ARCHIVED FORUM -- March 2012 to February 2022READ ONLY FORUM
This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
Hi all,
I have just purchased a Beocenter 3500 which is working but...
The (power?) transistors in the heatsinks on the rear of the amp are getting hot almost immediately. Also one channel is hotter than the other. If this was a class A amp I'd not be concerned but of course its not.
I have not connected any loudspeakers yet.
I have checked DC offset and one channel is about 70mV and the other about 0.4V!! Clearly something is amiss
Looking inside one of the 3000uf output caps does have a bulge in its base so maybe its these caps that are the issue?
Any thoughts?
Also what replacement caps should I use for the PS and the outputs (5000uf and 3000uf 70v respectively)
Many thanks
Mark
DC offset? I don't get it!
Jacques
"DC offset (also known as DC bias) is a concept employed when dealing with electrical components, most notably audio equipment.
These components send either power or audio signals using alternating current (AC), by which the signal reverses direction regularly. If the signal does not spend an equal amount of time traveling in both directions, however, the resulting imbalance is referred to as DC offset.
A high level of DC offset can damage electrical components and degrade signal quality. The guide below will teach you how to measure DC offset using perhaps the classic application - a stereo receiver or amplifier.
The ideal amount of DC offset is 0, which results from a perfectly balanced AC sine wave. In reality, an offset between 0 and 20 mV is very good. An offset between 20 and 50 mV is slightly higher than the ideal range, but the distortion caused will barely be audible. A range from 50 to 100 mV will begin to cause noticeable degradation of the audio quality, while an offset over 100 mV may cause permanent damage to your speakers."
I suggest you replace the idle current trimmers and adjust to factory specs.Then check the DC offset again and diagnose any eventual remaining faults.
Martin