All of these have something in common – the easy to reach components replaced, whilst none of the hand wired, and essential ones, have been replaced. No elementary maintenance procedures performed, as should be the case with 40 year old amplifiers that have never been worked on previously.
The second TEAC AS-100 to pass over the workbench over the last few months, with both having nearly identical “work” performed. One owner supplied a hand written note detailing issues resolved, but none of the work performed corresponded to the main circuit worked on..
The other was bought second hand, advertised as “serviced and re-capped”. Brought to me with uneven output on the left and right channels. The seller said the work was performed by a “technician” but could not provide any documentation. Upon opening, the same half job of easy to reach components replaced. Great sounding amplifier, when service and calibration correctly completed. Highly recommended. These were not cheap in the day – the first owner having bought new.
This Pioneer SA-7100 is highly recommended also. Real nice warm sound. Tasked with source and fit of a power switch after it had broken. Found another internal half job, easy to reach components replaced, but none of the essential. Point to point wiring is best left to the experts, which I assume is why whoever worked on it, didnt do it. Crucially, the calibration procedure required re terminating point to point wiring. It was obvious it had never been done since production.
Whilst all these did “work”, the sound difference is noticeable after correct preventative maintenance and calibration performed. The performance difference wont be noticeable to an owner, but if you want them to last decades to come, the difference between a correctly serviced amplifier and one that isnt, is huge. Concise calibration and components performing to their specifications, not ones edging towards peak operating tolerance, are crucial to the life span of an amplifier, and also the output performance.
In conclusion, always ask for documentation when buying a second hand device that is sold as “serviced”. Whilst the parts replaced and work performed is really only understood by a technician, JZ services provides photos of the internal breakdown when performing large jobs. A laymans explanation can then be provided, as the internal pictures provide some context. Peace of mind that the work charged for has been performed – and always interesting to see the inside on ones amplifier.