Pioneer SA-9100 - repair, calibration and sourcing of obsolete switches and pots.

Several of these Pioneer SA-9100s have passed over the work bench over the years, and as owner reviews will profess, such a beautiful, warm sound, which I would compare equally to the warm sound of the Accuphase E-303. I worked on both of these first within a few months of each other many years ago, when I had the luxury of being able to spend more than a short period of time function testing a repaired amplifier - setting up for a few records listening session, to really appreciate the sound and tonal quality design engineers had created with each model. When you spend extra, major brands, and most boutique brands of the last few decades, certainly deliver with amplifier sound quality and listening experience.

This beautiful example was the most recent, and whilst previous jobs ranged from service/calibration to involved repair with numerous faults, this one led off in a different direction. Sight inspection revealed the cleanest 40+ year old amplifier I had seen in a long time, but was deceiving, as discovered after a function test - deep crackle as the pots and switches were actioned. Freely, with no resistance to movement, this has been observed before and warranted further testing with the oscilloscope.

Crackly/noisy pots are a common symptom, that is widely misconceived from users, in that they just need a quick "dexoit" and away they go....thats the most common thing people here on the internet I suppose :-) Crackle from pots can be dust/contamination, but can equally indicate unhealthy voltage within the audio path and rarely, as in this case, heavy oxidization/environmental damage to the brushes and resistive tracks.

This is where the client benefited in taking his amplifier to a technical workshop. Connecting an oscilloscope and performing various tests along both the audio and power circuits pinpointed and clearly indicated the areas of mechanical damage and unhealthy circuitry. Identifying this difference was vital to a correct diagnosis, and I've no problem saying that I measured thrice, before taking the "cut". These SA-9100s can be involved, as the vertical mount PCBs do make pose a barrier to easy access to every single component within a circuit. Ive had to "jig up" PCBs within these and SA-7100s to diagnose, in some cases.

...diagnosis was only the start, as replacement volume, balance, loudness and low filter switches and pots were required. Fortunately, AST Repair Perth does have reliable sources for more top end vintage amplifier assemblies - Pioneer, Luxman, Accuphase, Denon, Technics, among others, plus turntable mechanics and inner assemblies. All are tested and harvested from units with minor faults or large areas of chassis cosmetic damage. One of the only "silver linings" to come from the mid 2020 period, this main contact was discovered when searching high and low for a (tested) replacement volume pot on a Sansui AU-7900, of which the owner was happy to pay for sourcing time and expressed no urgency, understanding these processes cannot be rushed.

With the costing acquired for further work and parts costs, the job could advance. Whilst outside the clients budget, being close to $1000, with these assemblies, the sound quality and user experience of this top of the range model, was the deciding factor to go ahead. Being referred is also a big factor, in the decision to go ahead with a large job such as this. Having a reliable parts source, was the only way however, and AST Repair Perth is the only workshop to be able to provide this select service in WA.

Once complete, calibrated and tested, the result was a close to a new SA-9100 as possible. Paired with a Technics SL-1300, purchased from the same owner, the new one was ready for a high end listening experience reminiscent of his youth.