AU-X1

[slimecity]

Leestereo - there's a capacitor handbook? I mean I like electronics and stuff, but the next time I cant sleep, I will need to look this up.....

lol.

 

[Ronito6]

There is some anecdotal evidence that current silver mica capacitors may be better sealed and hence able to withstand humidity and heat effects better. However, DC voltage may still be a problem; note that both Hewlett-Packard and Trimble Dayton Service Technologies specify in their respective engineering design guides that silver micas not be subject to DC voltage. Also, although no specific numbers are given, The Capacitor Handbook does state the following (pg. 97): "Silver ion migration can occur in only a few hours when silvered-mica capacitors are simultaneously exposed to DC voltage stresses, humidity, and high temperatures." Of course, YMMV, but caveat emptor!

Holy-moly! Got an ISBN or a publication date for that documentation?

 

[Ronito6]

Found it easily on Amazon.

Kind of read in haste your (Leestereo) posts #95 and #100. (Thursday's are D-Day at work.)
Got home and saw author and title. The rest sorted itself.

Here is the book
https://www.amazon.com/Capacitor-Ha...dp/0962852538?ie=UTF8&*Version*=1&*entries*=0

• Paperback: 140 pages
• Publisher: C J Publishing; 2 edition (August 17, 2011)
• Language: English
• ISBN-10: 0962852538
• ISBN-13: 978-0962852534
• Product Dimensions: 6 x 0.3 x 9 inches

There is some anecdotal evidence that current silver mica capacitors may be better sealed and hence able to withstand humidity and heat effects better. However, DC voltage may still be a problem; note that both Hewlett-Packard and Trimble Dayton Service Technologies specify in their respective engineering design guides that silver micas not be subject to DC voltage. Also, although no specific numbers are given, The Capacitor Handbook does state the following (pg. 97): "Silver ion migration can occur in only a few hours when silvered-mica capacitors are simultaneously exposed to DC voltage stresses, humidity, and high temperatures." Of course, YMMV, but caveat emptor!

 

[Leestereo]

Preview of The Capacitor Handbook on Google Books: https://books.google.ca/books?id=FOatBAAAQBAJ&printsec=frontcover#v=onepage&q&f=false

 

[ghamilton]

If I were to change some of those silver mica caps in my 919,...which ones should I change? I replaced ALL black flags with silver mica.

 

[Hyperion]

This should be a separate thread, we are crapping all over Willy6's AU-X1 thread here.

 

[ghamilton]

Your right. Sorry.

 

[Ronito6]

The question of "best capacitor" is naturally a fundamental one for any restoration.

So fundamental it can steer a thread off course.

On the other hand, while Willy is waiting for his delivery from Mouser, the loose end of C0G/NP0 vs MICA has been examined and sorted out.

Good info for one and all!

 

[Willy6]

Not bad news. Harolda has the same, and he can advise you how you can make your X1 nice and stable.

Apparently the source of the X1's instability was discovered by a tech in Germany, Martin Kuehne. Harold discovered his work.

Anyway, Mr Kuehne found that the source of the X1's oscillation problem came from bad grounding (for lack of a better description) on the 2819 flat amp.

Harold had a PM or two with Mr. Kuehne and applied Mr. Kuehne's grounding modification to his X1's 2819 flat amp board.

It is illustrated in his thread on posting #155 here http://audiokarma.org/forums/index....-output-transistor-replacements.684619/page-8

But to save you some time...

Should I use the c0g/Np0 type of ceramic caps for those three above or does it matter?

 

[Ronito6]

Should I use the c0g/Np0 type of ceramic caps for those three above or does it matter?

Seems switching "Black Flag" caps with C0G/NP0 is the most current way forward.

Does it matter? To me it would. Why bother with anything but what is agreed to be the best correct choice?

Hyperion and Leestereo seem to concur on the issue of C0G/NP0 being the better choice over Silver Mica, and have used C0G/NP0 caps in their respective restorations.

I did not. I went with Silver Mica.
But I now plan to remove them from DD / DC circuitry in the phono stage and (lordinheavengivemestregnth) driver boards.

Leestereo and Hyperion...do you have a good word here for Willy6?

= 20 Minutes Later=

Woop! Sorry Willy6. You were referring to the Martin Kuehne ground modification for the flat amp board.

The pictures in the posting you quoted were uploaded by Harolda.

His pics are very good, and you can clearly see what he used to make his supplemental ground lead. Just use the ones you see in the pic.

Barring those, I see no reason why C0G/NP0 caps would not serve as well.

 

[Willy6]

Seems switching "Black Flag" caps with C0G/NP0 is the most current way forward.

Does it matter? To me it would. Why bother with anything but what is agreed to be the best correct choice?

Hyperion and Leestereo seem to concur on the issue of C0G/NP0 being the better choice over Silver Mica, and have used C0G/NP0 caps in their respective restorations.

I did not. I went with Silver Mica.
But I now plan to remove them from DD / DC circuitry in the phono stage and (lordinheavengivemestregnth) driver boards.

Leestereo and Hyperion...do you have a good word here for Willy6?

I'm talking abut the three used for the grounding to prevent oscillation.

 

[Ronito6]

I'm talking abut the three used for the grounding to prevent oscillation.

The ones used in Harold's (Martin Kuehne's) ground mod pics are not ceramic caps. I see no reason why ceramic would not work.

I would just use the same kind in the pics.

 

[Hyperion]

I would just use the same kind in the pics.

Yep, use film capacitors - just as Harold and I have done.

Don't run away with the idea that ceramic capacitors are so good you can use them for anything - not the case - there are specific and best uses for all the dielectric types.

 

[Willy6]

Yep, use film capacitors - just as Harold and I have done.

Don't run away with the idea that ceramic capacitors are so good you can use them for anything - not the case - there are specific and best uses for all the dielectric types.

Is there any specific type of film cap I need?I have that capicitor hand book on order as i'm still trying to learn the various types and what they are used for and thanks again for all your help.

 

[Hyperion]

I am pretty sure I used these :

http://www.mouser.co.uk/ProductDeta...GAEpiMZZMv1cc3ydrPrF0%2bjlB8SXIRuiUC7BPolpLE=

 

[ghamilton]

After all the talk about this newer type of ceramic instead of silver mica, I guess I would consider the COG/NPO ceramic if I had not already done the overhaul. I think it's kind of silly to go back in there just for this. The silver mica caps will stay in there. They will probably out last the black flags and electrolytics!

 

[Hyperion]

Good decision ghamilton, my own precious AU-919 has been done with Silver Mica, and I won't be changing mine.

 

[Willy6]

I measured the current gain on the 6 outputs on the right side and they're all different.
PNP
HFE=63
HFE=44
HFE=53
NPN
HFE=39
HFE=47
HFE=68
Should I keep these or replace them with new ones?

 

[Willy6]

I measured the current gain on the 6 outputs on the right side and they're all different.
PNP
HFE=63
HFE=44
HFE=53
NPN
HFE=39
HFE=47
HFE=68
Should I keep these or replace them with new ones?

I still have 18 of them between the two amps that I haven't checked yet.

 

[Hyperion]

I measured the current gain on the 6 outputs on the right side and they're all different.
PNP
HFE=63
HFE=44
HFE=53
NPN
HFE=39
HFE=47
HFE=68
Should I keep these or replace them with new ones?

You will be very lucky to find 'new ones' anywhere, as the OP transistors haven't been made for decades. When I removed mine I checked they were OK but kept the transistors from each channel separate, and noted their positions.

If you find that you can't make a complete set, or you can make one set but not two, then you should (on one amp) change them all for T03P substitutes, like the guy with the AU-X11 did so well in his thread.