Thursday, December 14, 2023

Another amplifer rebuild with a TDA7394 Power Amplifier board

Once again I am rebuilding another amplifer this time with a TDA7394 Power Amplifier board.  I picked up theis fried amplifier at a Hmfest from a friend for like $10 for the poweer transformer.  I tested the output transistors and all but one were shorted.  So I decided to rebuild it with a dual TDA7394 amplifier board for $22 on eBay.  The power transformer is 60 VCT so the rectified power is + and - 42 volts DC.  That is a little high for the IC but within its specs.  It should deliver 100 watts per channel into 8 ohms without any problems.

Here is the old circuit board.  The preamp seemed OK so I decided to try to save it.

So I cut the old circuit board in half with a hand saw.

This is the new power amplifier board, it is a lot smaller than what it replaced.

This is the new heatsink to go with the IC based power amplifier.

Here is the finished amplifier.  All it is missing is the power on LED and a shielded audio cable from the preamp output to the RCA jacks on the back panel.  The preamp had a slight buzz in it, I don't know why.  Perhaps better shielded audio cables would help.

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