacing), but 3pF are available with a maximum of 100V rating. The important thing is to be sure they are C0G/NP0 type.

33pF
https://www.mouser.co.uk/ProductDetail/Murata-Electronics/RCE5C2J330J2M1H03A?qs=sGAEpiMZZMt3KoXD5rJ2NwPv70zxIRBTZTwOzCvfgj8EIxJNbO2FKA==
3pF
https://www.mouser.co.uk/ProductDetail/Murata-Electronics/RCE5C2A3R0C0K1H03B?qs=sGAEpiMZZMt3KoXD5rJ2N7XzgPK/VHmNqM7nbs7TTxQ=

I make a habit of checking the voltage these capacitors are likely to 'see' in circuit and haven't found anything to worry about yet, although the higher voltage ratings are desirable in all cases. (I just checked the Murata website to make sure of the 630V voltage rating - it is correct).
 
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So if I got this right on the C0G/NP0 type I can use 100v rated if I can't get any higher. Also, I did some shopping for the Silver mica, found all but the 9's. And as I've read they are much more costly... Thx
 
Hello, almost done with the Black Flag cap replacements, but when I got to board F-2841, C31-34 that the schematic shows as 5pf are actually 3pf on my board. Has anyone seen this? And what value should I use? Thx for your input... Steve
 
You should always use the same value replacements as those that are in your amp Now - that's how it left the factory - right?
 
I agree, by default that's what I would do... Just wanted to see what others thought since its different from the documentation.
 
Arnox said:
I agree, by default that's what I would do... Just wanted to see what others thought since its different from the documentation.
Click to expand...
The original service manual won't reflect any "in production" changes that were made since it was printed. As John says (if it is original), always use what is in there unless someone has verified any changes/substitutions.
 
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