Wednesday, February 16, 2011

Dunlap Clarke Amplifier Rebuild

I am once again rebuilding this Dunlap Clark amplifier. I rebuilt it around 1990 to a four channel 200 watt per channel amplifier after teh first system fried. Then a few year I got it back with two channels fried and I just fried the last channel in my latest youtube video 'comparing coils'.
The first repair was to modify the power transformer to reduce it to 60 volts center taped from 100 volts center taped.  This involved pulling out some windings and adding some jumpers around some of the windings.
This is a picture of the heat sinks witht eh TO-3 output transistors.  I will likely use TDA7294 IC's to rebuild it so the old transistors have to go!
Out of all the transistors there were only 11 that were not totally fried.  One even had the emitter lead burnt off the transistor!
The TDA7294 circuit board finally arrived. It comes in several configurations. Four 75 watt amplifiers, two 150 watt amplifiers, one 300 watt amplifier and a combination of one 150 watt and two 75 watt amplifiers. they sell for around $30 on Ebay.  Now the problem is mounting it in the heat-sink, it will require putting in smaller capacitors and drilling holes to align with the TDA7294's.


YouTube video of amplifier accidentally being fried.
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