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In Reply to: whats that crackling? posted by EL Cheapo on July 31, 2002 at 21:16:53:
El C,Sounds like a bad contact or tube going South. If you are comfortable with the idea of looking under the hood of your baby and its 500+ volts DC (LETHAL range)... Then, you might try the old "chopstick" test. You need the amp connected to the speakers. No input. Low volume, amp on.
Take an pair of cheap chopsticks (the kind you need to split)---they MUST BE ALL WOOD. Use ONLY one stick and probe the sockets and all solder points from left to right in your amp. All resistors and caps. LEAVE YOUR LEFT HAND IN YOUR POCKET (if you are right-handed) while probing. You do not want to test the "path of least resistance" theory.
If you can exacerbate or induce the popping and crackling more by probing one section or component---you've probably isolated one of the culprits. Turn off amp. Drain the filter caps (use a draining resistor). Replace the culprit or resolder the bad solder point.
Now, try the test again---until you've rid yourself of the bad seed.
Diodes, caps, resistors can all dry out or crack. This can lead to crackling noises. So, I'd replace most resistors and caps in high heat areas. All ALL of the diodes in the PS circuit---just as preventative measure. Cause if they don't make noise now---they soon will.
All electrolytics caps (including cathode bias bypass caps) should be replaced. These are closest to the heat and often are way off OEM values, after 10-15 years of service. Go to a higher voltage rating, on the cap, if you want---it'll give you longer service. Eg: go from say 50 mfd/25 volts cap to a 50 mfd/50 volt cap. KEEP the mfd value the same.
Hope that this helps, a bit.
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Follow Ups
- Re: whats that crackling? - steven oda 22:56:26 07/31/02 (2)
- Re: whats that crackling? - EL Cheapo 15:24:30 08/01/02 (1)
- Re: whats that crackling? - Ron Oehlert 12:46:35 08/02/02 (0)