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filter cap health...

4/25/2003 1:45 PM
josh camp
filter cap health...
i have a feeling i may have burnt out one or more of my filter caps in my 5e3 homebrew... how can i determine if i have damaged them in any way other than the obvious...?
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4/27/2003 8:03 PM
MJ Harnish
In generaly you ought to have a lot of 120 hZ noise (i.e., a low frequency hum) or have motor-boating problems. It doesn't sound like your experiencing obvious problems so I doubt your caps are bad. Howe exactly did you "burn them out?"  
4/28/2003 12:46 PM
josh camp

well, i thought maybe i might have applied too much solder iron heat from repetitive soldering - resoldering, etc... the symptoms are mostly hiss now - as i have reduced a lot of hum by reorganizing the lead dress and other wires...  
the hiss gets louder with volume and higher tone.  
i am still not experiencing a lot of 'overdrive' the amp remains rather clean at higher volumes.
4/28/2003 3:56 PM
MJ Harnish
As far as ruining your caps by repetitive soldering, it's unlikely unless you're using a big soldering iron or really poor technique. The type of cap also probably makes a difference; Sprague Atoms are much beefier than say Illinois caps. Anything's possible though. :)  
Hiss is not likely to have anything to do with filter caps; most likely it has to do with lead dress, poor grounding, environmental factors, etc. The fact that it gets louder as you turn up the volume and tone suggests it's getting into the circuit prior to that point in the circuit.  
Are you using a shielded cable running from the input?  
What type of resistors are you using?  
Are you using the Fender 5E3 layout or something else?  
Why type of grounding scheme are you using?
4/28/2003 5:45 PM
josh camp

i am using mostly metal film resistors, except for a few carbon comp - i know those a re probably suspect.. as for the shielded cable on input - i did use shielded cable here and there - except for the grounds. this is the mission amps tweedy deluxe 5e3.  
i am using a star grounding scheme throughout - separating power and preamp sections  
thaks for your help.  
4/29/2003 7:31 AM
MJ Harnish
I would contact Bruce in that case b/c he's really good about customer support.  
My first suggestion would be to get rid of the carbon comp resistors and see if that improves things. CCs can be a PITA when it comes to noise; sometimes you have no problems and sometimes you've got all kinds of sqeaks, hisses, and squeals. I had an old Deluxe Reverb that used to sound like squirrels were inside it being tortured from time to time while it was warming up. :(
5/3/2003 4:33 AM
Mark Lavelle

"i am using mostly metal film resistors, except for a few carbon comp - i know those are probably suspect."
One place you definitely don't want carbon comp resistors is on the plates of your preamp tubes.

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