Pioneer SX-636 Receiver Restoration (including the addition of a pre-amp output).

This video is an attempt to describe the process I have gone through to restore and refurbish a lovely Pioneer SX-636 receiver, made in August 1974. I have really enjoyed working on this one.

In the video I describe my arrangements for converting the dial lighting to LED, using a custom 7V DC supply board. I show another custom circuit board which allows more convenient connections to the replacement main filter capacitors. I also describe the conversion of one of the tape outputs in to a pre-amp output (i.e. an output that would track with the adjustment of the volume and tone controls) using a third custom circuit board. I describe the circuit used, some tests done and also a brief outline of the process I have been using to get blank circuit boards manufactured.

(apologies - I am aware that the sound quality in this video is not brilliant; if I make any more of these I will invest in a proper microphone).

In this video:
00:00 Introduction
01:33 Lid off; replacement dial lighting and custom DC board
04:26 Dial lighting circuit diagram examination
08:14 Continuation of look at top side of receiver
11:10 Bottom side of receiver - look at custom filter capacitor board
12:42 Mains input area
14:46 Continuation of look at bottom side of receiver
16:40 Introducing idea for providing a pre-amp output
18:55 Pre-amp output buffer board design, circuit diagram
20:55 Bench tests of the pre-amp buffer board
23:56 Pre-amp board installed, further testing
26:29 Quick test of main amplifier output power
27:39 How I get my circuit boards made; quick look at Easy EDA
30:55 All finished; wrap-up.

This is totally a hobby; I am not intending to sell this or any other units I have restored - nor can I take on outside work. I'm just enjoying the process of slowly repairing, restoring and enhancing this beautifully made 1970s gear.

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
In particular for the SX 636, this post from MarkTheFixer is an excellent starting point for replacing transistors with modern equivalent parts. https://audiokarma.org/forums/index.p...

One of the absolutely best YouTube channels for hi-fi restoration is xraytonyb,    / 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.