Sir Roger_G e e e e e e e e e
From what has been told to me by your post, see if this info fits your unit.
Also I can differentiate even further, by knowing if your back up battery is using 3 cells or a 9 V battery.
The unit is using a conventional no frills power transformer that generates a basic 15VDC main supply from the
BLUE transformer winding, That divides on down to a 5V logic supply
BUT is being interlocked with having a +10VDC supply presence.
The 10 VDC supply is derived from the
YELLOW transformer winding, as it initially passes as AC down the (
GREEN ARROW PATH) until it reaches the DC rectifier diode D5 and transitions out of it as a DC supply . . . . (
ORANGE ARROW PATH ) ..
That supply then feeds into the U1 3 term regulator with its 10VDC output as the (
YELLOW ARROW PATH ) .
Stop . . . . for an aside observation . . .
That +10VDC supply is also fed aside to initiate the creatig of a +5VDC supply.
It originates at the FWB circuitry of the transformers BLUE winding as a +15 VDC supply and travels down the (DOUBLE RED ARROW PATH) until reaching the collector of pass transistor Q4's collector.
NOTHING happens until your 10VDC supply has come up and created a voltage to divide down at R10 / R13 junction and then having a passage of 5VDC at the emittter of Q4, then its across and down the RED ARROW line to be the switched +5VDC supply leg.
START . . . . . back on the (YELLOW ARROW PATH ) to proceed on the supply path.
Now you mentioned the U402 . . . 4052 signal MUX / selector, so I added it on at the far right side of the schema.
You can then see the +10VDC
YELLOW supply feeds of those two CMOS based devices.
Come back, if this info is not in agreement with your unit or for further queries.
Of the 6 WAVE units within our " clan " only one has required service, in the respect of it needing a new AUDIO output POWER AMP I.C. , due to its randomly going off like a
LOUD firecracker.
Other supplies are being a minus 21V and minus 5 from D1 from the 21VAC supply line and a dedicated AC winding of ~3-4 VAC from the power transformer GRAY winding for the frontal displays filament.
Thaaaaaaassssssit . . . . .
SCHEMATIC SELECTIVE PORTION REFERENCING . . . . . .
https://i.ibb.co/mSfthmq/BOSE-WAVE-Series-III-PS-png.png
73's de Edd . . . . .
A girl, with a very enticing and sultry voice, phoned me and said, " I'm at 1211 Elm St. . . . Come on over, there's nobody home."
I hurriedly went right on over.
Nobody was home !
.
