Pioneer SA-9100 restored - Thanks to all who contribute to this forum
I discovered Audiokarma.org via google search when I was asked to repair a Pioneer SA-9100 that had been given to my brother. I have quite a bit of electronics experience but had never taken on attempting to repair a vintage amp as nice as this one. I learned from this forum that the 'protection fault' mode that this amp was stuck in was very common and I was amazed to discover the detailed information regarding the typical issues that cause this and how to repair it. I read and read and read the threads on the forum pulling together the various experiences of others and the recommendations of the gurus of the forum.
This unit had a cooked voltage regulator board (AWR-032). It was obvious when I tore the unit down with it’s fractured resistors, oozing caps and the browning of the PCB. The main audio amplifiers hardly looked used and had no signs of heat fatigue. I suspect the unit spent a lot of time on but running at very low volume and was rarely ever pushed to do any real audio work.
I purchased everything from Mouser for about 40 bucks and I spent about 8 hours on the actual repair work. I re-capped the two power supply boards, two main amplifier boards, and the protection board. I replaced the failed resistors, diodes, and transistors on the voltage regulator board (AWR-032) and the main driver transistor (Q1) for the protection relay on the protection board (AWM-025). I also added the recommended fly-back diode to the relay coil.
My story has a very happy ending. The unit sprang to life with rock solid voltages from the power supply and it came out of protection after the normal few second delay after power on. After performing the amp alignment and working DeoxIT into all the switches and pots it operates and sounds awesome. It is back with my brother and has been working perfectly for several weeks.
Without all the work done by the members of Audiokarma to identify suitable replacement components it would have been much harder for me to do this project. Thanks to all of you and especially markthefixer for taking the time to post what he has learned about repairing these units and what are good substitutions for the obsolete components that are no longer available from mainstream suppliers.
THANK YOU ALL!