Re: Stereo Power Amp Problem
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A few thoughts I have about this problem:
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What is the volume setting? Does the noise level change when changing the volume level? Is this in a noisy RF environment? Do you have flourescent lights on? I do telecom work, and whenever I run across a noisy phone with the speakerphone buzzing, I pull out my fox/hound tracer. With a quick push of a button, it will amplify any noisy environment in the AF range for the most part. I will wave it around the room monitoring the audio. Whenever I shutoff the flourescent lights, it will immediately quiet down. Another great way to use it is to trace the problem in the amplifier. It will especially work well because it is AF, not RF. It is very sensitive too. I have placed a signal from the fox signal generator on the pre-in and quickly traced it thru the amplifier by just placing the tip near the amplifying components. Just don't place it on the 120VAC directly, I did that once and blew the first stage amplifier out. Just a small transistor and easy fix. I also use it to see if slow processors are active. They make noise too. It is a very smart investment for troubleshooting. You can use it to judge the amp stages by the loudness in/out. I would sub out the power supply too if it can be easily done. But I would say most of all ensure of the bonding. ground out the chassis to earth ground. I have been reading up on my NEETS Basic Electronics manual and have just been studying power supplies. A very good book and free too. It might be dated, but so is your P/S. Just google NEETS, and you can get the whole series too. Place the amplifier in a completely different environment. Did you plug in some other device in the house that might be backfeeding on the wall outlet? And of course, isolate everything. In telecom, whenever I troubleshoot a noisy circuit/wire pair, It is almost always an unbalanced cable pair. Whether it is due to a wet cable changing the capacitance between conductors, or one of the conductors has a lower resistance to ground thru a damaged cable. Make sure your pre-amp signal cable is OK. Also ground/jumper out the preamp in center pin of the RCA connector. If it is picking up noisy environment, this should quiet it down. Make sure you did not break the solder trace at the preamp in RCA. If it did on the ground, it will howl! Just looking at the specs of this amp, it is very impressive! Nick --- In TekScopes@..., "Bill McDonald" <BillM256@...> wrote:
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