Turning on your DSS with an active signal, yet it won't switch on?
Have no IR remote control?
I fought with this for weeks, until I found out most 'normal' S/PDIF sources ground the LF frequency range where the DSS signal is active, thus blocking the device startup logic. One capacitor fixes it!
This amplifier from the mid 1970s, as any 40 year old, needed a health check-up (including the finger in the you know what). As it turned out, some minor repairs were needed. Now it is ready for another 40 years of playing 70s rock.
30 year old relays have been shown to go bad in these speakers, exhibiting a high contact resistance which manifests in very unstable / weak HF sound. You don't need a super audiophile relay, just a standard 36V DPDT or SPDT relay. The PCB has holes for either type. Upgrade is a doddle.
With the help of a couple of logic analyzers and the service manual we reverse engineer the internal logic board comms and the inter-loudspeaker DSS signal. With this information, we now have a full set of specifications for the replacement DSP board, a replacement upsampler as well as a specification to interact with the loudspeaker externally through the DSS protocol, enabling e.g. a subwoofer development.