Removed and tested with transistor tester Qe15,17 (PNP - ECB - A733) and Qe19,21 (NPN - ECB - C945c)
All tested OK.
I purposefully shorted leads E x C, E x B, B x C, to see what the tester would do, and the tester displayed the shorts each time as two diodes, in various config's
I changed diodes De9, De11, and De15. All removed and new diodes tested correctly. I notice the s/m makes a distinction between IS2076 and IS2076A. Do you know what that is? Maybe wattage? I used 1N4149 for all replacements. A 1N4148 is 200mW, a 1N4149 is 500mW.
I checked De1 and De3 in circuit. Reversed they would bounce up to about a volt, then go OL. This was the same on the Right side De2,4.
I used a 1N5252B for the 24V Zener De1, and i used a 1N5255B 28V Zener for De3.
I checked pin out orientation and what each side connects to by following the traces on the PCB, then comparing that to the s/m. All silkscreening seemed correct, matching the top/bottom and the s/m on all diodes and transistors checked.
Nuts!
I noticed the PCB bottom transistor diagrams for Qe31 and Qe32 had an ECB orientation to the flat side, just like all other transistor diagrams found underneath. The transistors, MJE15032 and33 are actually pin out backwards, at BCE. This makes the transistor mount "backwards" to the picture if you use that convention, but it still mounts to the E, the C and the B of course. I would expect a catastrophic failure here if these were wired wrong. Made my heart jump when I saw it!