Capacitors, again

paulrichards7 · Post by **paulrichards7** » Tue Jan 13, 2009 6:05 pm

As Im not having any luck finding the source of the noise on my channels of Studiomaster 16-4-8
Im just gonna go ahaed and do a recap and see if that helps
Here is a quote from Jim Williams

"Add some local .1 uf mono ceramic psu bypasses off these chips, pins 4 and 8 to ground. Check with a scope for stability.

Remove the green/red "chicklets" mylar EQ caps. Use Wima FKP-2 or MKP-2.

Replace electrolytic caps with Panasonic FM or Nichicon HE. This includes side chain and psu bypass caps. Bypass signal EL caps with Wima .01 uf MKP-2, these are fitted on the trace side of the pcb"

Ive read in other places about grounding the pins of ICs
Will definetely be changing those chicklet EQ caps
Now as my PSU is putting out 15v, I was thinking of replacing caps with 25v caps, unless it requires higher values
But what voltage should the Wimas be?
And any other tips or suggestions
Thanks
Paul

bibleboy3 · Post by **bibleboy3** » Tue Jan 13, 2009 9:33 pm

ceramic caps can be a noise source themselves I would avoid ceramics caps .

Jim Williams · Post by **Jim Williams** » Wed Jan 14, 2009 8:28 am

Ceramics are fine and prefered for power supply decoupling. Films are best for audio. Noise (hiss) is usually semiconductor sourced. Try new transistors and opamps.

paulrichards7 · Post by **paulrichards7** » Wed Jan 14, 2009 11:08 am

Thanks for that Jim
The transistors that are in there are 2sa970 which are now out of production
Any ideas of a replacement?
The TL072 are the opams
I was thinking of changing them for 5532s, but only running about 12 channels instead of the 22
Do you think it would work?
I think in an earlier post you recommended .01uf/250v WIMAs and electrolytics of at least 220uf for channels
Is this correct?
Thanks once again for all of your help
Paul

Jim Williams · Post by **Jim Williams** » Thu Jan 15, 2009 8:20 am

2SB737 or 2SA1083's.

paulrichards7 · Post by **paulrichards7** » Thu Jan 15, 2009 9:38 am

Thanks for that Jim
was i right about your earlier postings?
see post above
Thanks
Paul

argonautlabs · Post by **argonautlabs** » Thu Jan 15, 2009 5:04 pm

Personally, I would try to localize the source of the noise before just changing out components. "Upgrading" (if you can even call it that) probably will not get to the root of the problem. If most of the gain stages and filters are opamp designs it should be pretty easy to go through the circuit stage by stage and figure out where the noise is coming from. I would tend to agree that it is more likely to be semiconductor problem than passive components. Mylar and ceramics don't fail all that often. From experience though, most of my troubleshooting usually ends up in some sort of connection or grounding problem. Don't get caught up in the whole "circuits with these components are horrible" smooze. My advice is get a schematic and do some text book reading if you arent up to snuff on circuits as the internet is full of a lot of bad advice, mine included.

paulrichards7 · Post by **paulrichards7** » Wed Jan 28, 2009 7:34 pm

I have replaced all ICs, transistors, diodes and resoldered all connections
Still noise?
Paul

Message Board

Capacitors, again

Capacitors, again

Who is online