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Tube mono-block amp with SIX 6L6 outut tubes
"Big Bad Bob" wrote in message
... On 12/28/18 09:16, bitrex wrote: All amps of that scale should have active protection circuitry/monitoring of currents, biases, and temperatures via microprocessor to avoid potentially catastrophic faults. Even briefly overvolt or overcurrent on a typical transistor, and you'll be replacing it VERY soon. I made the mistake of designing a circuit that operated close to the maximum Vceo (these 60V transistors should be able to handle 45-50V right?), and the transistors never lasted long under load (replaced 3 times, and 3 blown fuses that were supposed to protect them). Replaced with transistors that had twice the Vceo and no problem. Well... overcurrent on a mosfet output device is usually pretty safe for quite a while. Second breakdown is the problem with bipolar. Their rating at high voltage is much lower than their power ratings would imply. I designed mosfet amp in the early 80s. I tested it by putting in a full level signal with an output s/c. The only protection was a zener across the gates to limit the current to the device ratings. I left it cycling with its 90 Deg heatsink thermal cutout for 3 days. No problems. -- Kevin Aylward http://www.anasoft.co.uk - SuperSpice http://www.kevinaylward.co.uk/ee/index.html |
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