Beyond the list of standard restoration steps detailed on the main page, here are some added notes for this unit :

I bought this at a local swap meet and was told “it only needs a good cleaning”.  Exterior condition was very good with some dings in the wood cabinet.

Long discussion of features follows

The QX747 is an early/mid 70s quad receiver and has many added features (most usable in 2 channel mode) 

4 channel amplifier mode – 4 identical amplifier channels enabled (20 watts per channel, 8 ohms) 

2 channel amplifier mode – 2 of the 4 amplifier channels are active and operate at higher supply levels (40 watts per channel, 8 ohms) 

Modes for CD-4, RM and SQ (4 channel input format decoders if connected to 4 channel turntables or tape decks)  

Visual display showing dynamic output levels on all 4 channels with 4 balance controls for left, right, front and rear

Independent bass/treble controls for front and rear speakers

Resulting unusual 2 channels capabilities 

In CD-4 mode stereo content is sent unaltered to both front and rear speakers.  This allows optimizing output levels and bass/treble for 1 pair of speaker vs another pair of speakers.  If using 4 identical speakers, then compensating for relative positioning and/or sonic qualities (drapes, etc).  Even more interesting is being able to balance level and tone settings for 2 sets of different speaker types.

In RM and SQ modes, stereo content is processed (via phase manipulations) which Pioneer says can result in “a pleasant effect” (RM mode) and “a pleasant depth effect resembling a concert hall” (SQ mode).

In all 4 channel modes, each of the 4 amplifier channels can drive speakers from 16 ohms to 4 ohms.  This uniquely allows connecting/driving four 4 ohm speakers (not allowed for normal stereo amplifiers).

The restoration was uneventful as this unit was highly functional from the start.  It was a marathon as this receiver is jam-packed with circuitry making them very challenging to restore.  To illustrate, I replaced roughly 2 times the number of caps and 3 times the number of noisy transistors as the SX939 I recently finished.  Because of this, it is very rare to find one of these fully recapped (the labor cost alone would make this very prohibitively expensive at a service shop).  

The matrix output level display has 3 range settings and is interesting to watch (sending out green diagonal lines to show dynamic power for all 4 channels). 

The tuner works very well and the overall sound is quite nice.

It cleaned up nicely with the faceplate, dial and knobs all being very clean.  The wood cabinet looks fine from the front/top but has dings on the sides (see photos). 

IMPORTANT NOTE

I am unable to test functionality in the 4 channel formats using anything other than stereo inputs.  The 4 channel mode circuitry does handle stereo as expected, but I could not test/calibrate CD-4, RM or SQ modes with 4 channel sources.  A purchaser has the normal 30 days to test these modes in their 4 channel systems and return this if not sounding right.

The stereo behaviors are well tested (as usual).