Can you explain how this power supply works and failed ?

Hello all. Your headache is back.

A power supply outputs its +120V fine. Its +220V output line yields +110V.
That is, C1101 has reversed -10V across it.
Both D1101 an C1101 replaced twice; same result.
Disconnecting the load at the +220V line, still does not work.
The top secondary brown-to-red shows 38VAC
The middle secondary red-to-orange shows 41VAC
The bottom secondary orange-to-yellow shows 90VAC
Bridge +to- shows 164V.
Bridge ~to~ shows 132VAC
+8V; -8V are solid healthy.
Nothing is hot, toasted nor blown anywhere.
- What is the purpose of D1106 ?
- Do +8V, -8V presence control/enable its operation ?

It looks weird but it is actually a fairly standard feedback circuit. The difference between this and a 'normal' regulator is the series pass element (TR1102) is in the negative side of the supply instead of the positive one. To work, it relies on the +8V and -8V rails being stable and it monitors the +120C at the junction of R1105 and R1106.

The 220V is a boosted version of the 120V rail and it comes only from the orange/red/brown part of the transformer, essentially they produce 100V and it sits on top of the regulated 120V. For the voltage to be lower than 120V the only possibility is the transformer is open circuit between orange and red or between red and brown, or the 'JP' links are open circuit or D1101 is open circuit. Given that you have checked the components and the transformer, it is most likely the 'JP' are open or one of the connections around them is open.

Brian.

Thank you for the explanation, Brian
Still not fixed. Everything tests good but no +220V :bang:
Windings continuity, secondary voltages, jumpers checked, resoldered everything in the circuit area.
Considering as last resource before framing it and hanging on my hall of shame; building a separate +220V supply and feeding it to the circuit that asks for it. If works, then will evaluate stuffing it in, as spent too many hours on this that should be not complex.