After sending the above reply, mulling over what just happened I kept coming back to three thoughts:
- Hi-rez came back after cleaning the boards in the Mano. So the problem was with the Mano, not with the network or the core, etc. That means this drop out problem likely is also somewhere in the Mano as well.
- The drop out problem came up only after I disturbed the boards and wiring in the Mano. Could it be a loose connection, cold solder joint, broken wire?
- The drop out problem did not happen right away. Only after nearly an hour of operating on hi-rez. Could heat have something to do with the issue?
So of course I went back to inspecting the boards and wiring in the Mano. This time focusing on anything that looked even a little suspect.
- Wires feeding Pi board from power supply board looked very small gauge and fragile. Wire broken in its insulation? – replaced wiring with larger gauge known good wire.
- Where shielded cable to SPDIF connector from Pi board is soldered to board the signal conductor insulation is melted and is shorted or nearly shorted to the shield. Removed bad section and (using a heat sink) resoldered to board.
- Ribbon cable from Pi board to HDMI board folded over several times and jammed between boards. Straightened out cable, checked continuity, applied contact enhancer and reattached.
- Found squares of an unknown thin metallic sheet applied to the two largest ICs on the lower Pi board. Way too close to SMD connections from chips to board. Discarded this then inspected and cleaned the chips.
Put Mano back into the system and at 19:44 last night started playing a 96/24 album I have on my server. From the start, no drop outs. Played for 2 hours on 96/24, 192/24, and CD quality with no drop outs. Also monitored board temperature via the browser link to Ropieee. Lowest temp was an outlier at 48.3C (while playing mostly CD quality music). Highest temp was an outlier at 50.2C. Otherwise the temp range was 49.4C to 49.9C.
Before going to bed, I left it play for another 5 hours on a Qobuz hi-rez playlist. Reviewing the Que this morning showed it played thru the playlist. Since getting up at 8:30AM I have had it playing initially some hi-rez but mostly my playlists which are all CD quality. It is now Noon and there have been no dropouts.