Earlier Errata . . . Post # 3 addressee . . . . .should be Reddave101 . . . . . vice esteemed contributor . . . . . Neal
Sir Reddave101 . . . . .
You STILL didn't give the units model number and the only two parts shown on your schema snippet that are being other than solely discrete parts are the
DBF60C-K13 FWB part #'s and the
OSA-SS-212CM5 relay and EVEN they show up being used in so many other AIWA models, that they are not usable for differentiating for a specific Aiwa model .
Seeing that I had dealings in the past with another AIWA unit . . . I am now using its common relevant info in the interim . . . awaiting for your further model info.
Circuit flow . . . .
The power transformers raw ~38 V AC initially goes to GREEN A and thru fuse resistor R122 to GREEN B to then be rectified by D103 to yield a
NEGATIVE ~52VDC and filtering at PINK C E-cap C113 and its adequate voltage rating of 63V .
So that means to CLOSELY watch the installed polarity of all E-caps and diodes associated with this supply .
At the Q112 transistor, being used as a regulator, you have its base being fed from the resultant voltage being acquired by D105, a 30 v zener diode and via the in line R101 / R102 voltage divider bridge.
That combo results in an ~ NEGATIVE 40 VDC then being present at the emitter of Q112.
That regulated NEGATIVE DC voltage then flows on down the PINK E path to input into Q111 , used as a gyrator/ capacitive multiplier, its base gets a reduced sample of D105 zener reference diode voltage via series inserted R103 and also has C114 filter tied into that PINK F junction.
( Take note that the -29V to -29.6V voltage difference is being well covered with the specified 10V rated cap. )
Transistor conduction lets Q111 emitter - collector have a junction loss and a resultant ~NEGATIVE 29.1 present at Q111 emitter PINK G.
There is then a series inserted 10 ohm current limiting resistor R104 , to then release your regulated ~ NEGATIVE 29VDC suppply into the units shared <-VFL> supply line to feed two other units
Vacuum Fluorescent Display type of displays.
If you test out this supply WITHOUT those two other units being connected and find it somewhat normal . . . . less their loading effect on being connected .
ANALYSIS . . . . . of the C114 situation
Then we need to examine their circuitry for what fault they must be causing when then being hooked into this supply.
In looking at the possibility of what would /?/ could cause a "BLOW UP / MAKE- A -
BOOM-
BOOM " of C114.
Observe that . . . .
The left + terminal of C114 is being directly connected to the <-VFL> supply line or thru a 10 ohm resistor to the emitter of Q111
Pretty much an unbridled, down stream, power path there . . . .
So o o o o o . . . .Observe that . . . . .
The right - terminal of C114 goes two paths, one to R103 4.7k resistor, which at our voltages involved cannot pass enough power to blow C114.
The other path is to the base of Q111 and you also don't get enough power from transistors bases to blow up things connected to it . . .UNLESS . . .
its junction has blown/ fused / melted into the Q111 collector and lets the higher 40V supply line voltage into that C114 E-cap.
So you test Q111 CBE junctions for their conditions..
OR
Now you see why I need this units AIWA model number for its complete /whole schematics for my being able to provide you any further help..
( Ignore the schematics far left side, as that relates to the VFD displays filament supply enabling.)
73's de Edd . . . . .
ZUJ . . . . .Standing by
.