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Tubes Asylum Questions about tubes and gear that glows. FAQ |
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Tubes Asylum Questions about tubes and gear that glows. FAQ |
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In Reply to: Re: Hiss in Point-to-Point Wired Tube Preamp posted by kevb on March 13, 2002 at 20:25:53:
Kevin,That sure sounds like a cap going South. If you are used to fixing the innerds of these things----you can try the "chopsticks" test.
Amp on, speakers connected, zero volume, no input.
Now, using an ALL WOODEN chopstick---gently tap the caps on the circuit. Go from input (power transformer) to output side. Tap the RCA plugs, also. Pay attention to those little round ceramic disc caps---they like to get noisy.
If any component or area seems to make more noise when tapped---you've probably isolated the stage.
Now, look for poor soldering, loose connections, and bad components.
If you find a bad cap (for instance)---DRAIN THE FILTER CAPS. I do this by:
1.) Turn off pre-amp.
2.) Unplug unit from wall outlet.
3.) Place a 100 ohm 5 watt resistor with 4 inch leads and alligator clips on both leads from---the positive side of the filter cap through your 100 ohm drain resistor, to ground (the chassis).
This will drain off the hundred of volts, left in your system, even after you've turn it off. Leave the drain resistor on, while working with the amp.
4.) Replace the bad component.
5.) Remove drain resistor.
6.) Chant mantra: "No noise... No noise" over and over ten times.
7.) Try unit.
Hope it works. Also watch for poor socket contacts, especially if you've been rolling 'em little doggies around. A bent tube prong can goof-up the socket. Slightly touch each tube with the unit on.
If any change in noise---you may need to re-tension that socket.
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Follow Ups
- Re: Hiss in Point-to-Point Wired Tube Preamp - steven oda 03/13/0222:56:57 03/13/02 (0)
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