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

SA900

I bought this from Goodwill (“powers on”) with very good cosmetics.  

Initial inspection showed that the power switch was extremely stiff.  After removing the faceplate and covers, I repeatedly lubricated the mechanism until it operated normally.  The switch contacts were fine, the shaft was just gunked up. After cleaning all the switches and pots, initial functional testing went fine.

Normal DC power supply checks showed several rails significantly over spec (example 40V supply was sitting at 53V).  I tracked this back to a bad 13V zener diode.  Replacing that returned all power outputs to correct ranges.  This was a “silent” failure that was over stressing components in the the preamps, etc and would not have been caught by folks just powering things up and saying “works as it should”.  

Given how nice an amplifier this is, I decided to upgrade the speaker terminals from the Pioneer “plugs” to modern 5-ways (see photos of the back).

Recap went smoothly and final functional testing was completed/passed.  Nice sounding cap-coupled amplifier.

TX900

First one I purchased from Goodwill had the AC input level incorrectly set to 110V (rather than 117V).  This causes all internal voltage to be ~5% too high and corrected this. The RF section then proved to be faulty and unusable.

Rather than attempting to purchase/swap in a replacement part, I decided to buy another TX900 on ebay.  This one had nearly perfect cosmetics and the seller proved to be quite honest as he refunded me some of the shipping cost after finding a cheaper option.

Initial inspection confirmed excellent cosmetics.  After partial disassembly and switch/pot cleaning, it fired up fine with all functions working well – really an exceptional example.  

Recap and new lamps went smoothly,  While some early Pioneer tuners can be rather finicky to align, this one was rather easy to dial in (even without alignment instructions in the service manual).  It is sensitive and has a very pleasant FM stereo sound.