Pioneer SX-750 Receiver Restoration (with power relay installation and oscillation problem fix)

This video attempts to describe some of the key stages in the process of restoring a Pioneer SX-750 receiver. In the video I discuss converting the lighting to LED and replacing the main filter capacitors, with the use of an adaptor board to make the terminations easier. I demonstrate and fix an oscillation problem in the power amplifier and show how that problem can be detected with an AM radio. I show how I added a relay for the mains power switching, to reduce the load on the damaged power switch. I show the installation of a pre-amp board, to provide a buffered output for my sub-woofer. I show the refurbishment of the power supply and protect board, and some changes to improve thermal management. I demonstrate a problem with the AM receiver chip on this unit, and how I replaced the four op-amp chips and the troublesome 2SA798 transistors. The circuit for the pre-amp was adapted from a circuit found on this excellent web site run by Max Robinson: https://www.angelfire.com/electronic/... The Audiokarma web site is great for tips about all sorts of hi-fi restoration, common issues and suitable modern replacement transistors: https://audiokarma.org/forums/index.php One of the absolutely best YouTube channels for hi-fi restoration is    / @xraytonyb  . Tony is incredibly knowledgeable, as well as being an excellent and engaging teacher. There are practical restorations as well as theory videos (or sometimes a mix of both). There is a lot of content on this channel, highly recommended! I also have to link to Mr. Carlson's Lab YouTube channel,    / @mrcarlsonslab   . Mr. Carlson (Paul) has amazing knowledge of old and new electronics, as well as the most incredible array of test equipment. He does things the right way! Quite astonishing, he also has a wealth of educational videos and projects to make on his Patreon channel. Again, highly recommended. An absolutely brilliant channel is Mend It Mark,    / @menditmark   . Mark is very skilled indeed at all aspects of electronics repair and fabrication of unobtainable parts. He has a lovely cheerful personality and is very engaging to watch. Chapters: 00:00 Introduction 04:54 Lighting conversion to LED 09:13 Filter capacitor replacement 12:13 Power amplifier oscillation problem - exploration and fix 20:03 Adding a mains relay to switch the receiver 28:24 Discussion of the custom pre-amp module 35:20 Refurbishment of the Power Supply and Protect board, and thermal management improvements 39:53 AM reception problem and diagnosis 44:29 Replacing the TA7136 op-amps with OPA604. 46:50 Replacing the 2SA798 dual transistors 49:07 Wrap-up.