Forgive me for being slow and having a late response but I REALLY appreciate your research into this and the detail.Sir MobiusOne . . . . .
( Now . . . . let's just see if we can get you all caught up in a Mobius Loop. )
With what I can JUST see / fathom from that supplied photo.
The NON blowing of that fuse is GOOD.
Its power supply circuitry may have just got "weak and lazy" from time of use.
If being yours from day one . . . and not a curb find ! ! ! . . . .how old is it being now ?
I am finding minus ZERO, freebie . . . . . schematic / tech svc manuals on this Sansui.
CIRCUIT ANALYSIS . . . .
AC Power comes in as the GREEN line and passes thru glass fuse and then into a few EMI filtering components and then into 4 power diodes which then have DC voltage coming out as the now RED line and it goes into a WHITE BLOCK 1.2 ohm line surge resistor.
That resistors other end goes into the MAIN filter cap as its + lead as the large black cylinder at far corner end chassis.
And then that voltage might ? pass to the RED STAR resistor and then out of it, YOU can confirm by examining its connecting foil path .
Then that supply voltage passes into a primary winding of the power transformer . . . at the end of that RED line.
The end of that primary winding comes out as the ORANGE line and then goes to a power switching transistor / or / FET at the end of the ORANGE line.
Pulses of variable frequency / and / or / widths drive that power transistor and it in turn drives the power transformer primary . . . . the sampling of one winding of the transformer secondary, feedback, and how it relates to power consumption changes, such that pulse changes fed to that power device . . . . . will hold all to an appropriate, regulated level.
The YELLOW ARROW output arrow is for the power transformers multiple secondary windings which will be rectified by the RED DOT diodes to then feed lower voltage DC to their companion filter caps . . as they, being the ones RED STARRED in the YELLOW BOXED area.
Sound KLAXXON horn . . . three LONG and LOUD bursts . . . . to alert for testing . . . . .
MARK UP . . . . . . . of . . . . . . TECHNO REFERENCING . . . . .
HOWTOMAKEEANDDOTESTEE-TESTEE
First lets just see if that just described power supply is working . . . . since its tasked / committed for 24 hrs a day operation.
If the AC line plug is plugged in, its supposed to be working.
Take meter in hand and set up to read DC voltage, and I would expect the anticipated voltage range to be at a max of 50 VDC. .
If yours is being auto ranging . . .it does that adjustment aspect for you.
TESTING POINTS . . . .
Note the tuner housing that my BLACK . . . . . CIRCLE-STAR is identifying.
That would be a good COLD ground reference to stab your BLACK lead meter probe into / or a clip lead into.
Extreme top left corner, inside of the YELLOW rectangle, is a hefty diode . .RED dotted . . . and I expect its SILVER band end is
being one hefty current supply of voltage output .
Actually, it may have a like companion diode assisting it, as the diode being just below it.
Possibly, with that supply then feeding to the largest E-Caps located over to the right .
Alternate OTHER derived supply's could be the silver band end of the bottom left bottom corners diode.
Also the encircled by capacitors diode, located at the 2 o clock position from the MISSING E-capacitor on the board.
(Matter of fact, I believe that I can also see a SECOND like diode, being just above that one, include the testing of its silver band also.)
Probe those silver banded diode ends for any voltage presence / output.
S O O O O O . . . . . if you can get that all harnessed and plugged into its original operational condition, you can use those test points referenced , to see if you are getting any power supply activity after AC power plug insertion..
If not, we then see if the PRINCIPAL LARGE BLACK E-capacitor in the extreme top corner is getting its 160-170 'ish volts of DC power . . . . .( I sort of expect so)
Standing by . . . and jes' doin' my thang . . . . . .
73's de Edd . . . . . .
Now, I may not be totally perfect . . . . . but, there are certain parts of me that are being absolutely superb.
.
.
UPDATE TWOSir MobiusOne . . . . .
( Now . . . . let's just see if we can get you all caught up in a Mobius Loop. )
With what I can JUST see / fathom from that supplied photo.
The NON blowing of that fuse is GOOD.
Its power supply circuitry may have just got "weak and lazy" from time of use.
If being yours from day one . . . and not a curb find ! ! ! . . . .how old is it being now ?
I am finding minus ZERO, freebie . . . . . schematic / tech svc manuals on this Sansui.
CIRCUIT ANALYSIS . . . .
AC Power comes in as the GREEN line and passes thru glass fuse and then into a few EMI filtering components and then into 4 power diodes which then have DC voltage coming out as the now RED line and it goes into a WHITE BLOCK 1.2 ohm line surge resistor.
That resistors other end goes into the MAIN filter cap as its + lead as the large black cylinder at far corner end chassis.
And then that voltage might ? pass to the RED STAR resistor and then out of it, YOU can confirm by examining its connecting foil path .
Then that supply voltage passes into a primary winding of the power transformer . . . at the end of that RED line.
The end of that primary winding comes out as the ORANGE line and then goes to a power switching transistor / or / FET at the end of the ORANGE line.
Pulses of variable frequency / and / or / widths drive that power transistor and it in turn drives the power transformer primary . . . . the sampling of one winding of the transformer secondary, feedback, and how it relates to power consumption changes, such that pulse changes fed to that power device . . . . . will hold all to an appropriate, regulated level.
The YELLOW ARROW output arrow is for the power transformers multiple secondary windings which will be rectified by the RED DOT diodes to then feed lower voltage DC to their companion filter caps . . as they, being the ones RED STARRED in the YELLOW BOXED area.
Sound KLAXXON horn . . . three LONG and LOUD bursts . . . . to alert for testing . . . . .
MARK UP . . . . . . . of . . . . . . TECHNO REFERENCING . . . . .
HOWTOMAKEEANDDOTESTEE-TESTEE
First lets just see if that just described power supply is working . . . . since its tasked / committed for 24 hrs a day operation.
If the AC line plug is plugged in, its supposed to be working.
Take meter in hand and set up to read DC voltage, and I would expect the anticipated voltage range to be at a max of 50 VDC. .
If yours is being auto ranging . . .it does that adjustment aspect for you.
TESTING POINTS . . . .
Note the tuner housing that my BLACK . . . . . CIRCLE-STAR is identifying.
That would be a good COLD ground reference to stab your BLACK lead meter probe into / or a clip lead into.
Extreme top left corner, inside of the YELLOW rectangle, is a hefty diode . .RED dotted . . . and I expect its SILVER band end is
being one hefty current supply of voltage output .
Actually, it may have a like companion diode assisting it, as the diode being just below it.
Possibly, with that supply then feeding to the largest E-Caps located over to the right .
Alternate OTHER derived supply's could be the silver band end of the bottom left bottom corners diode.
Also the encircled by capacitors diode, located at the 2 o clock position from the MISSING E-capacitor on the board.
(Matter of fact, I believe that I can also see a SECOND like diode, being just above that one, include the testing of its silver band also.)
Probe those silver banded diode ends for any voltage presence / output.
S O O O O O . . . . . if you can get that all harnessed and plugged into its original operational condition, you can use those test points referenced , to see if you are getting any power supply activity after AC power plug insertion..
If not, we then see if the PRINCIPAL LARGE BLACK E-capacitor in the extreme top corner is getting its 160-170 'ish volts of DC power . . . . .( I sort of expect so)
Standing by . . . and jes' doin' my thang . . . . . .
73's de Edd . . . . . .
Now, I may not be totally perfect . . . . . but, there are certain parts of me that are being absolutely superb.
.
.
