There is something going on with the +55V what I can't understand. After repair by Russ of (only) the +15V rail:
The voltages now are112.5, 55.66, 15.1, 4.9 and -6.4
Previously:
Tp1536 [+55] reads46.9
Tp1548 [+15] reads 0
Tp1558 [+5] reads 0.6
Tp1568 [-8] reads 0.48
Tp1518 [110] reads 106.6
I suppose that since 55.66 V is OK the low reading 46.9 V can only be due to a too heavy load at the +55V rail. Based on fallback current limiting Fig.3-12 I estimate the current is about 0.07 A larger than normal and would even be still larger when the +55V would be maintained.
There are several places where due to the fault a larger current from +55V is drawn, but even when +55V is maintained I crudely estimate the total increase to be only some 45 mA. At the same time the vertical final output stage would draw no current, saving some 90 mA.
Can anyone explain what is happening? I probably overlook something. Is it possible that Q4482/4492 (diagram <4a>), or an equivalent in the IC version (<4b>) suffer from avalanche breakdown? The emitters of Q4482/Q4492 are effectively open circuited.
Albert
